EP4230791A1 - A bleaching process - Google Patents
A bleaching process Download PDFInfo
- Publication number
- EP4230791A1 EP4230791A1 EP22157484.1A EP22157484A EP4230791A1 EP 4230791 A1 EP4230791 A1 EP 4230791A1 EP 22157484 A EP22157484 A EP 22157484A EP 4230791 A1 EP4230791 A1 EP 4230791A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pulp
- enzyme
- xylanase enzyme
- xylanase
- xylan
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 136
- 230000008569 process Effects 0.000 title claims abstract description 127
- 238000004061 bleaching Methods 0.000 title claims abstract description 102
- 101710121765 Endo-1,4-beta-xylanase Proteins 0.000 claims abstract description 382
- 102000004190 Enzymes Human genes 0.000 claims abstract description 375
- 108090000790 Enzymes Proteins 0.000 claims abstract description 375
- 239000000203 mixture Substances 0.000 claims abstract description 149
- 229920001221 xylan Polymers 0.000 claims abstract description 122
- 150000004823 xylans Chemical class 0.000 claims abstract description 118
- 230000009467 reduction Effects 0.000 claims abstract description 64
- 238000011282 treatment Methods 0.000 claims abstract description 46
- 239000007844 bleaching agent Substances 0.000 claims abstract description 44
- 230000002255 enzymatic effect Effects 0.000 claims abstract description 37
- 230000003647 oxidation Effects 0.000 claims abstract description 30
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 30
- 108010031186 Glycoside Hydrolases Proteins 0.000 claims abstract description 22
- 102000005744 Glycoside Hydrolases Human genes 0.000 claims abstract description 22
- 238000000605 extraction Methods 0.000 claims abstract description 21
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 16
- 108090000765 processed proteins & peptides Proteins 0.000 claims description 89
- 102000004196 processed proteins & peptides Human genes 0.000 claims description 85
- 229920001184 polypeptide Polymers 0.000 claims description 84
- 125000003275 alpha amino acid group Chemical group 0.000 claims description 63
- 230000000694 effects Effects 0.000 claims description 57
- 235000001014 amino acid Nutrition 0.000 claims description 55
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 48
- 150000001413 amino acids Chemical class 0.000 claims description 43
- OSVXSBDYLRYLIG-UHFFFAOYSA-N chlorine dioxide Inorganic materials O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims description 29
- 239000012634 fragment Substances 0.000 claims description 19
- FWMNVWWHGCHHJJ-SKKKGAJSSA-N 4-amino-1-[(2r)-6-amino-2-[[(2r)-2-[[(2r)-2-[[(2r)-2-amino-3-phenylpropanoyl]amino]-3-phenylpropanoyl]amino]-4-methylpentanoyl]amino]hexanoyl]piperidine-4-carboxylic acid Chemical compound C([C@H](C(=O)N[C@H](CC(C)C)C(=O)N[C@H](CCCCN)C(=O)N1CCC(N)(CC1)C(O)=O)NC(=O)[C@H](N)CC=1C=CC=CC=1)C1=CC=CC=C1 FWMNVWWHGCHHJJ-SKKKGAJSSA-N 0.000 claims description 18
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 17
- 229910052760 oxygen Inorganic materials 0.000 claims description 17
- 239000001301 oxygen Substances 0.000 claims description 17
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 16
- 125000000151 cysteine group Chemical group N[C@@H](CS)C(=O)* 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 14
- 239000002184 metal Substances 0.000 claims description 14
- 241001477916 Thermopolyspora flexuosa Species 0.000 claims description 13
- 230000009920 chelation Effects 0.000 claims description 10
- 150000002978 peroxides Chemical class 0.000 claims description 6
- 230000013595 glycosylation Effects 0.000 claims description 5
- 238000006206 glycosylation reaction Methods 0.000 claims description 5
- 150000002739 metals Chemical class 0.000 claims description 5
- 241001156739 Actinobacteria <phylum> Species 0.000 claims description 3
- 241000894006 Bacteria Species 0.000 claims description 3
- 241000203580 Streptosporangiaceae Species 0.000 claims description 3
- 241001655321 Streptosporangiales Species 0.000 claims description 3
- 241001133165 Thermopolyspora Species 0.000 claims description 3
- 239000007800 oxidant agent Substances 0.000 claims description 3
- QBWCMBCROVPCKQ-UHFFFAOYSA-N chlorous acid Chemical compound OCl=O QBWCMBCROVPCKQ-UHFFFAOYSA-N 0.000 claims 1
- 229940088598 enzyme Drugs 0.000 description 354
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 39
- 229910052799 carbon Inorganic materials 0.000 description 36
- 238000004076 pulp bleaching Methods 0.000 description 25
- 229920005610 lignin Polymers 0.000 description 20
- 239000000460 chlorine Substances 0.000 description 17
- 238000005406 washing Methods 0.000 description 17
- 108090000623 proteins and genes Proteins 0.000 description 16
- 230000002829 reductive effect Effects 0.000 description 16
- 239000000126 substance Substances 0.000 description 15
- 239000004155 Chlorine dioxide Substances 0.000 description 14
- 125000000539 amino acid group Chemical group 0.000 description 14
- 102000004169 proteins and genes Human genes 0.000 description 14
- 238000006467 substitution reaction Methods 0.000 description 14
- 239000000463 material Substances 0.000 description 13
- 235000018102 proteins Nutrition 0.000 description 13
- 239000002023 wood Substances 0.000 description 13
- 230000003197 catalytic effect Effects 0.000 description 12
- 239000002655 kraft paper Substances 0.000 description 11
- 239000000243 solution Substances 0.000 description 11
- 229920001131 Pulp (paper) Polymers 0.000 description 10
- 239000011122 softwood Substances 0.000 description 10
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 9
- 229910052801 chlorine Inorganic materials 0.000 description 9
- 238000003860 storage Methods 0.000 description 9
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 8
- 238000002203 pretreatment Methods 0.000 description 8
- 108010029541 Laccase Proteins 0.000 description 7
- 238000005282 brightening Methods 0.000 description 7
- 150000001720 carbohydrates Chemical group 0.000 description 7
- -1 elemental chlorine Chemical compound 0.000 description 7
- 238000005259 measurement Methods 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- 230000035484 reaction time Effects 0.000 description 7
- 239000004094 surface-active agent Substances 0.000 description 7
- 239000002253 acid Substances 0.000 description 6
- 238000002474 experimental method Methods 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 229920001282 polysaccharide Polymers 0.000 description 6
- 239000005017 polysaccharide Substances 0.000 description 6
- 108010059892 Cellulase Proteins 0.000 description 5
- 244000166124 Eucalyptus globulus Species 0.000 description 5
- 239000000872 buffer Substances 0.000 description 5
- 235000014633 carbohydrates Nutrition 0.000 description 5
- 239000000835 fiber Substances 0.000 description 5
- 150000004804 polysaccharides Chemical class 0.000 description 5
- 239000006228 supernatant Substances 0.000 description 5
- 239000000725 suspension Substances 0.000 description 5
- SRBFZHDQGSBBOR-IOVATXLUSA-N D-xylopyranose Chemical compound O[C@@H]1COC(O)[C@H](O)[C@H]1O SRBFZHDQGSBBOR-IOVATXLUSA-N 0.000 description 4
- 108030002463 Dye decolorizing peroxidases Proteins 0.000 description 4
- 108010001817 Endo-1,4-beta Xylanases Proteins 0.000 description 4
- 240000000731 Fagus sylvatica Species 0.000 description 4
- 235000010099 Fagus sylvatica Nutrition 0.000 description 4
- 239000004471 Glycine Substances 0.000 description 4
- 102220541617 HLA class II histocompatibility antigen, DQ beta 1 chain_A23S_mutation Human genes 0.000 description 4
- 108010054320 Lignin peroxidase Proteins 0.000 description 4
- 108010059896 Manganese peroxidase Proteins 0.000 description 4
- 102000003992 Peroxidases Human genes 0.000 description 4
- 108030002454 Versatile peroxidases Proteins 0.000 description 4
- 229920002522 Wood fibre Polymers 0.000 description 4
- 108010055059 beta-Mannosidase Proteins 0.000 description 4
- 239000011121 hardwood Substances 0.000 description 4
- 108010038196 saccharide-binding proteins Proteins 0.000 description 4
- 239000002025 wood fiber Substances 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 229920002488 Hemicellulose Polymers 0.000 description 3
- 108091028043 Nucleic acid sequence Proteins 0.000 description 3
- 108091005804 Peptidases Proteins 0.000 description 3
- 239000004365 Protease Substances 0.000 description 3
- 108010076504 Protein Sorting Signals Proteins 0.000 description 3
- 101000666756 Thermoclostridium stercorarium Endo-1,4-beta-xylanase A Proteins 0.000 description 3
- 239000002518 antifoaming agent Substances 0.000 description 3
- 229940106157 cellulase Drugs 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 239000013530 defoamer Substances 0.000 description 3
- 239000003599 detergent Substances 0.000 description 3
- 239000002270 dispersing agent Substances 0.000 description 3
- 239000003995 emulsifying agent Substances 0.000 description 3
- 239000002657 fibrous material Substances 0.000 description 3
- 230000006870 function Effects 0.000 description 3
- 108020001507 fusion proteins Proteins 0.000 description 3
- 102000037865 fusion proteins Human genes 0.000 description 3
- 150000004820 halides Chemical class 0.000 description 3
- 239000008274 jelly Substances 0.000 description 3
- 244000005700 microbiome Species 0.000 description 3
- 238000005063 solubilization Methods 0.000 description 3
- 230000007928 solubilization Effects 0.000 description 3
- 241000894007 species Species 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 125000000969 xylosyl group Chemical group C1([C@H](O)[C@@H](O)[C@H](O)CO1)* 0.000 description 3
- 108010011619 6-Phytase Proteins 0.000 description 2
- 241000609240 Ambelania acida Species 0.000 description 2
- 239000004382 Amylase Substances 0.000 description 2
- 102000013142 Amylases Human genes 0.000 description 2
- 108010065511 Amylases Proteins 0.000 description 2
- 101710152845 Arabinogalactan endo-beta-1,4-galactanase Proteins 0.000 description 2
- 102100032487 Beta-mannosidase Human genes 0.000 description 2
- 241000196324 Embryophyta Species 0.000 description 2
- 101710147028 Endo-beta-1,4-galactanase Proteins 0.000 description 2
- 108090000371 Esterases Proteins 0.000 description 2
- 108050006227 Haem peroxidases Proteins 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 108090001060 Lipase Proteins 0.000 description 2
- 102000004882 Lipase Human genes 0.000 description 2
- 239000004367 Lipase Substances 0.000 description 2
- 108010074633 Mixed Function Oxygenases Proteins 0.000 description 2
- 102000008109 Mixed Function Oxygenases Human genes 0.000 description 2
- 101710163270 Nuclease Proteins 0.000 description 2
- 102000004316 Oxidoreductases Human genes 0.000 description 2
- 108090000854 Oxidoreductases Proteins 0.000 description 2
- 108010059820 Polygalacturonase Proteins 0.000 description 2
- 102100037486 Reverse transcriptase/ribonuclease H Human genes 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 108010061261 alpha-glucuronidase Proteins 0.000 description 2
- 235000019418 amylase Nutrition 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- PYMYPHUHKUWMLA-UHFFFAOYSA-N arabinose Natural products OCC(O)C(O)C(O)C=O PYMYPHUHKUWMLA-UHFFFAOYSA-N 0.000 description 2
- 239000010905 bagasse Substances 0.000 description 2
- SRBFZHDQGSBBOR-UHFFFAOYSA-N beta-D-Pyranose-Lyxose Natural products OC1COC(O)C(O)C1O SRBFZHDQGSBBOR-UHFFFAOYSA-N 0.000 description 2
- 108010047754 beta-Glucosidase Proteins 0.000 description 2
- 102000006995 beta-Glucosidase Human genes 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 108010089934 carbohydrase Proteins 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 235000019398 chlorine dioxide Nutrition 0.000 description 2
- 108010005400 cutinase Proteins 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- YERABYSOHUZTPQ-UHFFFAOYSA-P endo-1,4-beta-Xylanase Chemical compound C=1C=CC=CC=1C[N+](CC)(CC)CCCNC(C(C=1)=O)=CC(=O)C=1NCCC[N+](CC)(CC)CC1=CC=CC=C1 YERABYSOHUZTPQ-UHFFFAOYSA-P 0.000 description 2
- 108010093305 exopolygalacturonase Proteins 0.000 description 2
- 230000014509 gene expression Effects 0.000 description 2
- 229910052736 halogen Inorganic materials 0.000 description 2
- 150000002367 halogens Chemical class 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 230000003301 hydrolyzing effect Effects 0.000 description 2
- 230000002779 inactivation Effects 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 235000019421 lipase Nutrition 0.000 description 2
- 230000009456 molecular mechanism Effects 0.000 description 2
- 230000035772 mutation Effects 0.000 description 2
- 125000003729 nucleotide group Chemical group 0.000 description 2
- 239000005416 organic matter Substances 0.000 description 2
- 108010087558 pectate lyase Proteins 0.000 description 2
- 230000002351 pectolytic effect Effects 0.000 description 2
- 108040007629 peroxidase activity proteins Proteins 0.000 description 2
- 229940085127 phytase Drugs 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 102220170494 rs10747783 Human genes 0.000 description 2
- 102200001738 rs72552724 Human genes 0.000 description 2
- 238000002741 site-directed mutagenesis Methods 0.000 description 2
- 239000010902 straw Substances 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- LENZDBCJOHFCAS-UHFFFAOYSA-N tris Chemical compound OCC(N)(CO)CO LENZDBCJOHFCAS-UHFFFAOYSA-N 0.000 description 2
- 108010083879 xyloglucan endo(1-4)-beta-D-glucanase Proteins 0.000 description 2
- WDMUXYQIMRDWRC-UHFFFAOYSA-N 2-hydroxy-3,4-dinitrobenzoic acid Chemical compound OC(=O)C1=CC=C([N+]([O-])=O)C([N+]([O-])=O)=C1O WDMUXYQIMRDWRC-UHFFFAOYSA-N 0.000 description 1
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 1
- 244000283070 Abies balsamea Species 0.000 description 1
- 235000007173 Abies balsamea Nutrition 0.000 description 1
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 1
- 235000017491 Bambusa tulda Nutrition 0.000 description 1
- 101710104295 Beta-1,4-xylanase Proteins 0.000 description 1
- 235000018185 Betula X alpestris Nutrition 0.000 description 1
- 235000018212 Betula X uliginosa Nutrition 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- 229920003043 Cellulose fiber Polymers 0.000 description 1
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 1
- 108020004705 Codon Proteins 0.000 description 1
- 229920000875 Dissolving pulp Polymers 0.000 description 1
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 1
- 240000000797 Hibiscus cannabinus Species 0.000 description 1
- 102000004157 Hydrolases Human genes 0.000 description 1
- 108090000604 Hydrolases Proteins 0.000 description 1
- QNAYBMKLOCPYGJ-REOHCLBHSA-N L-alanine Chemical compound C[C@H](N)C(O)=O QNAYBMKLOCPYGJ-REOHCLBHSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 108010052285 Membrane Proteins Proteins 0.000 description 1
- 102000018697 Membrane Proteins Human genes 0.000 description 1
- 206010028400 Mutagenic effect Diseases 0.000 description 1
- QPCDCPDFJACHGM-UHFFFAOYSA-N N,N-bis{2-[bis(carboxymethyl)amino]ethyl}glycine Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(=O)O)CCN(CC(O)=O)CC(O)=O QPCDCPDFJACHGM-UHFFFAOYSA-N 0.000 description 1
- 229920001046 Nanocellulose Polymers 0.000 description 1
- 108700026244 Open Reading Frames Proteins 0.000 description 1
- 102000035195 Peptidases Human genes 0.000 description 1
- 244000082204 Phyllostachys viridis Species 0.000 description 1
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 1
- 241000218657 Picea Species 0.000 description 1
- 235000008331 Pinus X rigitaeda Nutrition 0.000 description 1
- 241000018646 Pinus brutia Species 0.000 description 1
- 235000011613 Pinus brutia Nutrition 0.000 description 1
- 241000209504 Poaceae Species 0.000 description 1
- 241000219000 Populus Species 0.000 description 1
- 241000183024 Populus tremula Species 0.000 description 1
- 235000016976 Quercus macrolepis Nutrition 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 241000499912 Trichoderma reesei Species 0.000 description 1
- 239000007983 Tris buffer Substances 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 1
- 125000002777 acetyl group Chemical group [H]C([H])([H])C(*)=O 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 235000004279 alanine Nutrition 0.000 description 1
- 125000000089 arabinosyl group Chemical group C1([C@@H](O)[C@H](O)[C@H](O)CO1)* 0.000 description 1
- 230000001580 bacterial effect Effects 0.000 description 1
- 239000011425 bamboo Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 235000013339 cereals Nutrition 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 238000010411 cooking Methods 0.000 description 1
- 235000005822 corn Nutrition 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 238000012217 deletion Methods 0.000 description 1
- 230000037430 deletion Effects 0.000 description 1
- VDQVEACBQKUUSU-UHFFFAOYSA-M disodium;sulfanide Chemical compound [Na+].[Na+].[SH-] VDQVEACBQKUUSU-UHFFFAOYSA-M 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000012407 engineering method Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 230000009088 enzymatic function Effects 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000000855 fermentation Methods 0.000 description 1
- 230000004151 fermentation Effects 0.000 description 1
- 239000013505 freshwater Substances 0.000 description 1
- 230000002538 fungal effect Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000002068 genetic effect Effects 0.000 description 1
- 125000002367 glucuronosyl group Chemical group 0.000 description 1
- 229920000140 heteropolymer Polymers 0.000 description 1
- 231100000086 high toxicity Toxicity 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000011630 iodine Substances 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 108091005763 multidomain proteins Proteins 0.000 description 1
- 238000002887 multiple sequence alignment Methods 0.000 description 1
- 231100000243 mutagenic effect Toxicity 0.000 description 1
- 230000003505 mutagenic effect Effects 0.000 description 1
- 239000002773 nucleotide Substances 0.000 description 1
- 150000001451 organic peroxides Chemical group 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000000643 oven drying Methods 0.000 description 1
- 239000006174 pH buffer Substances 0.000 description 1
- 239000000123 paper Substances 0.000 description 1
- 239000010893 paper waste Substances 0.000 description 1
- 239000011087 paperboard Substances 0.000 description 1
- 239000000813 peptide hormone Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 108091033319 polynucleotide Proteins 0.000 description 1
- 239000002157 polynucleotide Substances 0.000 description 1
- 102000040430 polynucleotide Human genes 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000002708 random mutagenesis Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 125000003607 serino group Chemical group [H]N([H])[C@]([H])(C(=O)[*])C(O[H])([H])[H] 0.000 description 1
- 238000002415 sodium dodecyl sulfate polyacrylamide gel electrophoresis Methods 0.000 description 1
- 229910052979 sodium sulfide Inorganic materials 0.000 description 1
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 125000004434 sulfur atom Chemical group 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- SPOMEWBVWWDQBC-UHFFFAOYSA-K tripotassium;dihydrogen phosphate;hydrogen phosphate Chemical compound [K+].[K+].[K+].OP(O)([O-])=O.OP([O-])([O-])=O SPOMEWBVWWDQBC-UHFFFAOYSA-K 0.000 description 1
- WCTAGTRAWPDFQO-UHFFFAOYSA-K trisodium;hydrogen carbonate;carbonate Chemical compound [Na+].[Na+].[Na+].OC([O-])=O.[O-]C([O-])=O WCTAGTRAWPDFQO-UHFFFAOYSA-K 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Images
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
- D21C5/005—Treatment of cellulose-containing material with microorganisms or enzymes
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
- D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/16—Bleaching ; Apparatus therefor with per compounds
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/005—Microorganisms or enzymes
Definitions
- the present disclosure generally relates to bleaching of pulp.
- the disclosure relates particularly, though not exclusively, to an improved process of delignification of pulp in the presence of GH11 xylanase enzyme at high pH and high temperature.
- Bleached pulp is used to make, for example, paper, paperboard, tissue, dissolving pulp, fluff pulp, market pulp, and recently also new products defined as MFC (Micro Fibrillated Cellulose) and NCF (Nano Cellulose Fibers). Pulp is commonly processed by kraft pulping, wherein free cellulose fibers are obtained by dissolving the lignin in alkaline cooking liquor. The residual lignin and lignin derivatives attached to carbohydrate moieties of the pulp give the pulp undesired brown color, and the pulp is traditionally thereafter bleached.
- MFC Micro Fibrillated Cellulose
- NCF Nano Cellulose Fibers
- the pulp bleaching process can be divided into two subsequent sections: delignification and brightening.
- delignification the wood components lignin and hemicelluloses are at least partly dissolved and removed from the pulp via the use of bleaching chemicals.
- the brightness of the pulp is also increased.
- subsequent brightening section the delignified pulp is treated with bleaching chemicals that will react with chromophores leading to their elimination thereby producing bleached or white pulp.
- the delignification has at least two stages, an oxidation step wherein a bleaching agent is added, and an alkaline extraction step, wherein an alkaline agent is added.
- the oxidation step can be preceded by an oxygen-delignification step (O), wherein oxygen is mixed into the pulp, and wherein a large portion of the lignin within the pulp is removed.
- O oxygen-delignification step
- the bleaching agent added in the oxidation step is further contributing to the lignin removal, and several bleaching agents can be employed in the process.
- Pulp has been traditionally bleached (whitened) with chemicals comprising chlorine, such as elemental chlorine, which enables the creation of chlorinated organic by-products having toxic and mutagenic effects in the environment. Therefore, elemental chlorine-free methods for pulp bleaching have been utilized, to avoid the release of chlorogenic compounds.
- a totally chlorine free bleaching utilizes bleaching agents, such as hydrogen peroxide.
- Pulp comprises a complex mixture of polysaccharides, mainly cellulose, lignin and hemicellulose.
- Xylan is an important component of hemicellulose.
- the chemical composition of xylan comprises a polysaccharide main chain of ⁇ -1,4-linked xylose residues, and often side chains which can be, for example, acetyl, arabinosyl and/or glucuronosyl groups.
- xylan holds back substances such as lignin and hexenuronic acid, that consume bleaching chemicals. Such substances can be chemically bound to xylan and/or physically entrapped in xylan.
- Hexenuronic acid is formed in pulp material digesters.
- Xylanases are enzymes that digest xylans resulting in mixtures of smaller xylan fragments. Xylanases that hydrolyze ⁇ -1,4-linked xylose residues, particularly endo-1,4- ⁇ -xylanases (EC 3.2.1.8) have been classified in glycoside hydrolase families GH5, GH8, GH10, GH11, GH30 and GH43 in the CAZy database.
- the xylanases of different glycoside hydrolase families differ structurally from each other, the GH11 xylanase enzymes having a ⁇ -jelly roll structure, the GH5, GH10 and GH30 xylanase enzymes having a ( ⁇ / ⁇ ) 8 barrel structure, the GH8 xylanase enzymes having a ( ⁇ / ⁇ ) 6 barrel structure, and the GH43 xylanase enzymes having a 5-fold ⁇ -propeller structure.
- Many different xylanases are known, for example in GH10 and GH11 families there are 5949 and 2187 different enzymes, respectively. Additionally, many variants of xylanases found in nature have been engineered.
- a xylanase In pulp bleaching processes, a xylanase shall depolymerize xylan, break the link between xylan and lignin, facilitate lignin reduction and improve the accessibility of bleaching chemicals to lignin, thereby contributing to delignification, bleaching efficiency and final brightness of the pulp.
- pulp bleaching the pulp entering the delignification stage is hot and alkaline, and therefore the xylanases used in such processes must possess exceptionally good stability and activity at biologically challenging conditions of very alkaline pH and high temperature.
- xylanase enzymes which can retain activity and function in a pulp bleaching process, particularly with regard to improving pulp brightness, reduction of bleaching chemical consumption and reduction of toxic chlorine-containing compound generation.
- xylanases with pronounced differences in pulp bleaching performance, pH- and temperature profile, enzyme stability, specific activity and other enzyme properties have been reported, but generally xylanases are not stable and do not perform under very high temperatures and alkaline conditions of pulp bleaching processes. Therefore, there is a need for xylanase enzymes which are both, very thermostable and alkaline-tolerant, and which are active and perform in industrial processes such as pulp bleaching. Therefore, it is an object of the present disclosure to provide a bleaching process with a xylanase enzyme that is able to perform in the said process at high temperature and alkaline pH.
- a bleaching process comprising:
- a suitable xylanase enzyme for the present bleaching process can be selected based on the molecular mechanism underlying pulp bleaching performance of the xylanase enzyme, rather than just xylanase enzyme activity or the release of xylan hydrolysis products from pulp. This is rationalized by a pre-bleaching effect of xylanases, being the result mainly of xylan depolymerization, rather than solubilization.
- GH11 xylanase enzymes that depolymerize xylan without solubilization of xylan are particularly advantageous in a pulp bleaching process, because xylan solubilization may lead to undesirable chemical oxygen demand (COD) increase and pulp yield loss. Therefore, the selection of suitable GH11 xylanase enzyme for pulp bleaching performance should be based on the molecular mechanism underlying the pulp bleaching performance, in addition to and/or instead of the xylanase enzyme activity or the release of xylan hydrolysis products from pulp. When polymers like xylan are depolymerized, the viscosity of a xylan-containing mixture in question is reduced.
- any xylanase induced viscosity reduction in pulp is likely to be small and hardly measurable. It was surprisingly found that xylanase induced viscosity reduction indicating the depolymerization potential of xylanase enzymes, could be measured in xylan-containing mixtures comprising pure or purified xylan, rather than pulp. Furthermore, it was surprisingly found that xylanase induced viscosity reduction is connected to xylanase performance in a pulp bleaching process at high temperature and high pH.
- the bleaching process provides an efficient way to produce delignified and bleached pulp in the presence of the GH11 xylanase enzyme at high temperature and high pH.
- a pulp composition comprising:
- a bleaching process comprising:
- a pulp composition comprising:
- the present bleaching process comprising the GH11 xylanase enzyme is advantageous in reducing the overall amount of bleaching agent used in the pulp bleaching process.
- the present bleaching process is advantageous in reducing the amount of ClO 2 , O 3 , H 2 O 2 or peroxide consumption in the pulp bleaching process.
- the present bleaching process is advantageous in achieving higher pulp brightness and/ or higher bleaching product production with the same amount of bleaching agent used in the pulp bleaching process, when compared to a bleaching process without the GH11 xylanase enzyme.
- the present bleaching process is advantageous in achieving higher pulp brightness and/ or higher bleaching product production with reduced amount of bleaching agent used in the pulp bleaching process, when compared to a bleaching process without the GH11 xylanase enzyme.
- the present bleaching process is advantageous in reducing the production costs of bleached pulp.
- the present bleaching process allows more efficient bleaching of the pulp, resulting in more efficient utilization of wood raw material.
- the present bleaching process is advantageous in integrating the use of the GH11 xylanase enzyme with a high pH- and thermostability to a bleaching process, thereby reducing or avoiding the need to change existing process conditions and/or the setup/hardware commonly used in pulp bleaching.
- the present bleaching process is advantageous in reducing the corrosion, wear and erosion of the metal pulp bleaching tanks, due to reduced need for lowering pulp pH with acidic agents.
- the present bleaching process is advantageous in reducing fresh water consumption of the bleaching process, due to reduced need for additional water washes.
- the present bleaching process is advantageous in reducing the generation of AOX (Adsorbable Organic Halide also known as chloro-organic compounds) which are discharged with the wastewater bleaching effluents.
- AOX Adsorbable Organic Halide also known as chloro-organic compounds
- the present bleaching process is advantageous in reducing the amount of energy needed to increase the temperature of pulp after being washed and before the oxygen delignification or before the oxidation step, due to reduced need for lowering pulp temperature for enzyme treatment.
- Fig. 1 shows a flow chart of the process steps of a delignification bleaching process of pulp according to an example embodiment.
- the process steps X, O, Q inside dashed line boxes indicate optional and/or alternative process steps.
- the invention relates to a bleaching process utilizing a glycoside hydrolase family GH11 xylanase enzyme in a delignification step of the process, said GH11 xylanase enzyme having stability, activity and performance at biologically challenging conditions of high temperature and alkaline pH, resulting in improved bleaching of pulp.
- bleaching process is meant a chemical treatment process where the brightness or whiteness of the pulp is increased by removing chemical elements such lignin and chromophoric double bonds that give color to the pulp.
- delignification is meant the removal and extraction of lignin contained within pulp.
- Kappa number can be used as a measure of lignin content in pulp.
- alkaline extraction step is meant a bleaching step wherein pH of the pulp is increased to a level where oxidized lignin is extracted from the pulp.
- glycoside hydrolase is meant a hydrolase that is capable of hydrolyzing glycosidic bonds between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety.
- glycoside hydrolase family 11 refers to GH11 xylanases according to the definition of the CAZy database, http://www.cazy.org/GH11.html, the GH11 xylanases having a ⁇ -jelly roll structure, the GH11 xylanase enzymes thereby differing structurally from other xylanases.
- xylan refers to matrix polysaccharides or heteropolymers, composed of a repeating ⁇ -1,4-linked xylose residue backbone, with various side-chain groups.
- Xylan polysaccharides can be categorized into classes O-acetylglucuronoxylans (AcGX), O-acetylarabinoxylans (AcAX), Oacetylglucuronoarabinoxylans (AcGAX), and arabinoglucuronoxylans (AGX), based on the substituted side-chain groups.
- Xylan-containing materials comprise plant-based or plant-originating material.
- xylanase denotes a xylanase enzyme defined according to that known in the art as endo-1,4- ⁇ -xylanase, or 4- ⁇ -D-xylan xylanohydrolase, known to catalyze the endohydrolysis of (1 ⁇ 4)- ⁇ -D-xylosidic linkages in xylans.
- Xylanases have the alternative names endo-(1 ⁇ 4)- ⁇ -xylan 4-xylanohydrolase, endo-1,4-xylanase, xylanase, ⁇ -1,4-xylanase, endo-1,4-xylanase, endo- ⁇ -1,4-xylanase, endo-1,4- ⁇ -D-xylanase, 1,4- ⁇ -xylan xylanohydrolase, ⁇ -xylanase, ⁇ -1,4-xylan xylanohydrolase, endo-1,4- ⁇ -xylanase and ⁇ -D-xylanase.
- Xylanases are classified according to the Enzyme Nomenclature as EC 3.2.1.8.
- the term "GH11 xylanase enzyme protein” refers to pure GH11 xylanase enzyme protein.
- the GH11 xylanase enzyme protein can be added at an enzymatic treatment step X as one component of a composition, but in such embodiment also, the term GH11 xylanase enzyme protein refers to pure GH11 xylanase enzyme protein as one of the components of the composition.
- the amount of the GH11 xylanase enzyme protein refers to a dry weight (grams) of the GH11 xylanase enzyme protein, which dry-weight can be determined according to the test procedure described in the examples.
- pulp means water-comprising fibrous material originally obtained from plants.
- the pulp can originate from wood, fiber crops, bagasse, straw, waste paper or rags, or any combination thereof. Therefore, in the context of this application "pulp” can refer to wood pulp originating from wood material, and/or to non-wood pulp, originating from non-wood material.
- wood pulp means water-comprising fibrous material originating from wood material and produced by digesting hard or softwood chips at temperatures above about 120 °C with a solution of sodium hydroxide and sodium sulfide.
- non-wood pulp means water-comprising fibrous material originating from non-wooden materials, produced by digesting said non-wooden materials, such as grasses, cereal straws, corn stalks, bamboo, kenaf, or bagasse, or any combination thereof.
- xylan-containing pulp means wood or non-wood pulp containing xylan.
- wood pulp means wood pulp originating from wood fibers of broadleaved trees such as oak, beech, birch, aspen, eucalyptus and/or poplar.
- softwood pulp means wood pulp originating from wood fibers of needle-bearing trees such as pines, spruce, fir, and/or hemlock.
- kraft pulp means wood pulp produced by the kraft process, also known as the sulfate process, where wood chips are treated with sodium sulfide (Na 2 S) and sodium hydroxide (NaOH).
- thermoostable enzyme or "temperature tolerant enzyme” refers to an enzyme with a good ability to withstand and resist structural changes leading to enzyme inactivation, caused by high temperature such as temperature of 85 °C or higher.
- pH stability of an enzyme or “pH tolerance of an enzyme” describes the enzyme's property to withstand and resist structural changes leading to enzyme inactivation, caused by high pH such as pH of 9.5 or higher, or alternatively, caused by low pH.
- process water any water that is used in the pulp bleaching process.
- process wash water is meant any water that is used for the purpose of washing pulp in the pulp bleaching process.
- viscosity or “relative viscosity” means the viscosity of the indicated material, such as a xylan-containing mixture, a suspension, or a solution.
- a viscosity reduction of a mixture containing GH11 xylanase enzyme and xylan is an indicator of the xylan depolymerization activity of said GH11 xylanase enzyme.
- the viscosity is measured with a rolling-ball viscometer.
- the term "xylan-containing mixture” refers to a mixture which contains xylan and which mixture can refer to a solution, suspension or a mixture of liquid and solids.
- the xylan-containing mixture contains also xylanase enzyme, such as GH11 xylanase enzyme.
- the xylan-containing mixture is suitable for assessing the xylan-degrading activity of a xylanase enzyme. Therefore, the xylan-containing mixture does not contain any substances, which would distort or falsify the assessment of the xylan degrading activity of a xylanase enzyme.
- the xylan-containing mixture must be suitable for assessing the effect the GH11 xylanase enzyme has on the viscosity of the xylan-containing mixture.
- AOX Adsorbable Organic Halides
- COD chemical oxygen demand
- sequence identity means the percentage of exact matches of amino acid residues between two optimally aligned sequences over the number of positions where there are residues present in both sequences.
- corresponding positions or “corresponding amino acid position” means aligning at least two amino acid sequences according to identified regions of similarity or identity as pairwise alignment or as multiple sequence alignment, thereby pairing up the corresponding amino acids.
- xylanase activity refers to the xylan hydrolyzing activity.
- residual xylanase activity is meant a xylanase enzyme activity which is not the initial activity of said enzyme, but which has been changed, optionally decreased, due to process conditions the enzyme in question has been exposed to. Therefore, residual xylanase activity refers to the amount, for example the percentage amount, of initial activity left after exposure to specific process conditions.
- the term "functional fragment” means a fragment or portion of the current GH11 xylanase enzyme polypeptide, which retains the same or substantially the same enzymatic function or effect as the entire GH11 xylanase enzyme polypeptide.
- the term "stability" in context of enzyme or xylanase stability describes the enzyme's property to withstand and/or function in process conditions that are challenging for the activity and functioning of the enzyme in question, such process conditions being, for example, high temperature, pH or radiation, a certain concentration of inorganic salt or an organic solvent, or a specific reaction mixture composition comprising e.g. proteases, stabilizers, builders, surfactants etc.
- the term "stability” reflects the stability of the xylanase according to the disclosure as a function of time, e.g., how much activity is retained when the xylanase is exposed to process conditions that are challenging for the activity and functioning of the enzyme in question.
- Xyn11A denotes a Thermopolyspora flexuosa xylanase from the glycoside hydrolase family 11 (GH11), also named as AM35.
- AM35 denotes the wild-type mature GH11 xylanase, which is the parent polypeptide used for the AM24 polypeptide.
- the amino acids of the mature AM35 protein correspond to the amino acid sequence of SEQ ID NO: 3.
- the AM24 (also called AM24 protein herein) is a truncated form of the xylanase AM35.
- the AM24 protein comprises the catalytic module (core) and lacks the carbohydrate binding module (CBM) and part of the linker region between core and CBM.
- the amino acids of the mature polypeptide of AM24 correspond to the amino acids of the sequence SEQ ID NO: 1, comprising the amino acids D1-L220.
- the "core polypeptide" of AM24 comprises the amino acids D1 - G191 of SEQ ID NO:1, whereas the "inner core polypeptide" of AM24 comprises the amino acids T3 - S180 of SEQ ID NO:1.
- the C31-4 refers to a variant of AM24 comprising the substitutions T3C, A23S, S28I, T30C.
- the amino acids of the mature polypeptide of C31-4 correspond to the amino acids of the sequence SEQ ID NO: 2 comprising the amino acids D1-L220.
- the "core polypeptide" of C31-4 comprises the amino acids D1 - G191 of SEQ ID NO:2, whereas the “inner core polypeptide” of C31-4 comprises the amino acids C3 - S180 of SEQ ID NO:2.
- carbohydrate binding domain refers to specific domain or module in a polypeptide, which is capable in facilitating the binding of the polypeptide to a carbohydrate.
- the term "mature polypeptide” means any polypeptide wherein at least one signal sequence or signal peptide or signal peptide and a putative pro-peptide is cleaved off.
- the "mature polypeptide” of AM24 comprises the amino acids D1 - L220 of SEQ ID NO:1 and the “mature core polypeptide” of AM24 comprises the amino acids D1 - G191 of SEQ ID NO:1.
- a "peptide” and a “polypeptide” are amino acid sequences including a plurality of consecutive polymerized amino acid residues.
- peptides are molecules including up to 20 amino acid residues, and polypeptides include more than 20 amino acid residues.
- the peptide or polypeptide may include modified amino acid residues, naturally occurring amino acid residues not encoded by a codon, and non-naturally occurring amino acid residues.
- a "protein” may refer to a peptide or a polypeptide of any size.
- a protein may be an enzyme, a protein, an antibody, a membrane protein, a peptide hormone, regulator, or any other protein.
- variant means a sequence or a fragment of a sequence (nucleotide or amino acid) inserted, substituted or deleted by one or more nucleotides/amino acids, or which is chemically modified.
- the term variant may in some embodiments also include a variant polypeptide of xylanase, a fusion protein including a variant polypeptide of xylanase, or a recombinant xylanase enzyme.
- xylanase variant and “variant xylanase” and “variant of xylanase” means any xylanase molecule obtained by site-directed or random mutagenesis, insertion, substitution, deletion, recombination and/or any other protein engineering method, which leads to xylanases that differ in their amino acid sequence from the parent xylanase, the parent xylanase being a wild-type xylanase or a xylanase variant itself.
- wild type xylanase refers to a xylanase enzyme with an amino acid sequence found in nature or a fragment thereof.
- the variant encoding gene can be synthesized or the parent gene be modified using genetic methods, e.g. by site-directed mutagenesis, a technique in which one or more than one mutations are introduced at one or more defined sites in a polynucleotide encoding the parent polypeptide.
- disulfide bridge refers to a bond formed between the sulfur atoms of cysteine residues in a polypeptide or a protein. Disulfide bridges can be naturally occurring, or non-naturally occurring, and, for example, introduced by way of amino acid substitution(s).
- catalytic domain or “catalytic module” or “core” or “catalytic core domain” denotes a domain of an enzyme, which may or may not have been modified or altered, but which retains at least part of its original activity.
- linker or "spacer” is meant a polypeptide comprising at least two amino acids which may be present between the domains of a multidomain protein, for example an enzyme comprising a catalytic domain and a binding domain such as a carbohydrate binding module (CBM), or any other enzyme hybrid, or between two proteins or polypeptides produced as a fusion polypeptide, for example a fusion protein comprising two core enzymes.
- CBM carbohydrate binding module
- the fusion protein of a catalytic domain with a CBM is provided by fusing a DNA sequence encoding the catalytic domain, a DNA sequence encoding the linker and a DNA sequence encoding the CBM sequentially into one open reading frame and expressing this construct.
- dry matter or “dry matter pulp” or “O.D. pulp” refers to pulp dried with the oven-drying method, wherein the dry matter pulp is moisture-free, i.e., free of water.
- the dry matter content of oven-dried pulp can be determined according to ISO 638:2008.
- amino acid substitution means an amino acid residue replacement with an amino acid residue that is different than the original amino acid in that specific replacement position.
- amino acid substitution can refer to both, conservative amino acid substitutions and non-conservative amino acid substitutions, which means the amino acid residue is replaced with an amino acid residue having a similar side chain (conservative), or a different side chain (non-conservative), as the original amino acid residue in that place. Substitutions are described using of the following nomenclature: amino acid residue in the protein scaffold; position; substituted amino acid residue(s). According to this nomenclature the substitution of, for instance, a single residue of alanine to serine residue at position 23 is indicated as Ala23Ser or A23S.
- the term “comprising” includes the broader meanings of “including”, and “containing”, as well as the narrower expressions “consisting of” and “consisting only of”.
- the words “comprise”, “include”, and “contain” are each used as open-ended expressions with no intended exclusivity.
- material originating from wood material or non-wood material is bleached in the bleaching process.
- the wood or non-wood material prior to the bleaching process, is digested in a digester, for obtaining pulp.
- the pulp is treated with chemicals to dissolve lignin in the pulp.
- the pulp is hardwood pulp or softwood pulp, or mixture thereof. In an embodiment, the pulp is non-wood pulp. In an embodiment, the pulp is xylan-containing pulp. In an embodiment, the pulp is kraft pulp cooked in alkaline liquor. In an embodiment, the bleaching process comprises multiple steps and one or more water washes in between the steps, or alternatively, each or some of the stages comprises a water wash as a final step of the stage.
- the bleaching process comprises providing pulp and performing a delignification of the pulp by carrying out in the following sequence: a) an enzymatic treatment step (X) comprising contacting the pulp with a glycoside hydrolase family GH11 xylanase enzyme at a pH of at least 9.5 and a temperature of at least 85 °C; b) an oxidation step (D), wherein a bleaching agent is added; c) an alkaline extraction step (E), wherein an alkaline agent is added; and d) recovering bleached pulp.
- a) an enzymatic treatment step (X) comprising contacting the pulp with a glycoside hydrolase family GH11 xylanase enzyme at a pH of at least 9.5 and a temperature of at least 85 °C
- D oxidation step
- E alkaline extraction step
- the GH11 xylanase enzyme used in the bleaching process has an ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 90 °C and pH 10.5, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme is a glycoside hydrolase family 11 xylanase enzyme.
- the GH11 xylanase enzyme has an ability to cause at least 25 %, preferably at least 30 %, more preferably at least 40 % and most preferably at least 50 % reduction in viscosity of the xylan-containing mixture, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme has an ability to cause at least 17 %, preferably at least 20 %, more preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, even more preferably at least 50 %, most preferably at least 60 % reduction in viscosity of a xylan-containing mixture at 85 - 100 °C and at pH 9.5 - 11.5, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme has an ability to cause at least 10 %, preferably at least 20 %, more preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, even more preferably at least 60 %, most preferably at least 70 % reduction in viscosity of a xylan-containing mixture at 85 - 90 °C and at pH 8 - 11, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme has an ability to cause at least 50 %, preferably at least 55 %, more preferably at least 60 %, more preferably at least 65 %, even more preferably at least 70 %, most preferably at least 75 %, reduction in viscosity of a xylan-containing mixture at 85 - 90 °C and at pH 8 - 11, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme has an ability to cause at least 10 %, preferably at least 20 %, more preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, even more preferably at least 50 %, most preferably at least 60 %, reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10 - 11, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme has an ability to cause at least 50 %, preferably at least 55 %, more preferably at least 60 %, more preferably at least 65 %, even more preferably at least 70 %, most preferably at least 75 %, reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10 - 11, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme has an ability to cause at least 20 %, preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, even more preferably at least 60 %, most preferably at least 69 % reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10.5, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme has an ability to cause at least 25 % reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10.5, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme used in the step X has the ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 85 - 100 °C and pH 9.5 - 11.5, compared to the same mixture without any xylanase enzyme.
- the GH11 xylanase enzyme used in the step X has the ability to cause at least 10 %, preferably at least 20 %, more preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, even more preferably at least 60 %, most preferably at least 70 % reduction in viscosity of a xylan-containing mixture at 85 -100 °C and at pH 9.5 -11.5, compared to the same mixture without any xylanase enzyme.
- the ability of the GH11 xylanase enzyme to cause a strong reduction in viscosity of a xylan-containing mixture is an indicator of the enzyme's xylan depolymerisation activity. Therefore, a strong reduction in viscosity of a xylan-containing mixture indicates the GH11 xylanase enzyme used has a high xylan depolymerisation activity. In an embodiment, the stronger the viscosity reduction of the xylan-containing mixture in the presence of the GH11 xylanase enzyme, the higher is the xylan depolymerisation activity of the GH11 xylanase enzyme.
- the xylan depolymerisation activity of the GH11 xylanase is an indicator of the thermostability and pH stability of the said enzyme.
- the xylan depolymerisation activity of the GH11 xylanase at 90°C and pH 10.5 is an indicator of the thermostability and pH stability of the said enzyme.
- a high xylan depolymerisation activity indicates the GH11 xylanase in question is suitable for pulp bleaching with high pH and temperature, such as pH 9 - 12 and a temperature of 85 - 100 °C, preferably pH 9.5 - 11.5 and a temperature of 85 - 100 °C.
- the xylan depolymerization activity of the GH11 xylanase enzyme is tested in a xylan-containing mixture which is not wood pulp.
- the xylan-containing mixture comprises: not more than 0.07 g xylan per ml of said mixture, and not more than 3.0 ⁇ g of the GH11 xylanase enzyme protein per gram of said mixture; and wherein the reduction in viscosity takes place within 20 minutes, preferably within 10 minutes, more preferably within 5 minutes and most preferably within 2 minutes.
- the xylan-containing mixture comprises: 0.07 g/ml or less of xylan, and 3.0 ⁇ g or less of the GH11 xylanase enzyme protein per gram of said mixture.
- the reduction in viscosity of the xylan-containing mixture takes place within 20 minutes preferably within 10 minutes, more preferably within 5 minutes and most preferably within 2 minutes.
- the xylan-containing mixture comprises ⁇ 0.07 g/ml, ⁇ 0.06 g/ml, ⁇ 0.05 g/ml, ⁇ 0.04 g/ml, ⁇ 0.03 g/ml, ⁇ 0.02 g/ml, ⁇ 0.01 g/ml or less of xylan.
- the concentration of GH11 xylanase enzyme in the xylan-containing mixture is ⁇ 3.0, ⁇ 2.9, ⁇ 2.5, ⁇ 2.0, ⁇ 1.9, ⁇ 1.5, ⁇ 1.0, ⁇ 0.5, ⁇ 0.3, or ⁇ 0.1 ⁇ g xylanase enzyme protein per gram of said mixture.
- the viscosity of the xylan-containing mixture is reduced with the GH11 xylanase enzyme within 20 min, 15 min, 10 min, 5 min, 2 min or less.
- the step X comprises contacting the pulp with the GH11 xylanase enzyme at a pH 9.5 - 11.5 and a temperature of 85 - 100 °C.
- the step X comprises contacting the pulp with the GH11 xylanase enzyme at a pH of at least 9.5 and a temperature of at least 85 °C. In an embodiment, the step X comprises a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C. In an embodiment, the pH of the pulp during the step X is 9.5 - 11.5. In an embodiment, the temperature of the pulp during the step X is 85 - 100 °C.
- the GH11 xylanase enzyme is added to the pulp with a pH selected from ⁇ 9.5, ⁇ 10, ⁇ 10.5, ⁇ 11, and 11.5. In an embodiment, the GH11 xylanase enzyme is added to the pulp with a temperature selected from ⁇ 85 °C, ⁇ 90 °C, ⁇ 95 °C, and 100 °C.
- lowering of alkaline pH of the pulp and/or lowering of process temperature prior to addition of the GH11 xylanase enzyme is/are omitted.
- an alkaline pH of the pulp is not lowered with acid and/or acid washing step(s) and/or the temperature of the pulp is not reduced with water prior to addition of the GH11 xylanase enzyme, as the GH11 xylanase enzyme tolerates the high delignification pH and temperature of the bleaching process.
- since lowering of process temperature with excess water prior to addition of the GH11 xylanase enzyme is not necessary, the water consumption of the bleaching process is reduced.
- acid consumption of the bleaching process and the bleaching process hardware wear is reduced.
- the GH11 xylanase enzyme has an ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10.5, compared to the same mixture without any xylanase enzyme, wherein the xylan-containing mixture comprises: ⁇ 0.07 g/ml of xylan, and ⁇ 3.0 ⁇ g of the GH11 xylanase enzyme protein per gram of said mixture; and wherein the reduction in viscosity takes place within 20 minutes.
- the GH11 xylanase enzyme has an ability to cause at least 20 %, preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, even more preferably at least 60 %, most preferably at least 65 % reduction in viscosity of said xylan-containing mixture within 20 minutes at a pH of 10.5 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme protein concentration is ⁇ 3.0 ⁇ g per g of xylan-containing mixture.
- the GH11 xylanase enzyme has an ability to cause at least 10 % reduction in viscosity of xylan-containing mixture within 20 minutes at a pH of 11 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme concentration is 1.9 ⁇ g xylanase protein per g of xylan-containing mixture.
- the GH11 xylanase enzyme has an ability to cause at least 53 % reduction in viscosity of xylan-containing mixture within 20 minutes at a pH of 11 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme concentration is 1.9 ⁇ g xylanase protein per g of xylan-containing mixture.
- the GH11 xylanase enzyme has an ability to cause at least 17 % reduction in viscosity of xylan-containing mixture within 20 minutes at pH of 10 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme concentration is 2.9 ⁇ g xylanase protein per g of xylan-containing mixture.
- the GH11 xylanase enzyme has an ability to cause at least 58 % reduction in viscosity of xylan-containing mixture within 20 minutes at pH of 10 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme concentration is 1.9 ⁇ g xylanase protein per g of xylan-containing mixture.
- the GH11 xylanase enzyme has a residual xylanase activity of at least 25 %, preferably at least 50 % and more preferably at least 75% after 10 min, preferably after 20 min, more preferably after 30 min of the step X. In an embodiment, the GH11 xylanase enzyme has a residual xylanase activity of at least 25 %, preferably at least 50 %, more preferably at least 75 % after 20 min of the step X, wherein the step X comprises a pH 9.5 - 11.5 and a temperature of 85 - 100 °C.
- the GH11 xylanase enzyme has a residual xylanase activity of at least 25 % after 30 min, preferably after 40 min, more preferably after 50 min of the step X, wherein the step X comprises a pH 9.5 - 11.5 and a temperature of 85 - 100 °C.
- the xylanase enzyme retains at least 25 % of its xylanase activity after 20 min at 85°C and at pH 9.5.
- the xylanase enzyme retains at least 25 % of its xylanase activity after 20 min at 100°C and at pH 11.5.
- the GH11 xylanase enzyme has a residual xylanase activity of at least 75 %, preferably at least 80 %, more preferably at least 85 % after at least 30 min at pH 10.9 and a temperature of 85 °C.
- the GH11 xylanase enzyme in a hardwood pulp bleaching process water has a residual xylanase activity of at least 75 %, preferably at least 80 %, more preferably at least 85 % after at least 30 min at pH 10.9 and a temperature of 85 °C.
- the xylanase enzyme has a residual xylanase activity of at least 75 %, preferably at least 80 %, more preferably at least 85 % after at least 30 min at pH 10.5 and a temperature of 85 °C.
- the GH11 xylanase enzyme in a softwood pulp bleaching process water has a residual xylanase activity of at least 75 %, preferably at least 80 %, more preferably at least 85 % after at least 30 min at pH 10.5 and a temperature of 85 °C.
- the bleaching process comprises: providing pulp; performing a delignification of the pulp, by carrying out in the following sequence: (a) an enzymatic treatment step (X) comprising contacting the pulp with the glycoside hydrolase family GH11 xylanase enzyme at a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C, wherein the xylanase enzyme has a residual xylanase activity of at least 25 % after 20 min of step X; (b) an oxidation step (D), wherein a bleaching agent is added; (c) an alkaline extraction step (E), wherein an alkaline agent is added; and (d) recovering delignified pulp.
- an enzymatic treatment step (X) comprising contacting the pulp with the glycoside hydrolase family GH11 xylanase enzyme at a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C, wherein the xylanase enzyme has a
- the pulp is provided to the delignification of the bleaching process from a digester.
- At least 0.01 g, preferably at least 0.1 g, more preferably at least 0.2 g, most preferably at least 0.5 g of the GH11 xylanase enzyme protein is added per 1000 kg of dry matter pulp at the step X.
- the GH11 xylanase enzyme is added to the step X at a concentration of 0.01 - 200 g, or 0.1 - 20 g, or 0.2 - 10 g, or 0.5 - 5 g of the GH11 xylanase enzyme protein per 1000 kg of dry matter pulp. In an embodiment, the concentration of the GH11 xylanase enzyme depends on the type of pulp used.
- the enzymatic treatment step (X) comprises contacting the pulp with the glycoside hydrolase family GH11 xylanase enzyme and at least one further enzyme selected from the group consisting of protease, amylase, cellulase, ⁇ -glucosidase, lipase, xylanase, mannanase, cutinase, esterase, ⁇ -glucuronidase, phytase, nuclease, pectinase, pectinolytic enzyme, pectate lyase, carbohydrase, arabinase, galactanase, xanthanase, xyloglucanase, polysaccharide monooxygenase, laccase, peroxidase and oxidase with or without a mediator, or a combination thereof.
- the glycoside hydrolase family GH11 xylanase enzyme at least one further enzyme selected from the group consisting
- the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a cellulase enzyme. In an embodiment, the enzymatic treatment step X comprises contacting the pulp with the GH11 xylanase enzyme and a mannanase enzyme. In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a peroxidase enzyme. In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a lignin peroxidase enzyme (EC 1.11.1.14).
- the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a manganese peroxidase enzyme (EC 1.11.1.13). In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a versatile peroxidase enzyme (EC 1.11.1.16). In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a dye-decolorizing peroxidase enzyme (EC 1.11.1.19).
- the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a haem peroxidase enzyme. In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a copper-based laccase enzyme (EC 1.10.3.2).
- the bleaching process comprises contacting the pulp with a surfactant, surface-active agent, anti-foaming agent, defoamer, emulsifier, dispersant and/or detergent.
- the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a surfactant, surface-active agent, anti-foaming agent, defoamer, emulsifier, dispersant and/or detergent.
- the enzymatic treatment step (X) comprises contacting pulp with an enzyme composition which comprises one or more enzymatic activities, possibly isolated and purified, from one or more species of a microorganism.
- the enzymes of the enzyme composition may originate from different species, preferably fungal or bacterial species, or they are present in a fermentation product of a one microorganism which acts as a host cell for enzyme production, such as in the production of the GH11 xylanase enzyme, when the microorganism simultaneously produces other enzymes in addition to the GH11 xylanase enzyme.
- the enzymatic treatment step (X) comprises contacting pulp with an enzyme composition comprising the GH11 xylanase enzyme protein.
- the pulp is an aqueous mixture, comprising at least 0.5 - 35 wt-% of pulp fibers, wherein the pulp fibers are wood fibers and/or non-wood fibers.
- the pulp fibers contain xylan, the pulp therefore being xylan-containing pulp.
- the delignification is done in the presence of the GH11 xylanase enzyme, the GH11 xylanase enzyme having high pH and thermostability.
- the contacting of the pulp with the GH11 xylanase enzyme in the step X means the GH11 xylanase enzyme is contacted with the xylan comprised by the pulp.
- the delignification further comprises an oxygen-delignification step (O) before the oxidation step D, wherein oxygen is added at the step O; and wherein the step X is before or after the step O.
- O oxygen-delignification step
- oxygen is added as O 2 gas in the oxygen-delignification step, wherein the step is called O 2 step.
- the duration of the enzymatic treatment step X is at least 2 min, at least 5 min, at least 10 min, at least 15 min, at least 20 min, at least 30 min, at least 1 h, at least 1,5 h, at least 2 h, at least 2,5 h, or at least 3 h. In an embodiment, the duration of the enzymatic treatment step X is 2 min - 3 h, 5 min - 2 h, 15 - 60 min, or 20 - 30 min.
- the temperature of the step X is at least 80 °C, at least 85 °C, at least 90 °C, at least 95 °C, or at least 100 °C.
- the pH of the pulp during the step X is at least 8.5, at least 9.0, at least 9.5, at least 10, at least 10.5, at least 11, at least 11.5 or at least 12.
- the duration of the step O is at least 0.5 h, at least 1h, at least 1.5 h, at least 2 h, at least 2.5 h, or at least 3 h.
- the temperature of the step O is at least 75 °C, at least 80 °C, at least 85 °C, at least 90 °C, at least 95 °C, at least 105 °C, at least 110 °C, at least 115 °C, at least 120 °C, at least 125 °C, or at least 130 °C.
- the pH of the pulp during the step O is at least 9.5, at least 10, at least 10.5, at least 11, at least 11.5, or at least 12. In an embodiment, the pH and the temperature of the pulp can change during the step O.
- the pH of the pulp during the step O is 10 - 12 and/or the temperature is 75 - 130 °C.
- the xylanase enzyme is added to the pulp before the step O as its own enzymatic treatment step X.
- the xylanase enzyme is added to the pulp before the step O, and the xylanase enzyme retains at least 25 % residual xylanase activity during at least 20 min of the enzymatic treatment step X comprising a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C.
- the step O releases high amounts of lignin from the pulp. Therefore, in the embodiments wherein the bleaching process comprises the step X prior to step O, washing the pulp between the step X and the step O is not necessary.
- the GH11 xylanase enzyme is added to the pulp before the step O, the GH11 xylanase enzyme in the pulp retains some of its activity in the step O.
- the xylanase enzyme is added to the pulp after the step O and before the step D as its own enzymatic treatment step X. In an embodiment, the xylanase enzyme is added to the pulp after the step O, and the xylanase enzyme retains at least 25 % residual xylanase activity during at least 20 min of the enzymatic treatment step X comprising a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C.
- the GH11 xylanase enzyme can be added at any stage prior to step D, as long as the step X is done in the presence of the GH11 xylanase enzyme having a residual xylanase activity of at least 25 % after at least 20 min at pH of 9.5 - 11.5 and temperature of 85 - 100 °C.
- the GH11 xylanase enzyme has activity at any pH between 5.6 - 11.5 and/or at any temperature between 55 - 100 °C.
- adding the GH11 xylanase enzyme to the pulp before or after the step O, and before the step D allows performing the step X in a pre-existing storage tank or a storage tower of a pulp processing facility, without the need to build separate processing containers/tanks when integrating the enzymatic treatment step X into a bleaching process of pulp, which process did not contain an enzymatic treatment step X previously.
- each step of the delignification of the bleaching process takes place in a separate tank, as indicated in the Fig. 1 .
- the optional oxygen-delignification step (O) is performed in a separate tank O.
- the enzymatic treatment step (X) can be performed in a separate storage tank S1 and/or S2, before and/or after the step O, respectively. In an embodiment, performing the step X in a separate storage tank S1 and/or S2 allows an adequate retention time for the enzymatic treatment of the pulp.
- the presence of storage tank S1 and/or S2 may not be necessary, as the enzymatic treatment step X can be performed in another process tank preceding in the bleaching process sequence the tank D, wherein the oxidation step D is performed.
- the oxidation step D is performed in a tank D ( Fig. 1 ).
- the pulp is directed from the digester (not shown) directly, or via other tanks, such as storage tanks S1 and/or S2, to the oxidation step in the tank D.
- the bleaching process comprises the step O
- the oxygen-treated pulp is directed from the tank O directly, or via other tanks, such as storage tank S2, to the tank D.
- the pulp is washed in between the tanks O and D, to remove dissolved lignin.
- the bleaching process includes a process sequence comprising the steps O, X, D, and a water washing step of the pulp is performed after the step X, at least part of the wash water comprising the GH11 xylanase enzyme is recycled back to the step O.
- the bleaching process includes a process sequence comprising the steps O, X, D, and a water washing step of the pulp is performed between the steps O and X, washing the pulp between the steps X and D is optional.
- a water washing step of the pulp is performed after the step X, at least part of the wash water comprising the GH11 xylanase enzyme is recycled back to the step O.
- the GH11 xylanase enzyme in the pulp retains some of its activity in the step D, if no washing step is performed between the steps X and D.
- the bleaching agent at the oxidation step D comprises an oxygen-containing oxidizing agent, preferably the bleaching agent is selected from a group consisting of ClO 2 , O 3 , H 2 O 2 , and peroxides. Examples for non-oxygen-containing oxidizing agents are Cl 2 and other halogens.
- the bleaching agent is a chemical compound comprising the element oxygen.
- the bleaching agent is ClO 2 .
- the bleaching agent is H 2 O 2 .
- the bleaching agent is an organic peroxide.
- the bleaching agent is an inorganic peroxide.
- the bleaching agent is O 3 .
- the bleaching agent is ClO 2 and the oxidation step is called step D o .
- the pulp is directed into the tank D for the step D and the bleaching agent is added in the tank D.
- both the GH11 xylanase enzyme and the bleaching agent participate in bleaching the pulp during the bleaching process, and therefore the amount of bleaching agent required in the bleaching process is reduced when compared to a bleaching process without any xylanase enzyme.
- the pulp comprises the GH11 xylanase enzyme with residual activity in the step D, both the GH11 xylanase enzyme and the bleaching agent participating in bleaching the pulp simultaneously.
- the pulp comprises the GH11 xylanase enzyme with residual activity in the step D, and the bleaching agent in the step D is preferably H 2 O 2 .
- the pulp no longer comprises the GH11 xylanase enzyme at the step D, as the enzyme has been removed in a washing step prior to the step D.
- the required amount of bleaching agent in the oxidation step is reduced when compared to a bleaching process without any xylanase enzyme, as the pulp entering the step D is already bleached to some degree in the enzymatic treatment step X.
- at least 5 %, preferably at least 7,5 %, more preferably at least 10 % less of the bleaching agent is used than in a corresponding process without the GH11 xylanase enzyme, for achieving a specific pulp brightness.
- the reduction of the amount of bleaching agent leads to reduction in the amount of Adsorbable Organic Halides (AOX) in a water effluent of the bleaching process and reduced need for effluent water treatment afterwards.
- AOX Adsorbable Organic Halides
- the GH11 xylanase enzyme used in the bleaching process is highly tolerant to high pH and temperature.
- the use of temperature and pH tolerant xylanase enzyme in the bleaching process results in higher pulp brightness when compared to a bleaching process without a xylanase enzyme, or when compared to a process comprising less temperature and pH tolerant xylanase enzyme.
- the use of temperature and pH tolerant xylanase enzyme in the bleaching process results in a reduced need of bleaching agent, when a specific pulp brightness is desired.
- the bleaching agent used is H 2 O 2
- a metal chelation step (Q) for removal of metals is performed prior to the oxidation step D
- the GH11 xylanase enzyme is added to the pulp before, during or after the chelation step Q.
- the step Q comprises washing the pulp with a chelating agent, such as EDTA or DTPA, for removing redox-active metal ions from the pulp.
- the duration of the step Q is the same as the duration of the step X.
- the step Q takes place in a separate metal chelation tank Q, prior to the step D in the bleaching process sequence ( Fig. 1 ).
- the purpose of the step Q is to remove metals from the pulp which reduce the bleaching activity of H 2 O 2 , such metals being, for example, copper, manganese and iron.
- the enzymatic treatment step X of the pulp is performed in the same tank Q as the metal chelation step.
- the enzymatic treatment step X of the pulp is performed in the same tank Q as the metal chelation step, before, after or during the metal chelation step.
- the step X is performed in another tank prior to and/or after the step Q.
- the step Q takes place after the oxygen-delignification is performed to the pulp in the tank O.
- the pulp is directed from metal chelation in the tank Q directly, or via other tanks to the oxidation step in the tank D.
- the pulp is directed from the tank Q to a storage tank (not shown), wherein the enzymatic treatment step X is performed, after which the pulp is directed to the oxidation step in the tank D.
- the pulp is washed in between the steps Q and D, to remove the dissolved metals from the pulp prior to the oxidation step.
- the GH11 xylanase enzyme can be added to the pulp before, during or after the step Q.
- the process comprises a water washing step of the pulp between the step Q and the oxidation step in the tank D.
- at least part of the wash water comprising the GH11 xylanase enzyme with residual activity can be recycled back to the metal chelation in the tank Q, preferably, at least part of the said wash water is recycled back to a pulp washer upstream from the tank Q.
- the GH11 xylanase enzyme can be first added to the pulp in the tank D or in a separate storage tank (not shown) after the washing step, before the addition of the bleaching agent H 2 O 2 .
- the GH11 xylanase enzyme in the pulp can retain some of its activity in the step D.
- the duration of the delignification oxidation step in tank D is at least 0.5 h, at least 1h, at least 1.5 h, at least 2 h, at least 2.5 h, or at least 3 h.
- the temperature of the delignification oxidation step is at least 50 °C, at least 60 °C, at least 70 °C, at least 80 °C, at least 90 °C, or at least 100 °C.
- the pH of the pulp during the delignification oxidation step is 12 or less, 11 or less, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.
- the bleaching agent added in the step D reduces the pH of the pulp after oxidation.
- the pulp is directed to the alkaline extraction step E in the tank E ( Fig. 1 ).
- the bleaching process also includes a water washing step of the pulp between the oxidation step in the tank D and the alkaline extraction step in the tank E.
- the wash water optionally comprising the GH11 xylanase enzyme is recycled back to a water washing step before the step D.
- the bleaching agent at the step D is H 2 O 2
- the xylanase enzyme in the wash water being recycled back into a water washing step still has residual activity and is able to contribute to xylan degradation in the tank D.
- the alkaline agent is added into the alkaline extraction step E in the tank E.
- the alkaline agent of the alkaline extraction step E is selected from NaOH, MgO, or combinations thereof.
- the alkaline agent is a mixture of NaOH and H 2 O 2 , or a mixture of NaOH and O 2 or a mixture of NaOH+O 2 +H 2 O 2 .
- the reduction in the amount of needed ClO 2 as a bleaching agent results into reduced amount of NaOH as an alkaline agent required in the step E.
- the reduction in the amount of NaOH as an alkaline agent results into reduction in the chemical oxygen demand (COD) measure of the bleaching process effluent water.
- the GH11 xylanase enzyme has a higher activity in a delignification process water than in normal tap water, when the process conditions including temperature and pH are the same.
- the process water at the delignification stage induces the enzyme stability.
- the duration of the delignification alkaline extraction step E is at least 0.5 h, at least 1h, at least 1.5 h, at least 2 h, at least 2.5 h, or at least 3 h.
- the temperature of the step E is at least 70 °C, at least 80 °C, at least 90 °C, or at least 100 °C.
- the pH of the pulp during the step E is at least 8, at least 9, at least 9.5, at least 10, at least 10.5, or at least 11.
- the alkaline agent increases the pH of the pulp, the pH of the pulp being alkaline at the beginning of the alkaline extraction step, and less alkaline at the end of the alkaline extraction step.
- At least 1 unit, preferably at least 2 units, more preferably at least 2.5 units higher final brightness of the pulp can be achieved with the current bleaching process, than with a corresponding process without the GH11 xylanase enzyme.
- the delignification of the bleaching process is followed by a brightening section of the delignified pulp, which can also comprise several process steps.
- the brightening section can comprise at least one or more brightening steps (Db, P), wherein a bleaching agent is added, and/or one or more brightening alkaline extraction steps (Eb), wherein an alkaline agent is added.
- the main purpose of the brightening section is not to remove remaining lignin from the pulp but to decolorize remaining lignin, thereby obtaining a higher final brightness.
- the glycoside hydrolase family GH11 xylanase enzyme used in the bleaching process according to the invention can be of various origin.
- the xylanase enzyme used in the bleaching process according to the invention is a wild type xylanase enzyme.
- the xylanase enzyme used in the bleaching process according to the invention is a modified xylanase enzyme, and/or a variant of a wild type xylanase enzyme.
- the GH11 xylanase enzyme originates from a thermophilic bacteria. In an embodiment, the GH11 xylanase enzyme originates from bacteria, preferably from Actinobacteria, more preferably from Streptosporangiales, more preferably from Streptosporangiaceae, even more preferably from Thermopolyspora species, most preferably from Thermopolyspora flexuosa. In an embodiment, the xylanase enzyme originates from the group of terrabacteria. In an embodiment, the xylanase enzyme originates from a phylum of Actinobacteria.
- the xylanase enzyme originates from class of Actinomycetia. In an embodiment, the xylanase enzyme originates from the order of Streptosporangiales. In an embodiment, the xylanase enzyme originates from the family of Streptosporangiaceae. In an embodiment, the xylanase enzyme originates from the genus of Thermopolyspora.
- the GH11 xylanase enzyme originates from Thermopolyspora flexuosa.
- Thermopolyspora flexuosa is meant synonymous to Nonomuraea flexuosa, Nonomuria flexuosa, Nocardia flexuosa, Microtetraspora flexuosa, Acetomadura flexuosa and/or Actinomadura flexuosa.
- the glycoside hydrolase family GH11 xylanase enzyme used in the bleaching process comprises a catalytic core domain and a carbohydrate binding module (CBM), linked together by a linker.
- CBM carbohydrate binding module
- the glycoside hydrolase family GH11 xylanase enzyme used in the bleaching process is a truncated enzyme, comprising a catalytic core domain and a linker domain, or a catalytic core domain and part of a linker domain, whereas a CBM is absent.
- the glycoside hydrolase family GH11 xylanase enzyme used in the bleaching process comprises only a catalytic core domain, whereas a linker domain and a CBM are absent.
- the GH11 xylanase enzyme used in the bleaching process comprises a mature catalytic core domain.
- the GH11 xylanase enzyme is a polypeptide, wherein the polypeptide, or a functional fragment of the polypeptide, has a molecular mass of 15 - 100 kDa, preferably 18 - 70 kDa, more preferably 19 - 40 kDa, even more preferably 20 - 33 kDa.
- the GH11 xylanase enzyme has a molecular mass of 19 - 40 kDa, preferably 20 - 30 kDa, more preferably 23 - 25 kDa, most preferably 24 kDa, calculated from its amino acid sequence without glycosylation.
- the GH11 xylanase enzyme has a ⁇ -jelly roll structure.
- the GH11 xylanase enzyme is a polypeptide, wherein the polypeptide or a functional fragment of the polypeptide has a molecular mass of 31 kDa. In an embodiment, the GH11 xylanase enzyme is a polypeptide, wherein the polypeptide or a functional fragment of the polypeptide has a molecular mass of 27 kDa. In an embodiment, the GH11 xylanase enzyme is a polypeptide, wherein the polypeptide or a functional fragment of the polypeptide has a molecular mass of 24 kDa.
- the molecular mass of the GH11 xylanase enzyme polypeptide or a functional fragment of the polypeptide can be determined by SDS-PAGE. In an embodiment, the molecular mass of the GH11 xylanase enzyme polypeptide or a functional fragment of the polypeptide is calculated from its amino acid sequence without glycosylation. In an embodiment, the GH11 xylanase enzyme polypeptide or a functional fragment of the polypeptide has a molecular mass of 24 kDa, calculated from its amino acid sequence without glycosylation. In an embodiment, the GH11 xylanase enzyme lacks xylosidase and cellulase activity.
- the GH11 xylanase enzyme is a variant polypeptide. In an embodiment, the GH11 xylanase enzyme is a wild type polypeptide.
- the GH11 xylanase enzyme has at least one, or at least two disulfide bridges between two cysteine residues in its amino acid sequence. In an embodiment, the at least one disulfide bridge stabilizes the GH11 xylanase enzyme, thereby increasing the pH stability and thermostability of the GH11 xylanase enzyme.
- the GH11 xylanase enzyme is a polypeptide comprising residues 3C and 30C, the positions of these residues corresponding to the positions 3 and 30 of the SEQ ID NO: 2, and a disulfide bridge being formed between the residues 3C and 30C.
- the GH11 xylanase enzyme is polypeptide comprising at least one disulfide bridge between two cysteine residues in the 1 - 191 amino acid region of the polypeptide, the position of at least one of the two cysteine residues being different from the positions corresponding to positions 3 and 30 of the SEQ ID NO: 2.
- the GH11 xylanase enzyme is polypeptide comprising at least one disulfide bridge between cysteine residues in the 1 - 30 amino acid region of the polypeptide, the positions of the amino acid region corresponding to positions of the SEQ ID NO: 2.
- the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having amino acids corresponding to the amino acids 3 - 180 of SEQ ID NO: 2, or functional fragments thereof; the GH11 xylanase enzyme having at least one disulfide bridge between two cysteine residues of the polypeptide.
- the GH11 xylanase enzyme is polypeptide comprising an amino acid sequence having amino acids corresponding to the amino acids 1 - 191 of SEQ ID NO: 2; or functional fragments thereof, the GH11 xylanase enzyme having at least one disulfide bridge between two cysteine residues of the polypeptide.
- the at least one disulfide bridge stabilizes the GH11 xylanase enzyme, thereby increasing the pH stability and thermostability of the GH11 xylanase enzyme compared to a GH11 xylanase enzyme without a disulfide bridge.
- the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having amino acids corresponding to the amino acids 1 - 191 of SEQ ID NO: 1; the GH11 xylanase enzyme having at least one disulfide bridge between two cysteine residues of the polypeptide, and one or two amino acid substitution(s) at a position/positions corresponding to the position(s) 23 and/or 28 of SEQ ID NO: 1.
- the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with amino acids 1 - 191 of SEQ ID NO: 1.
- the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 80 %, at least 81 %, at least 82 %, at least 83 %, at least 84 %, at least 85 %, at least 86 %, at least 87 %, at least 88 %, at least 89 %, at least 90 %, at least 93 %, at least 95 %, at least 96 %, at least 97 %, at least 98 %, or at least 99% sequence identity with amino acids 1 - 191 of SEQ ID NO: 1.
- the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with the amino acids 3 - 180 of SEQ ID NO: 2, or functional fragments thereof.
- the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with amino acids 1 - 191 of SEQ ID NO: 2, or functional fragments thereof.
- the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 80 %, at least 81 %, at least 82 %, at least 83 %, at least 84 %, at least 85 %, at least 86 %, at least 87 %, at least 88 %, at least 89 %, at least 90 %, at least 93 %, at least 95 %, at least 96 %, at least 97 %, at least 98 %, or at least 99% sequence identity with amino acids 3 - 180 of SEQ ID NO: 2.
- the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with SEQ ID NO: 2.
- the GH11 xylanase enzyme comprises the inner core polypeptide of C31-4.
- the GH11 xylanase enzyme comprises the core polypeptide of C31-4.
- the GH11 xylanase enzyme comprises the mature polypeptide of C31-4.
- the GH11 xylanase enzyme is a variant polypeptide having the amino acid sequence SEQ ID NO: 2.
- the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with the amino acids 3 - 180 of SEQ ID NO: 2, or functional fragments thereof; wherein the amino acid sequence has at least one disulfide bridge between two cysteine residues of the polypeptide.
- the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with amino acids 1 - 191 of SEQ ID NO: 2; wherein the amino acid sequence has at least one disulfide bridge between two cysteine residues of the polypeptide.
- the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 % amino acid sequence identity with amino acids 3 - 180 of SEQ ID NO: 2, wherein the amino acid sequence has at least one disulfide bridge between two cysteine residues of the polypeptide.
- the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with amino acids 3 - 180 of SEQ ID NO: 1, and wherein the amino acid sequence has at least one disulfide bridge between two cysteine residues of the polypeptide, and an amino acid substitution at the position 23 or 28, or at the positions 23 and 28, the positions corresponding to the positions 23 and 28 of the SEQ ID NO: 1.
- the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with SEQ ID NO: 1, and an amino acid substitution at the positions 3, 23 and 30, the amino acid positions corresponding to the positions of the SEQ ID NO: 1.
- the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with SEQ ID NO: 1, and an amino acid substitution at the positions 3, 28 and 30, the amino acid positions corresponding to the positions of the SEQ ID NO: 1.
- the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with SEQ ID NO: 1, and an amino acid substitution at the positions 3 and 30, the amino acid positions corresponding to the positions of the SEQ ID NO: 1.
- a pulp composition comprising: pulp having a pH of at least 9.5, and 0.01 - 200 g, preferably 0.1 - 20 g, more preferably 0.2 - 10 g of glycoside hydrolase family GH11 xylanase enzyme protein per 1000 kg of dry matter pulp; wherein the GH11 xylanase enzyme protein has xylanase activity.
- the GH11 xylanase enzyme which is part of the pulp composition, has an ability to cause at least 20 %, preferably at least 25%, more preferably at least 30%, even more preferably at least 40%, most preferably at least 50% reduction in viscosity of a xylan-containing mixture at 90°C and pH 10.5 compared to the same mixture without any xylanase enzyme, wherein the xylan-containing mixture comprises 0.07 g/ml or less of xylan and 3.0 ⁇ g or less of the GH11 xylanase enzyme protein per gram of said mixture; and wherein the reduction in viscosity takes place within 20 minutes, preferably within 10 minutes, more preferably within 5 minutes and most preferably within 2 minutes.
- the pulp composition has a pH of 9.5 - 11.5 and/or a temperature of 85 - 100 °C. In an embodiment, the pulp composition has a pH of at least 9.5, at least 10, at least 10.5, at least 11, or at least 11.5. In an embodiment, the pulp composition has a temperature of at least 85 °C, at least 90 °C, at least 95 °C, or at least 100 °C.
- the pulp composition comprises an enzyme composition, comprising the GH11 xylanase enzyme and at least one further enzyme selected from the group consisting of protease, amylase, cellulase, ⁇ -glucosidase, lipase, xylanase, mannanase, cutinase, esterase, ⁇ -glucuronidase, phytase, nuclease, pectinase, pectinolytic enzyme, pectate lyase, carbohydrase, arabinase, galactanase, xanthanase, xyloglucanase, polysaccharide monooxygenase, laccase, peroxidase and oxidase with or without a mediator, or a combination thereof.
- an enzyme composition comprising the GH11 xylanase enzyme and at least one further enzyme selected from the group consisting of protease, amylase,
- the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a cellulase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a mannanase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a laccase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a peroxidase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a lignin peroxidase enzyme (EC 1.11.1.14).
- the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a manganese peroxidase enzyme (EC 1.11.1.13). In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a versatile peroxidase enzyme (EC 1.11.1.16). In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a dye-decolorizing peroxidase enzyme (EC 1.11.1.19). In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a haem peroxidase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a copper-based laccase enzyme (EC 1.10.3.2).
- the pulp composition further comprises a surfactant, a surface-active agent, an anti-foaming agent, a defoamer, an emulsifier, a dispersant a detergent, or any combination thereof.
- the pulp composition comprises 0.25 - 4 wt-% of a bleaching agent of the total weight of dry matter pulp, the bleaching agent being selected from ClO 2 , O 3 , H 2 O 2 , and peroxides.
- the xylanases and xylanase variants were designed, made and tested for xylanase enzyme stability, as described in the application EP 20217335 . All the xylanases were expressed in Trichoderma reesei.
- Xylanase enzyme activity was measured as described by Bailey, M.J. and Poutanen, K. 1989 in Appl. Microbiol. Biotechnol. 30:5-10 , but instead of 10 minutes at 50°C and pH 5.3, after 5 minutes at 70°C and pH 7 the amount of reducing carbohydrates released from beech xylan was determined spectrophotometrically using dinitrosalicylic acid and compared to xylose standard solutions.
- Protein amounts of purified enzyme samples were measured by absorption at 280nm. Calculated from amino acid compositions, the xylanases AM24 and C31-4 have a molecular mass without glycosylation of approximately 24 kDa and an absorption of 2.852 at 280 nm, 1 cm cuvette and 1 g pure protein per liter.
- Viscous xylan suspensions were prepared by weighting 7 g beech wood xylan into a 100 ml volumetric flask, adding aqueous pH buffer, stirring and heating until the suspensions were boiling for approximately 20 minutes.
- a buffer containing 7.5 g/l glycine (which equals 0.1 M glycine) and sodium hydroxide was used for pH 10.5 .
- a 0.1 M KH 2 PO 4 - K 2 HPO 4 buffer was used for pH 7.0 a 0.1 M KH 2 PO 4 - K 2 HPO 4 buffer was used.
- the volumetric flask was filled up with buffer to the calibration mark and stirred overnight. The next day these mixtures were centrifuged, and the supernatants transferred to a baker and put into an ultrasonic bath for 15 minutes.
- the xylanase enzyme concentrations of AM24 and C31-4 used in these experiments were approximately 29 and 19 ⁇ g of xylanase enzyme protein per g of applied enzyme solutions, respectively. Because 1 g enzyme solution was mixed with 9 g xylan supernatant, the mixtures injected into the viscosimeter resulted in ten times diluted enzyme concentrations; and the xylan concentration was diluted from 7 g per 100 ml to 6.3 g per 100 ml.
- inactivated C31-4 was prepared by heating enzyme solution C31-4 to boiling for 2 hours, then removing precipitated protein. As described above, 1 g of this solution was mixed with 9 g supernatant for viscosity measurement. As expected, viscosity of this mixture was not decreased, indicating that viscosity reduction was caused by active enzyme. Table 2. Almost no performance difference between enzymes AM24 and C31-4 applied at conditions of 80°C and pH 7.0 was measured. 80°C and pH 7.0 Viscosity [mPa ⁇ s] Relative viscosity Comments without enzyme 2.83 100 % No viscosity reduction, reference AM24 0.68 24 % Strong viscosity reduction C31-4 0.62 22 % Strong viscosity reduction
- Short bleaching sequence XDE (step X, enzyme treatment; step D chlorine dioxide (ClO 2 ) treatment; step E, alkaline extraction with sodium hydroxide) was used to compare the efficiency in bleaching of pre-treatments with AM24 and C31-4 xylanases at high temperature of 90°C.
- the pre-treatments were performed at two pH values, pH 8.3 and pH 10.5.
- the pulp used was oxygen delignified Eucalyptus Kraft pulp from an Asian mill with kappa number 15.5 and brightness 38.0 %-ISO.
- a constant ClO 2 dosage (0.2 X kappa number) was used. Bleaching trials were carried out in bleaching reactors.
- step X the enzyme was deactivated by addition of hot water and immediately adjusting the pH of the pulp suspension to pH value 2.5-3. Brightness and kappa number were analyzed after the step E. Table 7. Results of XDE bleaching using eucalyptus pulp. In the REF samples, no enzyme was added. The enzyme pre-treatments were performed at 90 °C using 60 min reaction time. The aCl denotes active chlorine; ⁇ Br denotes difference in Brightness; and ⁇ kappa denotes a difference in Kappa number.
- Pulp pre-treated with C31-4 at pH 8.3 had 2.8 units higher brightness than the reference pulp and had 1.0 units higher brightness than the pulp treated with AM24.
- the active chlorine (aCI) used at pH 8.3 per ⁇ kappa was 0.2 kg/t and per ⁇ Br 0.07 kg/t lower in the C31-4 treated pulp than in AM24 treated pulp and 0.28 kg/t and 0.19 kg/t, respectively, lower than in the reference pulp (Table 7).
- the measured brightness (%-ISO) increase was significant and revealed that the xylanase enzyme C31-4 application in Kraft pulp was beneficial, and effective at 90°C and pH 10.5.
- the pulp used in the trial was oxygen delignified SW Kraft from Scandinavian mill with following properties: kappa number 25.6, viscosity 1140 ml/g and brightness 26.8 %-ISO.
- the dosing of C31-4 enzyme preparation was approximately 2 g of enzyme protein per ton of pulp. The conditions used in different stages of bleaching are described in Tables 8 - 10.
- the pulp was washed three times after the step X.
- the first wash was done using water at reaction temperature (90 °C), followed by two washes with cold (4°C) water.
- a centrifuge treatment (2600 rpm, 10 s) was performed to remove water and about 10 - 15 g (measured as oven dry) pulp samples were collected for analysis.
- dry matter analysis was done from the C31-4 treated samples using IR-dryer for better adjustment of pulp amount. Kappa number and brightness were analyzed from the pulp samples.
- Pre-treatment Target / used pulp amount g (as o.d.) NaOH dosage target / used (% of pulp) Pulp consistency, target /used, % Temperature (°C) Target Initial pH / end pH Reaction time, min No enzyme 200 / 185.2 2.3 / 2.5 10/9.3 80 10.8/ 10.7 90 C31-4 185 / 159.7 2.3/2.7 10 / 8.6 80 10.7/10.7 90 Table 11. Results from the bleaching trial.
- Softwood Kraft pulp pretreated with C31-4 at pH 10.5 had 2.7 units higher corrected end brightness with the same 5.4 % active chlorine consumption compared to reference pulp (no enzyme used).
- Example 5 High temperature and high pH further application of xylanase in Kraft pulp from softwood
- the bleaching test using softwood pulp and conditions like in Example 4 was repeated with the AM24 and C31-4 xylanases.
- the pulp was washed at pH 11 and 60 °C for about 30 minutes before its characterization and experiments. After the washing step the Kappa number of the pulp was 16.7, viscosity 1050 ml/g and brightness 32.6 %-ISO.
- the dosing of both enzymes (C31-4 and AM24) was 2 g of enzyme protein per ton of pulp.
- the conditions used in the xylanase treatment, bleaching and extraction stages are described in Tables 12 - 14.
- step D Enzyme D dosage*, as act. Cl % on pulp Pulp consistency, % Temp eratur e, °C Initial pH / end pH Reaction time, min Act CI consump tion, % on pulp 1. No enzyme 3.3 9 70 2.8/2.1 30 3.3 2. AM24 3.3 9 70 2.5/1.6 30 3.3 3. C31-4 3.3 9 70 2.7/1.7 30 3.3 Table 14. Conditions at step E Enzyme NaOH dosage, % on pulp Pulp consistency, % Temperature, °C Target Initial pH / end pH Reaction time, min 1. No enzyme 1.5 10 80 10.6/10.6 90 2. AM24 1.5 10 80 10.5/10.4 90 3. C31-4 1.5 10 80 10.7/10.6 90
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Microbiology (AREA)
- Chemical & Material Sciences (AREA)
- Biochemistry (AREA)
- Paper (AREA)
Abstract
A bleaching process of pulp is disclosed comprising performing a delignification of the pulp by carrying out in a following sequence: an enzymatic treatment step comprising contacting the pulp with a glycoside hydrolase family GH11 xylanase enzyme at a pH of at least 9.5 and a temperature of at least 85 °C, an oxidation step wherein a bleaching agent is added, an alkaline extraction step wherein an alkaline agent is added, and recovering bleached pulp, wherein the GH11 xylanase enzyme has an ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 90°C and pH 10.5, compared to the same mixture without any xylanase enzyme.
Description
- The present disclosure generally relates to bleaching of pulp. The disclosure relates particularly, though not exclusively, to an improved process of delignification of pulp in the presence of GH11 xylanase enzyme at high pH and high temperature.
- This section illustrates useful background information without admission of any technique described herein representative of the state of the art.
- Bleached pulp is used to make, for example, paper, paperboard, tissue, dissolving pulp, fluff pulp, market pulp, and recently also new products defined as MFC (Micro Fibrillated Cellulose) and NCF (Nano Cellulose Fibers). Pulp is commonly processed by kraft pulping, wherein free cellulose fibers are obtained by dissolving the lignin in alkaline cooking liquor. The residual lignin and lignin derivatives attached to carbohydrate moieties of the pulp give the pulp undesired brown color, and the pulp is traditionally thereafter bleached.
- The pulp bleaching process can be divided into two subsequent sections: delignification and brightening. In the delignification, the wood components lignin and hemicelluloses are at least partly dissolved and removed from the pulp via the use of bleaching chemicals. During delignification, the brightness of the pulp is also increased. In the subsequent brightening section, the delignified pulp is treated with bleaching chemicals that will react with chromophores leading to their elimination thereby producing bleached or white pulp.
- Typically, the delignification has at least two stages, an oxidation step wherein a bleaching agent is added, and an alkaline extraction step, wherein an alkaline agent is added. Additionally, the oxidation step can be preceded by an oxygen-delignification step (O), wherein oxygen is mixed into the pulp, and wherein a large portion of the lignin within the pulp is removed.
- The bleaching agent added in the oxidation step is further contributing to the lignin removal, and several bleaching agents can be employed in the process. Pulp has been traditionally bleached (whitened) with chemicals comprising chlorine, such as elemental chlorine, which enables the creation of chlorinated organic by-products having toxic and mutagenic effects in the environment. Therefore, elemental chlorine-free methods for pulp bleaching have been utilized, to avoid the release of chlorogenic compounds. A totally chlorine free bleaching utilizes bleaching agents, such as hydrogen peroxide.
- Pulp comprises a complex mixture of polysaccharides, mainly cellulose, lignin and hemicellulose. Xylan is an important component of hemicellulose. The chemical composition of xylan comprises a polysaccharide main chain of β-1,4-linked xylose residues, and often side chains which can be, for example, acetyl, arabinosyl and/or glucuronosyl groups. As a component of pulp, xylan holds back substances such as lignin and hexenuronic acid, that consume bleaching chemicals. Such substances can be chemically bound to xylan and/or physically entrapped in xylan. Hexenuronic acid is formed in pulp material digesters.
- Xylanases are enzymes that digest xylans resulting in mixtures of smaller xylan fragments. Xylanases that hydrolyze β-1,4-linked xylose residues, particularly endo-1,4-β-xylanases (EC 3.2.1.8) have been classified in glycoside hydrolase families GH5, GH8, GH10, GH11, GH30 and GH43 in the CAZy database. The xylanases of different glycoside hydrolase families differ structurally from each other, the GH11 xylanase enzymes having a β-jelly roll structure, the GH5, GH10 and GH30 xylanase enzymes having a (β/α)8 barrel structure, the GH8 xylanase enzymes having a (α/α)6 barrel structure, and the GH43 xylanase enzymes having a 5-fold β-propeller structure. Many different xylanases are known, for example in GH10 and GH11 families there are 5949 and 2187 different enzymes, respectively. Additionally, many variants of xylanases found in nature have been engineered. In pulp bleaching processes, a xylanase shall depolymerize xylan, break the link between xylan and lignin, facilitate lignin reduction and improve the accessibility of bleaching chemicals to lignin, thereby contributing to delignification, bleaching efficiency and final brightness of the pulp. In pulp bleaching, the pulp entering the delignification stage is hot and alkaline, and therefore the xylanases used in such processes must possess exceptionally good stability and activity at biologically challenging conditions of very alkaline pH and high temperature.
- There is an increasing demand for such xylanase enzymes, which can retain activity and function in a pulp bleaching process, particularly with regard to improving pulp brightness, reduction of bleaching chemical consumption and reduction of toxic chlorine-containing compound generation. Several xylanases with pronounced differences in pulp bleaching performance, pH- and temperature profile, enzyme stability, specific activity and other enzyme properties have been reported, but generally xylanases are not stable and do not perform under very high temperatures and alkaline conditions of pulp bleaching processes. Therefore, there is a need for xylanase enzymes which are both, very thermostable and alkaline-tolerant, and which are active and perform in industrial processes such as pulp bleaching. Therefore, it is an object of the present disclosure to provide a bleaching process with a xylanase enzyme that is able to perform in the said process at high temperature and alkaline pH.
- The appended claims define the scope of protection. Any example and/or technical description of an apparatus, system, product and/or process in the description and/or drawing which is not covered by the claims is presented herein not as an embodiment of the invention but as an example useful for understanding the invention.
- According to a first aspect is provided a bleaching process comprising:
- providing pulp;
- performing a delignification of the pulp by carrying out in the following sequence:
- a) an enzymatic treatment step (X) comprising contacting the pulp with a glycoside hydrolase family GH11 xylanase enzyme at a pH of at least 9.5 and a temperature of at least 85 °C;
- b) an oxidation step (D), wherein a bleaching agent is added;
- c) an alkaline extraction step (E), wherein an alkaline agent is added; and
- d) recovering bleached pulp;
- The inventors have surprisingly found, and show in the examples below, a suitable xylanase enzyme for the present bleaching process can be selected based on the molecular mechanism underlying pulp bleaching performance of the xylanase enzyme, rather than just xylanase enzyme activity or the release of xylan hydrolysis products from pulp. This is rationalized by a pre-bleaching effect of xylanases, being the result mainly of xylan depolymerization, rather than solubilization.
- In an embodiment, GH11 xylanase enzymes that depolymerize xylan without solubilization of xylan are particularly advantageous in a pulp bleaching process, because xylan solubilization may lead to undesirable chemical oxygen demand (COD) increase and pulp yield loss. Therefore, the selection of suitable GH11 xylanase enzyme for pulp bleaching performance should be based on the molecular mechanism underlying the pulp bleaching performance, in addition to and/or instead of the xylanase enzyme activity or the release of xylan hydrolysis products from pulp. When polymers like xylan are depolymerized, the viscosity of a xylan-containing mixture in question is reduced. However, because xylan is only a minor component of pulp, any xylanase induced viscosity reduction in pulp is likely to be small and hardly measurable. It was surprisingly found that xylanase induced viscosity reduction indicating the depolymerization potential of xylanase enzymes, could be measured in xylan-containing mixtures comprising pure or purified xylan, rather than pulp. Furthermore, it was surprisingly found that xylanase induced viscosity reduction is connected to xylanase performance in a pulp bleaching process at high temperature and high pH.
- The bleaching process provides an efficient way to produce delignified and bleached pulp in the presence of the GH11 xylanase enzyme at high temperature and high pH.
- According to a second aspect is provided a pulp composition comprising:
- (a) pulp having a pH of at least 9.5; and
- (b) 0.01 - 200 g of a glycoside hydrolase family GH11 xylanase enzyme protein per 1000 kg of dry matter pulp;
- xylanase activity, and
- an ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 90 °C and pH 10.5 compared to the same mixture without any xylanase enzyme, wherein the xylan-containing mixture comprises 0.07 g/ml or less of xylan and 3.0 µg or less of the GH11 xylanase enzyme protein per gram of said mixture; and wherein the reduction in viscosity takes place within 20 minutes.
- According to a further aspect is provided a bleaching process comprising:
- providing pulp;
- performing a delignification of the pulp by carrying out in the following sequence:
- a) an enzymatic treatment step (X) comprising contacting the pulp with the glycoside hydrolase family GH11 xylanase enzyme at a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C, wherein the xylanase enzyme has a residual xylanase activity of at least 25 % after 20 min of step X;
- b) an oxidation step (D), wherein a bleaching agent is added;
- c) an alkaline extraction step (E), wherein an alkaline agent is added; and
- d) recovering delignified pulp.
- According to a further aspect is provided a pulp composition comprising:
- (a) pulp having a pH of at least 9.5;
- (b) 0.25 - 4 wt-% of a bleaching agent of the total weight of dry matter pulp, the bleaching agent being selected from ClO2, O3, H2O2, and peroxides; and
- (c) 0.01 -200 g of a glycoside hydrolase family GH11 xylanase enzyme protein per 1000 kg of dry matter pulp;
- The present bleaching process comprising the GH11 xylanase enzyme is advantageous in reducing the overall amount of bleaching agent used in the pulp bleaching process. The present bleaching process is advantageous in reducing the amount of ClO2, O3, H2O2 or peroxide consumption in the pulp bleaching process. The present bleaching process is advantageous in achieving higher pulp brightness and/ or higher bleaching product production with the same amount of bleaching agent used in the pulp bleaching process, when compared to a bleaching process without the GH11 xylanase enzyme. The present bleaching process is advantageous in achieving higher pulp brightness and/ or higher bleaching product production with reduced amount of bleaching agent used in the pulp bleaching process, when compared to a bleaching process without the GH11 xylanase enzyme. The present bleaching process is advantageous in reducing the production costs of bleached pulp. The present bleaching process allows more efficient bleaching of the pulp, resulting in more efficient utilization of wood raw material. The present bleaching process is advantageous in integrating the use of the GH11 xylanase enzyme with a high pH- and thermostability to a bleaching process, thereby reducing or avoiding the need to change existing process conditions and/or the setup/hardware commonly used in pulp bleaching. The present bleaching process is advantageous in reducing the corrosion, wear and erosion of the metal pulp bleaching tanks, due to reduced need for lowering pulp pH with acidic agents. The present bleaching process is advantageous in reducing fresh water consumption of the bleaching process, due to reduced need for additional water washes. The present bleaching process is advantageous in reducing the generation of AOX (Adsorbable Organic Halide also known as chloro-organic compounds) which are discharged with the wastewater bleaching effluents. The present bleaching process is advantageous in reducing the amount of energy needed to increase the temperature of pulp after being washed and before the oxygen delignification or before the oxidation step, due to reduced need for lowering pulp temperature for enzyme treatment.
- Different non-binding example aspects and embodiments have been illustrated in the foregoing. The embodiments in the foregoing are used merely to explain selected aspects or steps that may be utilized in different implementations. Some embodiments may be presented only with reference to certain example aspects. It should be appreciated that corresponding embodiments may apply to other example aspects as well.
- Some example embodiments will be described with reference to the accompanying figure, in which:
Fig. 1 shows a flow chart of the process steps of a delignification bleaching process of pulp according to an example embodiment. The process steps X, O, Q inside dashed line boxes indicate optional and/or alternative process steps. -
- SEQ ID NO: 1
- AM24, amino acid sequence of the truncated form of Thermopolyspora flexuosa Xyn11A protein (AM35).The AM24 contains the amino acids D44-L263 of the full-length wild-type AM35
- SEQ ID NO: 2
- Amino acid sequence of the AM24 variant C31-4 comprising the mutations T3C, A23S, S28I, T30C
- SEQ ID NO: 3
- AM35, amino acid sequence of the full length mature Thermopolyspora flexuosa Xyn11A protein
- The invention relates to a bleaching process utilizing a glycoside hydrolase family GH11 xylanase enzyme in a delignification step of the process, said GH11 xylanase enzyme having stability, activity and performance at biologically challenging conditions of high temperature and alkaline pH, resulting in improved bleaching of pulp.
- By the term "bleaching process" is meant a chemical treatment process where the brightness or whiteness of the pulp is increased by removing chemical elements such lignin and chromophoric double bonds that give color to the pulp.
- By the term "delignification" is meant the removal and extraction of lignin contained within pulp. Kappa number can be used as a measure of lignin content in pulp.
- By the term "alkaline extraction step" is meant a bleaching step wherein pH of the pulp is increased to a level where oxidized lignin is extracted from the pulp.
- By the term "glycoside hydrolase" is meant a hydrolase that is capable of hydrolyzing glycosidic bonds between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety.
- The term "glycoside hydrolase family 11" or "GH11" refers to GH11 xylanases according to the definition of the CAZy database, http://www.cazy.org/GH11.html, the GH11 xylanases having a β-jelly roll structure, the GH11 xylanase enzymes thereby differing structurally from other xylanases.
- The term "xylan" refers to matrix polysaccharides or heteropolymers, composed of a repeating β-1,4-linked xylose residue backbone, with various side-chain groups. Xylan polysaccharides can be categorized into classes O-acetylglucuronoxylans (AcGX), O-acetylarabinoxylans (AcAX), Oacetylglucuronoarabinoxylans (AcGAX), and arabinoglucuronoxylans (AGX), based on the substituted side-chain groups. Xylan-containing materials comprise plant-based or plant-originating material.
- As used herein, the term "xylanase" denotes a xylanase enzyme defined according to that known in the art as endo-1,4-β-xylanase, or 4-β-D-xylan xylanohydrolase, known to catalyze the endohydrolysis of (1→4)-β-D-xylosidic linkages in xylans. Xylanases have the alternative names endo-(1→4)-β-xylan 4-xylanohydrolase, endo-1,4-xylanase, xylanase, β-1,4-xylanase, endo-1,4-xylanase, endo-β-1,4-xylanase, endo-1,4-β-D-xylanase, 1,4-β-xylan xylanohydrolase, β-xylanase, β-1,4-xylan xylanohydrolase, endo-1,4-β-xylanase and β-D-xylanase. Xylanases are classified according to the Enzyme Nomenclature as EC 3.2.1.8.
- As used herein, the term "GH11 xylanase enzyme protein" refers to pure GH11 xylanase enzyme protein. According to some embodiments, the GH11 xylanase enzyme protein can be added at an enzymatic treatment step X as one component of a composition, but in such embodiment also, the term GH11 xylanase enzyme protein refers to pure GH11 xylanase enzyme protein as one of the components of the composition. In some embodiments the amount of the GH11 xylanase enzyme protein refers to a dry weight (grams) of the GH11 xylanase enzyme protein, which dry-weight can be determined according to the test procedure described in the examples.
- As used herein, the term "pulp" means water-comprising fibrous material originally obtained from plants. The pulp can originate from wood, fiber crops, bagasse, straw, waste paper or rags, or any combination thereof. Therefore, in the context of this application "pulp" can refer to wood pulp originating from wood material, and/or to non-wood pulp, originating from non-wood material.
- As used herein, the term "wood pulp" means water-comprising fibrous material originating from wood material and produced by digesting hard or softwood chips at temperatures above about 120 °C with a solution of sodium hydroxide and sodium sulfide.
- As used herein, the term "non-wood pulp" means water-comprising fibrous material originating from non-wooden materials, produced by digesting said non-wooden materials, such as grasses, cereal straws, corn stalks, bamboo, kenaf, or bagasse, or any combination thereof.
- As used herein, the term "xylan-containing pulp" means wood or non-wood pulp containing xylan.
- As used herein, the term "hardwood pulp" means wood pulp originating from wood fibers of broadleaved trees such as oak, beech, birch, aspen, eucalyptus and/or poplar.
- As used herein, the term "softwood pulp" means wood pulp originating from wood fibers of needle-bearing trees such as pines, spruce, fir, and/or hemlock.
- As used herein, the term "kraft pulp" means wood pulp produced by the kraft process, also known as the sulfate process, where wood chips are treated with sodium sulfide (Na2S) and sodium hydroxide (NaOH).
- As used herein, the term "thermostable enzyme" or "temperature tolerant enzyme" refers to an enzyme with a good ability to withstand and resist structural changes leading to enzyme inactivation, caused by high temperature such as temperature of 85 °C or higher.
- As used herein, the term "pH stability of an enzyme" or "pH tolerance of an enzyme" describes the enzyme's property to withstand and resist structural changes leading to enzyme inactivation, caused by high pH such as pH of 9.5 or higher, or alternatively, caused by low pH.
- By the term "process water" is meant any water that is used in the pulp bleaching process.
- By the term "process wash water" is meant any water that is used for the purpose of washing pulp in the pulp bleaching process.
- As used herein, the term "viscosity" or "relative viscosity" means the viscosity of the indicated material, such as a xylan-containing mixture, a suspension, or a solution. As used herein, a viscosity reduction of a mixture containing GH11 xylanase enzyme and xylan is an indicator of the xylan depolymerization activity of said GH11 xylanase enzyme. In an embodiment, the lower the viscosity of a xylan-containing mixture is reduced over time, the higher is the xylan depolymerization activity of the GH11 xylanase enzyme. The viscosity is measured with a rolling-ball viscometer.
- As used herein, the term "xylan-containing mixture" refers to a mixture which contains xylan and which mixture can refer to a solution, suspension or a mixture of liquid and solids. In an embodiment, the xylan-containing mixture contains also xylanase enzyme, such as GH11 xylanase enzyme. The xylan-containing mixture is suitable for assessing the xylan-degrading activity of a xylanase enzyme. Therefore, the xylan-containing mixture does not contain any substances, which would distort or falsify the assessment of the xylan degrading activity of a xylanase enzyme. For example, the xylan-containing mixture must be suitable for assessing the effect the GH11 xylanase enzyme has on the viscosity of the xylan-containing mixture.
- As used herein, the term "Adsorbable Organic Halides (AOX)" means a measure of organic halogens chlorine, bromine, and iodine load in a sample, such as water sample.
- As used herein, the term "chemical oxygen demand (COD)" means a measure of the amount of oxygen that can be consumed by reactions in a measured solution. COD indicates the amount of oxygen needed to break down organic matter completely into CO2 in a solution. The COD measurement is also used to determine amount of oxidizable pollutants, and hence, toxicity to biological life, wherein a high COD correlates with a high toxicity of the organic matter.
- As used herein, the term "sequence identity" means the percentage of exact matches of amino acid residues between two optimally aligned sequences over the number of positions where there are residues present in both sequences. When one sequence has a residue with no corresponding residue in the other sequence, the used alignment program allows a gap in the alignment, and that position is not counted in the denominator of the identity calculation.
- As used herein, the term "corresponding positions" or "corresponding amino acid position" means aligning at least two amino acid sequences according to identified regions of similarity or identity as pairwise alignment or as multiple sequence alignment, thereby pairing up the corresponding amino acids.
- As used herein, the term "xylanase activity" refers to the xylan hydrolyzing activity.
- By the term "residual xylanase activity" is meant a xylanase enzyme activity which is not the initial activity of said enzyme, but which has been changed, optionally decreased, due to process conditions the enzyme in question has been exposed to. Therefore, residual xylanase activity refers to the amount, for example the percentage amount, of initial activity left after exposure to specific process conditions.
- The term "functional fragment" means a fragment or portion of the current GH11 xylanase enzyme polypeptide, which retains the same or substantially the same enzymatic function or effect as the entire GH11 xylanase enzyme polypeptide.
- The term "stability" in context of enzyme or xylanase stability, describes the enzyme's property to withstand and/or function in process conditions that are challenging for the activity and functioning of the enzyme in question, such process conditions being, for example, high temperature, pH or radiation, a certain concentration of inorganic salt or an organic solvent, or a specific reaction mixture composition comprising e.g. proteases, stabilizers, builders, surfactants etc. The term "stability" reflects the stability of the xylanase according to the disclosure as a function of time, e.g., how much activity is retained when the xylanase is exposed to process conditions that are challenging for the activity and functioning of the enzyme in question.
- As used herein, Xyn11A denotes a Thermopolyspora flexuosa xylanase from the glycoside hydrolase family 11 (GH11), also named as AM35. As used herein, AM35 denotes the wild-type mature GH11 xylanase, which is the parent polypeptide used for the AM24 polypeptide. The amino acids of the mature AM35 protein correspond to the amino acid sequence of SEQ ID NO: 3.
- As used herein, the AM24 (also called AM24 protein herein) is a truncated form of the xylanase AM35. The AM24 protein comprises the catalytic module (core) and lacks the carbohydrate binding module (CBM) and part of the linker region between core and CBM. The amino acids of the mature polypeptide of AM24 correspond to the amino acids of the sequence SEQ ID NO: 1, comprising the amino acids D1-L220. The "core polypeptide" of AM24 comprises the amino acids D1 - G191 of SEQ ID NO:1, whereas the "inner core polypeptide" of AM24 comprises the amino acids T3 - S180 of SEQ ID NO:1.
- As used herein, the C31-4 refers to a variant of AM24 comprising the substitutions T3C, A23S, S28I, T30C. The amino acids of the mature polypeptide of C31-4 correspond to the amino acids of the sequence SEQ ID NO: 2 comprising the amino acids D1-L220. The "core polypeptide" of C31-4 comprises the amino acids D1 - G191 of SEQ ID NO:2, whereas the "inner core polypeptide" of C31-4 comprises the amino acids C3 - S180 of SEQ ID NO:2.
- As used herein, the term "carbohydrate binding domain" or "CBM" refers to specific domain or module in a polypeptide, which is capable in facilitating the binding of the polypeptide to a carbohydrate.
- As used herein, the term "mature polypeptide" means any polypeptide wherein at least one signal sequence or signal peptide or signal peptide and a putative pro-peptide is cleaved off. For example, the "mature polypeptide" of AM24 comprises the amino acids D1 - L220 of SEQ ID NO:1 and the "mature core polypeptide" of AM24 comprises the amino acids D1 - G191 of SEQ ID NO:1.
- As used herein, a "peptide" and a "polypeptide" are amino acid sequences including a plurality of consecutive polymerized amino acid residues. For purpose of this disclosure, peptides are molecules including up to 20 amino acid residues, and polypeptides include more than 20 amino acid residues. The peptide or polypeptide may include modified amino acid residues, naturally occurring amino acid residues not encoded by a codon, and non-naturally occurring amino acid residues. As used herein, a "protein" may refer to a peptide or a polypeptide of any size. A protein may be an enzyme, a protein, an antibody, a membrane protein, a peptide hormone, regulator, or any other protein.
- As used herein, the term "variant" means a sequence or a fragment of a sequence (nucleotide or amino acid) inserted, substituted or deleted by one or more nucleotides/amino acids, or which is chemically modified. The term variant may in some embodiments also include a variant polypeptide of xylanase, a fusion protein including a variant polypeptide of xylanase, or a recombinant xylanase enzyme.
- The term "xylanase variant" and "variant xylanase" and "variant of xylanase" means any xylanase molecule obtained by site-directed or random mutagenesis, insertion, substitution, deletion, recombination and/or any other protein engineering method, which leads to xylanases that differ in their amino acid sequence from the parent xylanase, the parent xylanase being a wild-type xylanase or a xylanase variant itself. The terms "wild type xylanase", "wild type enzyme", "wild type", or "wt" in accordance with the disclosure, describe a xylanase enzyme with an amino acid sequence found in nature or a fragment thereof. The variant encoding gene can be synthesized or the parent gene be modified using genetic methods, e.g. by site-directed mutagenesis, a technique in which one or more than one mutations are introduced at one or more defined sites in a polynucleotide encoding the parent polypeptide.
- As used herein, the term "disulfide bridge" refers to a bond formed between the sulfur atoms of cysteine residues in a polypeptide or a protein. Disulfide bridges can be naturally occurring, or non-naturally occurring, and, for example, introduced by way of amino acid substitution(s).
- The term "catalytic domain" or "catalytic module" or "core" or "catalytic core domain" denotes a domain of an enzyme, which may or may not have been modified or altered, but which retains at least part of its original activity.
- By the term "linker" or "spacer" is meant a polypeptide comprising at least two amino acids which may be present between the domains of a multidomain protein, for example an enzyme comprising a catalytic domain and a binding domain such as a carbohydrate binding module (CBM), or any other enzyme hybrid, or between two proteins or polypeptides produced as a fusion polypeptide, for example a fusion protein comprising two core enzymes. For example, the fusion protein of a catalytic domain with a CBM is provided by fusing a DNA sequence encoding the catalytic domain, a DNA sequence encoding the linker and a DNA sequence encoding the CBM sequentially into one open reading frame and expressing this construct.
- As used herein, the term "dry matter" or "dry matter pulp" or "O.D. pulp" refers to pulp dried with the oven-drying method, wherein the dry matter pulp is moisture-free, i.e., free of water. The dry matter content of oven-dried pulp can be determined according to ISO 638:2008.
- As used herein, "amino acid substitution" means an amino acid residue replacement with an amino acid residue that is different than the original amino acid in that specific replacement position. The term "amino acid substitution" can refer to both, conservative amino acid substitutions and non-conservative amino acid substitutions, which means the amino acid residue is replaced with an amino acid residue having a similar side chain (conservative), or a different side chain (non-conservative), as the original amino acid residue in that place. Substitutions are described using of the following nomenclature: amino acid residue in the protein scaffold; position; substituted amino acid residue(s). According to this nomenclature the substitution of, for instance, a single residue of alanine to serine residue at position 23 is indicated as Ala23Ser or A23S.
- As used herein, the term "comprising" includes the broader meanings of "including", and "containing", as well as the narrower expressions "consisting of" and "consisting only of". The words "comprise", "include", and "contain" are each used as open-ended expressions with no intended exclusivity.
- In an embodiment, material originating from wood material or non-wood material is bleached in the bleaching process. In an embodiment, prior to the bleaching process, the wood or non-wood material is digested in a digester, for obtaining pulp. In an embodiment, the pulp is treated with chemicals to dissolve lignin in the pulp.
- In an embodiment, the pulp is hardwood pulp or softwood pulp, or mixture thereof. In an embodiment, the pulp is non-wood pulp. In an embodiment, the pulp is xylan-containing pulp. In an embodiment, the pulp is kraft pulp cooked in alkaline liquor. In an embodiment, the bleaching process comprises multiple steps and one or more water washes in between the steps, or alternatively, each or some of the stages comprises a water wash as a final step of the stage.
- In an embodiment, the bleaching process comprises providing pulp and performing a delignification of the pulp by carrying out in the following sequence: a) an enzymatic treatment step (X) comprising contacting the pulp with a glycoside hydrolase family GH11 xylanase enzyme at a pH of at least 9.5 and a temperature of at least 85 °C; b) an oxidation step (D), wherein a bleaching agent is added; c) an alkaline extraction step (E), wherein an alkaline agent is added; and d) recovering bleached pulp. In an embodiment, the GH11 xylanase enzyme used in the bleaching process, has an ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 90 °C and pH 10.5, compared to the same mixture without any xylanase enzyme.
- In an embodiment, the GH11 xylanase enzyme is a glycoside hydrolase family 11 xylanase enzyme.
- In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 25 %, preferably at least 30 %, more preferably at least 40 % and most preferably at least 50 % reduction in viscosity of the xylan-containing mixture, compared to the same mixture without any xylanase enzyme.
- In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 17 %, preferably at least 20 %, more preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, even more preferably at least 50 %, most preferably at least 60 % reduction in viscosity of a xylan-containing mixture at 85 - 100 °C and at pH 9.5 - 11.5, compared to the same mixture without any xylanase enzyme.
- In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 10 %, preferably at least 20 %, more preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, even more preferably at least 60 %, most preferably at least 70 % reduction in viscosity of a xylan-containing mixture at 85 - 90 °C and at pH 8 - 11, compared to the same mixture without any xylanase enzyme. In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 50 %, preferably at least 55 %, more preferably at least 60 %, more preferably at least 65 %, even more preferably at least 70 %, most preferably at least 75 %, reduction in viscosity of a xylan-containing mixture at 85 - 90 °C and at pH 8 - 11, compared to the same mixture without any xylanase enzyme.
- In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 10 %, preferably at least 20 %, more preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, even more preferably at least 50 %, most preferably at least 60 %, reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10 - 11, compared to the same mixture without any xylanase enzyme. In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 50 %, preferably at least 55 %, more preferably at least 60 %, more preferably at least 65 %, even more preferably at least 70 %, most preferably at least 75 %, reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10 - 11, compared to the same mixture without any xylanase enzyme.
- In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 20 %, preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, even more preferably at least 60 %, most preferably at least 69 % reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10.5, compared to the same mixture without any xylanase enzyme.
- In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 25 % reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10.5, compared to the same mixture without any xylanase enzyme.
- In an embodiment, the GH11 xylanase enzyme used in the step X has the ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 85 - 100 °C and pH 9.5 - 11.5, compared to the same mixture without any xylanase enzyme. In an embodiment, the GH11 xylanase enzyme used in the step X has the ability to cause at least 10 %, preferably at least 20 %, more preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, even more preferably at least 60 %, most preferably at least 70 % reduction in viscosity of a xylan-containing mixture at 85 -100 °C and at pH 9.5 -11.5, compared to the same mixture without any xylanase enzyme. In an embodiment, the ability of the GH11 xylanase enzyme to cause a strong reduction in viscosity of a xylan-containing mixture is an indicator of the enzyme's xylan depolymerisation activity. Therefore, a strong reduction in viscosity of a xylan-containing mixture indicates the GH11 xylanase enzyme used has a high xylan depolymerisation activity. In an embodiment, the stronger the viscosity reduction of the xylan-containing mixture in the presence of the GH11 xylanase enzyme, the higher is the xylan depolymerisation activity of the GH11 xylanase enzyme. In an embodiment, the xylan depolymerisation activity of the GH11 xylanase is an indicator of the thermostability and pH stability of the said enzyme. In an embodiment, the xylan depolymerisation activity of the GH11 xylanase at 90°C and pH 10.5 is an indicator of the thermostability and pH stability of the said enzyme. A high xylan depolymerisation activity indicates the GH11 xylanase in question is suitable for pulp bleaching with high pH and temperature, such as pH 9 - 12 and a temperature of 85 - 100 °C, preferably pH 9.5 - 11.5 and a temperature of 85 - 100 °C.
- In an embodiment, the xylan depolymerization activity of the GH11 xylanase enzyme is tested in a xylan-containing mixture which is not wood pulp.
- In an embodiment, the xylan-containing mixture comprises: not more than 0.07 g xylan per ml of said mixture, and not more than 3.0 µg of the GH11 xylanase enzyme protein per gram of said mixture; and wherein the reduction in viscosity takes place within 20 minutes, preferably within 10 minutes, more preferably within 5 minutes and most preferably within 2 minutes. In an embodiment, the xylan-containing mixture comprises: 0.07 g/ml or less of xylan, and 3.0 µg or less of the GH11 xylanase enzyme protein per gram of said mixture. In an embodiment, the reduction in viscosity of the xylan-containing mixture takes place within 20 minutes preferably within 10 minutes, more preferably within 5 minutes and most preferably within 2 minutes.
- In an embodiment, the xylan-containing mixture comprises ≤ 0.07 g/ml, ≤ 0.06 g/ml, ≤ 0.05 g/ml, ≤ 0.04 g/ml, ≤ 0.03 g/ml, ≤ 0.02 g/ml, ≤ 0.01 g/ml or less of xylan. In an embodiment, the concentration of GH11 xylanase enzyme in the xylan-containing mixture is ≤ 3.0, ≤ 2.9, ≤ 2.5, ≤ 2.0, ≤ 1.9, ≤ 1.5, ≤ 1.0, ≤ 0.5, ≤ 0.3, or ≤ 0.1 µg xylanase enzyme protein per gram of said mixture. In an embodiment, the viscosity of the xylan-containing mixture is reduced with the GH11 xylanase enzyme within 20 min, 15 min, 10 min, 5 min, 2 min or less.
- In an embodiment, the step X comprises contacting the pulp with the GH11 xylanase enzyme at a pH 9.5 - 11.5 and a temperature of 85 - 100 °C.
- In an embodiment, the step X comprises contacting the pulp with the GH11 xylanase enzyme at a pH of at least 9.5 and a temperature of at least 85 °C. In an embodiment, the step X comprises a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C. In an embodiment, the pH of the pulp during the step X is 9.5 - 11.5. In an embodiment, the temperature of the pulp during the step X is 85 - 100 °C.
- In an embodiment, the GH11 xylanase enzyme is added to the pulp with a pH selected from ≥ 9.5, ≥ 10, ≥ 10.5, ≥ 11, and 11.5. In an embodiment, the GH11 xylanase enzyme is added to the pulp with a temperature selected from ≥ 85 °C, ≥ 90 °C, ≥ 95 °C, and 100 °C.
- In an embodiment, lowering of alkaline pH of the pulp and/or lowering of process temperature prior to addition of the GH11 xylanase enzyme is/are omitted. In an embodiment, an alkaline pH of the pulp is not lowered with acid and/or acid washing step(s) and/or the temperature of the pulp is not reduced with water prior to addition of the GH11 xylanase enzyme, as the GH11 xylanase enzyme tolerates the high delignification pH and temperature of the bleaching process. In an embodiment, since lowering of process temperature with excess water prior to addition of the GH11 xylanase enzyme is not necessary, the water consumption of the bleaching process is reduced. In an embodiment, as lowering of process pH with acid prior to addition of the GH11 xylanase enzyme is not necessary, acid consumption of the bleaching process and the bleaching process hardware wear is reduced.
- In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 90 °C and at pH 10.5, compared to the same mixture without any xylanase enzyme, wherein the xylan-containing mixture comprises: ≤ 0.07 g/ml of xylan, and ≤ 3.0 µg of the GH11 xylanase enzyme protein per gram of said mixture; and wherein the reduction in viscosity takes place within 20 minutes.
- In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 20 %, preferably at least 25 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, even more preferably at least 60 %, most preferably at least 65 % reduction in viscosity of said xylan-containing mixture within 20 minutes at a pH of 10.5 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme protein concentration is ≤ 3.0 µg per g of xylan-containing mixture.
- In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 10 % reduction in viscosity of xylan-containing mixture within 20 minutes at a pH of 11 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme concentration is 1.9 µg xylanase protein per g of xylan-containing mixture. In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 53 % reduction in viscosity of xylan-containing mixture within 20 minutes at a pH of 11 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme concentration is 1.9 µg xylanase protein per g of xylan-containing mixture. In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 17 % reduction in viscosity of xylan-containing mixture within 20 minutes at pH of 10 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme concentration is 2.9 µg xylanase protein per g of xylan-containing mixture. In an embodiment, the GH11 xylanase enzyme has an ability to cause at least 58 % reduction in viscosity of xylan-containing mixture within 20 minutes at pH of 10 and at a temperature of 90°C, when compared to the xylan-containing mixture without any xylanase enzyme, wherein the GH11 xylanase enzyme concentration is 1.9 µg xylanase protein per g of xylan-containing mixture.
- In an embodiment, the GH11 xylanase enzyme has a residual xylanase activity of at least 25 %, preferably at least 50 % and more preferably at least 75% after 10 min, preferably after 20 min, more preferably after 30 min of the step X. In an embodiment, the GH11 xylanase enzyme has a residual xylanase activity of at least 25 %, preferably at least 50 %, more preferably at least 75 % after 20 min of the step X, wherein the step X comprises a pH 9.5 - 11.5 and a temperature of 85 - 100 °C.
- In an embodiment, the GH11 xylanase enzyme has a residual xylanase activity of at least 25 % after 30 min, preferably after 40 min, more preferably after 50 min of the step X, wherein the step X comprises a pH 9.5 - 11.5 and a temperature of 85 - 100 °C.
- In an embodiment, the xylanase enzyme retains at least 25 % of its xylanase activity after 20 min at 85°C and at pH 9.5.
- In an embodiment, the xylanase enzyme retains at least 25 % of its xylanase activity after 20 min at 100°C and at pH 11.5.
- In an embodiment, the GH11 xylanase enzyme has a residual xylanase activity of at least 75 %, preferably at least 80 %, more preferably at least 85 % after at least 30 min at pH 10.9 and a temperature of 85 °C. In an embodiment, the GH11 xylanase enzyme in a hardwood pulp bleaching process water has a residual xylanase activity of at least 75 %, preferably at least 80 %, more preferably at least 85 % after at least 30 min at pH 10.9 and a temperature of 85 °C.
- In an embodiment, the xylanase enzyme has a residual xylanase activity of at least 75 %, preferably at least 80 %, more preferably at least 85 % after at least 30 min at pH 10.5 and a temperature of 85 °C. In an embodiment, the GH11 xylanase enzyme in a softwood pulp bleaching process water has a residual xylanase activity of at least 75 %, preferably at least 80 %, more preferably at least 85 % after at least 30 min at pH 10.5 and a temperature of 85 °C.
- In an embodiment, the bleaching process comprises: providing pulp; performing a delignification of the pulp, by carrying out in the following sequence: (a) an enzymatic treatment step (X) comprising contacting the pulp with the glycoside hydrolase family GH11 xylanase enzyme at a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C, wherein the xylanase enzyme has a residual xylanase activity of at least 25 % after 20 min of step X; (b) an oxidation step (D), wherein a bleaching agent is added; (c) an alkaline extraction step (E), wherein an alkaline agent is added; and (d) recovering delignified pulp.
- In an embodiment, the pulp is provided to the delignification of the bleaching process from a digester.
- In an embodiment, at least 0.01 g, preferably at least 0.1 g, more preferably at least 0.2 g, most preferably at least 0.5 g of the GH11 xylanase enzyme protein is added per 1000 kg of dry matter pulp at the step X.
- In an embodiment, the GH11 xylanase enzyme is added to the step X at a concentration of 0.01 - 200 g, or 0.1 - 20 g, or 0.2 - 10 g, or 0.5 - 5 g of the GH11 xylanase enzyme protein per 1000 kg of dry matter pulp. In an embodiment, the concentration of the GH11 xylanase enzyme depends on the type of pulp used.
- In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the glycoside hydrolase family GH11 xylanase enzyme and at least one further enzyme selected from the group consisting of protease, amylase, cellulase, β-glucosidase, lipase, xylanase, mannanase, cutinase, esterase, α-glucuronidase, phytase, nuclease, pectinase, pectinolytic enzyme, pectate lyase, carbohydrase, arabinase, galactanase, xanthanase, xyloglucanase, polysaccharide monooxygenase, laccase, peroxidase and oxidase with or without a mediator, or a combination thereof.
- In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a cellulase enzyme. In an embodiment, the enzymatic treatment step X comprises contacting the pulp with the GH11 xylanase enzyme and a mannanase enzyme. In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a peroxidase enzyme. In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a lignin peroxidase enzyme (EC 1.11.1.14). In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a manganese peroxidase enzyme (EC 1.11.1.13). In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a versatile peroxidase enzyme (EC 1.11.1.16). In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a dye-decolorizing peroxidase enzyme (EC 1.11.1.19). In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a haem peroxidase enzyme. In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a copper-based laccase enzyme (EC 1.10.3.2).
- In an embodiment, the bleaching process comprises contacting the pulp with a surfactant, surface-active agent, anti-foaming agent, defoamer, emulsifier, dispersant and/or detergent. In an embodiment, the enzymatic treatment step (X) comprises contacting the pulp with the GH11 xylanase enzyme and a surfactant, surface-active agent, anti-foaming agent, defoamer, emulsifier, dispersant and/or detergent.
- In an embodiment, the enzymatic treatment step (X) comprises contacting pulp with an enzyme composition which comprises one or more enzymatic activities, possibly isolated and purified, from one or more species of a microorganism. In an embodiment, the enzymes of the enzyme composition may originate from different species, preferably fungal or bacterial species, or they are present in a fermentation product of a one microorganism which acts as a host cell for enzyme production, such as in the production of the GH11 xylanase enzyme, when the microorganism simultaneously produces other enzymes in addition to the GH11 xylanase enzyme.
- In an embodiment, the enzymatic treatment step (X) comprises contacting pulp with an enzyme composition comprising the GH11 xylanase enzyme protein.
- In an embodiment, the pulp is an aqueous mixture, comprising at least 0.5 - 35 wt-% of pulp fibers, wherein the pulp fibers are wood fibers and/or non-wood fibers. In an embodiment, the pulp fibers contain xylan, the pulp therefore being xylan-containing pulp.
- In an embodiment, the delignification is done in the presence of the GH11 xylanase enzyme, the GH11 xylanase enzyme having high pH and thermostability.
- In an embodiment, the contacting of the pulp with the GH11 xylanase enzyme in the step X means the GH11 xylanase enzyme is contacted with the xylan comprised by the pulp.
- In an embodiment, the delignification further comprises an oxygen-delignification step (O) before the oxidation step D, wherein oxygen is added at the step O; and wherein the step X is before or after the step O.
- In an embodiment, oxygen is added as O2 gas in the oxygen-delignification step, wherein the step is called O2 step.
- In an embodiment, the duration of the enzymatic treatment step X is at least 2 min, at least 5 min, at least 10 min, at least 15 min, at least 20 min, at least 30 min, at least 1 h, at least 1,5 h, at least 2 h, at least 2,5 h, or at least 3 h. In an embodiment, the duration of the enzymatic treatment step X is 2 min - 3 h, 5 min - 2 h, 15 - 60 min, or 20 - 30 min. In an embodiment, the temperature of the step X is at least 80 °C, at least 85 °C, at least 90 °C, at least 95 °C, or at least 100 °C. In an embodiment, the pH of the pulp during the step X is at least 8.5, at least 9.0, at least 9.5, at least 10, at least 10.5, at least 11, at least 11.5 or at least 12.
- In an embodiment, the duration of the step O is at least 0.5 h, at least 1h, at least 1.5 h, at least 2 h, at least 2.5 h, or at least 3 h. In an embodiment, the temperature of the step O is at least 75 °C, at least 80 °C, at least 85 °C, at least 90 °C, at least 95 °C, at least 105 °C, at least 110 °C, at least 115 °C, at least 120 °C, at least 125 °C, or at least 130 °C. In an embodiment, the pH of the pulp during the step O is at least 9.5, at least 10, at least 10.5, at least 11, at least 11.5, or at least 12. In an embodiment, the pH and the temperature of the pulp can change during the step O.
- In an embodiment, the pH of the pulp during the step O is 10 - 12 and/or the temperature is 75 - 130 °C.
- In an embodiment, the xylanase enzyme is added to the pulp before the step O as its own enzymatic treatment step X. In an embodiment, the xylanase enzyme is added to the pulp before the step O, and the xylanase enzyme retains at least 25 % residual xylanase activity during at least 20 min of the enzymatic treatment step X comprising a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C. The step O releases high amounts of lignin from the pulp. Therefore, in the embodiments wherein the bleaching process comprises the step X prior to step O, washing the pulp between the step X and the step O is not necessary. In an embodiment, wherein the GH11 xylanase enzyme is added to the pulp before the step O, the GH11 xylanase enzyme in the pulp retains some of its activity in the step O.
- In an embodiment, the xylanase enzyme is added to the pulp after the step O and before the step D as its own enzymatic treatment step X. In an embodiment, the xylanase enzyme is added to the pulp after the step O, and the xylanase enzyme retains at least 25 % residual xylanase activity during at least 20 min of the enzymatic treatment step X comprising a pH of 9.5 - 11.5 and a temperature of 85 - 100 °C. In an embodiment, the GH11 xylanase enzyme can be added at any stage prior to step D, as long as the step X is done in the presence of the GH11 xylanase enzyme having a residual xylanase activity of at least 25 % after at least 20 min at pH of 9.5 - 11.5 and temperature of 85 - 100 °C. In an embodiment, the GH11 xylanase enzyme has activity at any pH between 5.6 - 11.5 and/or at any temperature between 55 - 100 °C.
- In an embodiment, adding the GH11 xylanase enzyme to the pulp before or after the step O, and before the step D, allows performing the step X in a pre-existing storage tank or a storage tower of a pulp processing facility, without the need to build separate processing containers/tanks when integrating the enzymatic treatment step X into a bleaching process of pulp, which process did not contain an enzymatic treatment step X previously.
- In an embodiment, each step of the delignification of the bleaching process takes place in a separate tank, as indicated in the
Fig. 1 . In an embodiment, the optional oxygen-delignification step (O) is performed in a separate tank O. In an embodiment, the enzymatic treatment step (X) can be performed in a separate storage tank S1 and/or S2, before and/or after the step O, respectively. In an embodiment, performing the step X in a separate storage tank S1 and/or S2 allows an adequate retention time for the enzymatic treatment of the pulp. However, depending on the process, the presence of storage tank S1 and/or S2 may not be necessary, as the enzymatic treatment step X can be performed in another process tank preceding in the bleaching process sequence the tank D, wherein the oxidation step D is performed. - In an embodiment, the oxidation step D is performed in a tank D (
Fig. 1 ). In an embodiment, wherein the bleaching process does not comprise the step O, the pulp is directed from the digester (not shown) directly, or via other tanks, such as storage tanks S1 and/or S2, to the oxidation step in the tank D. In an embodiment, wherein the bleaching process comprises the step O, the oxygen-treated pulp is directed from the tank O directly, or via other tanks, such as storage tank S2, to the tank D. Preferably, the pulp is washed in between the tanks O and D, to remove dissolved lignin. In an embodiment, wherein the bleaching process includes a process sequence comprising the steps O, X, D, and a water washing step of the pulp is performed after the step X, at least part of the wash water comprising the GH11 xylanase enzyme is recycled back to the step O. In an embodiment, wherein the bleaching process includes a process sequence comprising the steps O, X, D, and a water washing step of the pulp is performed between the steps O and X, washing the pulp between the steps X and D is optional. However, in this case also if a water washing step of the pulp is performed after the step X, at least part of the wash water comprising the GH11 xylanase enzyme is recycled back to the step O. In an embodiment, the GH11 xylanase enzyme in the pulp retains some of its activity in the step D, if no washing step is performed between the steps X and D. - In an embodiment, the bleaching agent at the oxidation step D comprises an oxygen-containing oxidizing agent, preferably the bleaching agent is selected from a group consisting of ClO2, O3, H2O2, and peroxides. Examples for non-oxygen-containing oxidizing agents are Cl2 and other halogens. In an embodiment, the bleaching agent is a chemical compound comprising the element oxygen. In an embodiment, the bleaching agent is ClO2. In an embodiment, the bleaching agent is H2O2. In an embodiment, the bleaching agent is an organic peroxide. In an embodiment, the bleaching agent is an inorganic peroxide. In an embodiment, the bleaching agent is O3. In an embodiment, the bleaching agent is ClO2 and the oxidation step is called step Do. In an embodiment, the pulp is directed into the tank D for the step D and the bleaching agent is added in the tank D.
- In an embodiment, both the GH11 xylanase enzyme and the bleaching agent participate in bleaching the pulp during the bleaching process, and therefore the amount of bleaching agent required in the bleaching process is reduced when compared to a bleaching process without any xylanase enzyme. In an embodiment, the pulp comprises the GH11 xylanase enzyme with residual activity in the step D, both the GH11 xylanase enzyme and the bleaching agent participating in bleaching the pulp simultaneously. In an embodiment, the pulp comprises the GH11 xylanase enzyme with residual activity in the step D, and the bleaching agent in the step D is preferably H2O2. In another embodiment, the pulp no longer comprises the GH11 xylanase enzyme at the step D, as the enzyme has been removed in a washing step prior to the step D. In such embodiment also, the required amount of bleaching agent in the oxidation step is reduced when compared to a bleaching process without any xylanase enzyme, as the pulp entering the step D is already bleached to some degree in the enzymatic treatment step X. In an embodiment, at least 5 %, preferably at least 7,5 %, more preferably at least 10 % less of the bleaching agent is used than in a corresponding process without the GH11 xylanase enzyme, for achieving a specific pulp brightness. In an embodiment, the reduction of the amount of bleaching agent leads to reduction in the amount of Adsorbable Organic Halides (AOX) in a water effluent of the bleaching process and reduced need for effluent water treatment afterwards.
- In an embodiment, the GH11 xylanase enzyme used in the bleaching process is highly tolerant to high pH and temperature. In an embodiment, the use of temperature and pH tolerant xylanase enzyme in the bleaching process results in higher pulp brightness when compared to a bleaching process without a xylanase enzyme, or when compared to a process comprising less temperature and pH tolerant xylanase enzyme. On the other hand, the use of temperature and pH tolerant xylanase enzyme in the bleaching process results in a reduced need of bleaching agent, when a specific pulp brightness is desired.
- In an embodiment, the bleaching agent used is H2O2, a metal chelation step (Q) for removal of metals is performed prior to the oxidation step D, and the GH11 xylanase enzyme is added to the pulp before, during or after the chelation step Q. In an embodiment, the step Q comprises washing the pulp with a chelating agent, such as EDTA or DTPA, for removing redox-active metal ions from the pulp. In an embodiment, the duration of the step Q is the same as the duration of the step X.
- In an embodiment, the step Q takes place in a separate metal chelation tank Q, prior to the step D in the bleaching process sequence (
Fig. 1 ). The purpose of the step Q is to remove metals from the pulp which reduce the bleaching activity of H2O2, such metals being, for example, copper, manganese and iron. In an embodiment, the enzymatic treatment step X of the pulp is performed in the same tank Q as the metal chelation step. In an embodiment, the enzymatic treatment step X of the pulp is performed in the same tank Q as the metal chelation step, before, after or during the metal chelation step. Alternatively, the step X is performed in another tank prior to and/or after the step Q. In an embodiment, the step Q takes place after the oxygen-delignification is performed to the pulp in the tank O. In an embodiment, the pulp is directed from metal chelation in the tank Q directly, or via other tanks to the oxidation step in the tank D. In an embodiment, the pulp is directed from the tank Q to a storage tank (not shown), wherein the enzymatic treatment step X is performed, after which the pulp is directed to the oxidation step in the tank D. Preferably, the pulp is washed in between the steps Q and D, to remove the dissolved metals from the pulp prior to the oxidation step. - In an embodiment the GH11 xylanase enzyme can be added to the pulp before, during or after the step Q. In an embodiment, wherein the xylanase enzyme is added to the pulp before or during the step Q, and the process comprises a water washing step of the pulp between the step Q and the oxidation step in the tank D. In this case, at least part of the wash water comprising the GH11 xylanase enzyme with residual activity can be recycled back to the metal chelation in the tank Q, preferably, at least part of the said wash water is recycled back to a pulp washer upstream from the tank Q. In an embodiment, wherein the pulp is washed with water between the steps Q and D, the GH11 xylanase enzyme can be first added to the pulp in the tank D or in a separate storage tank (not shown) after the washing step, before the addition of the bleaching agent H2O2. In such embodiment, the GH11 xylanase enzyme in the pulp can retain some of its activity in the step D.
- In an embodiment, the duration of the delignification oxidation step in tank D is at least 0.5 h, at least 1h, at least 1.5 h, at least 2 h, at least 2.5 h, or at least 3 h. In an embodiment, the temperature of the delignification oxidation step is at least 50 °C, at least 60 °C, at least 70 °C, at least 80 °C, at least 90 °C, or at least 100 °C. In an embodiment, the pH of the pulp during the delignification oxidation step is 12 or less, 11 or less, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. In an embodiment, the bleaching agent added in the step D reduces the pH of the pulp after oxidation.
- In an embodiment, after the step D, the pulp is directed to the alkaline extraction step E in the tank E (
Fig. 1 ). In an embodiment, the bleaching process also includes a water washing step of the pulp between the oxidation step in the tank D and the alkaline extraction step in the tank E. In such embodiments, the wash water optionally comprising the GH11 xylanase enzyme is recycled back to a water washing step before the step D. In an embodiment, wherein the bleaching agent at the step D is H2O2, the xylanase enzyme in the wash water being recycled back into a water washing step still has residual activity and is able to contribute to xylan degradation in the tank D. - In an embodiment, the alkaline agent is added into the alkaline extraction step E in the tank E. In an embodiment, the alkaline agent of the alkaline extraction step E is selected from NaOH, MgO, or combinations thereof. In an embodiment, the alkaline agent is a mixture of NaOH and H2O2, or a mixture of NaOH and O2 or a mixture of NaOH+O2+H2O2.
- In an embodiment, the reduction in the amount of needed ClO2 as a bleaching agent results into reduced amount of NaOH as an alkaline agent required in the step E. In an embodiment, the reduction in the amount of NaOH as an alkaline agent results into reduction in the chemical oxygen demand (COD) measure of the bleaching process effluent water.
- In an embodiment, the GH11 xylanase enzyme has a higher activity in a delignification process water than in normal tap water, when the process conditions including temperature and pH are the same. In an embodiment, the process water at the delignification stage induces the enzyme stability.
- In an embodiment, the duration of the delignification alkaline extraction step E is at least 0.5 h, at least 1h, at least 1.5 h, at least 2 h, at least 2.5 h, or at least 3 h. In an embodiment, the temperature of the step E is at least 70 °C, at least 80 °C, at least 90 °C, or at least 100 °C. In an embodiment, the pH of the pulp during the step E is at least 8, at least 9, at least 9.5, at least 10, at least 10.5, or at least 11. In an embodiment, the alkaline agent increases the pH of the pulp, the pH of the pulp being alkaline at the beginning of the alkaline extraction step, and less alkaline at the end of the alkaline extraction step.
- In an embodiment, at least 1 unit, preferably at least 2 units, more preferably at least 2.5 units higher final brightness of the pulp can be achieved with the current bleaching process, than with a corresponding process without the GH11 xylanase enzyme.
- In an embodiment, the delignification of the bleaching process is followed by a brightening section of the delignified pulp, which can also comprise several process steps. The brightening section can comprise at least one or more brightening steps (Db, P), wherein a bleaching agent is added, and/or one or more brightening alkaline extraction steps (Eb), wherein an alkaline agent is added. In an embodiment, the main purpose of the brightening section is not to remove remaining lignin from the pulp but to decolorize remaining lignin, thereby obtaining a higher final brightness.
- In an embodiment, the glycoside hydrolase family GH11 xylanase enzyme used in the bleaching process according to the invention can be of various origin. In an embodiment, the xylanase enzyme used in the bleaching process according to the invention, is a wild type xylanase enzyme. In an alternative embodiment, the xylanase enzyme used in the bleaching process according to the invention, is a modified xylanase enzyme, and/or a variant of a wild type xylanase enzyme.
- In an embodiment, the GH11 xylanase enzyme originates from a thermophilic bacteria. In an embodiment, the GH11 xylanase enzyme originates from bacteria, preferably from Actinobacteria, more preferably from Streptosporangiales, more preferably from Streptosporangiaceae, even more preferably from Thermopolyspora species, most preferably from Thermopolyspora flexuosa. In an embodiment, the xylanase enzyme originates from the group of terrabacteria. In an embodiment, the xylanase enzyme originates from a phylum of Actinobacteria. In an embodiment, the xylanase enzyme originates from class of Actinomycetia. In an embodiment, the xylanase enzyme originates from the order of Streptosporangiales. In an embodiment, the xylanase enzyme originates from the family of Streptosporangiaceae. In an embodiment, the xylanase enzyme originates from the genus of Thermopolyspora.
- In an embodiment, the GH11 xylanase enzyme originates from Thermopolyspora flexuosa. Thermopolyspora flexuosa is meant synonymous to Nonomuraea flexuosa, Nonomuria flexuosa, Nocardia flexuosa, Microtetraspora flexuosa, Acetomadura flexuosa and/or Actinomadura flexuosa.
- In an embodiment, the glycoside hydrolase family GH11 xylanase enzyme used in the bleaching process comprises a catalytic core domain and a carbohydrate binding module (CBM), linked together by a linker. In an embodiment, the glycoside hydrolase family GH11 xylanase enzyme used in the bleaching process is a truncated enzyme, comprising a catalytic core domain and a linker domain, or a catalytic core domain and part of a linker domain, whereas a CBM is absent. In yet another embodiment, the glycoside hydrolase family GH11 xylanase enzyme used in the bleaching process comprises only a catalytic core domain, whereas a linker domain and a CBM are absent. In an embodiment, the GH11 xylanase enzyme used in the bleaching process comprises a mature catalytic core domain.
- In an embodiment, the GH11 xylanase enzyme is a polypeptide, wherein the polypeptide, or a functional fragment of the polypeptide, has a molecular mass of 15 - 100 kDa, preferably 18 - 70 kDa, more preferably 19 - 40 kDa, even more preferably 20 - 33 kDa. In an embodiment, the GH11 xylanase enzyme has a molecular mass of 19 - 40 kDa, preferably 20 - 30 kDa, more preferably 23 - 25 kDa, most preferably 24 kDa, calculated from its amino acid sequence without glycosylation. In an embodiment, the GH11 xylanase enzyme has a β-jelly roll structure.
- In an embodiment, the GH11 xylanase enzyme is a polypeptide, wherein the polypeptide or a functional fragment of the polypeptide has a molecular mass of 31 kDa. In an embodiment, the GH11 xylanase enzyme is a polypeptide, wherein the polypeptide or a functional fragment of the polypeptide has a molecular mass of 27 kDa. In an embodiment, the GH11 xylanase enzyme is a polypeptide, wherein the polypeptide or a functional fragment of the polypeptide has a molecular mass of 24 kDa. The molecular mass of the GH11 xylanase enzyme polypeptide or a functional fragment of the polypeptide can be determined by SDS-PAGE. In an embodiment, the molecular mass of the GH11 xylanase enzyme polypeptide or a functional fragment of the polypeptide is calculated from its amino acid sequence without glycosylation. In an embodiment, the GH11 xylanase enzyme polypeptide or a functional fragment of the polypeptide has a molecular mass of 24 kDa, calculated from its amino acid sequence without glycosylation. In an embodiment, the GH11 xylanase enzyme lacks xylosidase and cellulase activity.
- In an embodiment, the GH11 xylanase enzyme is a variant polypeptide. In an embodiment, the GH11 xylanase enzyme is a wild type polypeptide.
- In an embodiment, the GH11 xylanase enzyme has at least one, or at least two disulfide bridges between two cysteine residues in its amino acid sequence. In an embodiment, the at least one disulfide bridge stabilizes the GH11 xylanase enzyme, thereby increasing the pH stability and thermostability of the GH11 xylanase enzyme.
- In an embodiment the GH11 xylanase enzyme is a polypeptide comprising residues 3C and 30C, the positions of these residues corresponding to the positions 3 and 30 of the SEQ ID NO: 2, and a disulfide bridge being formed between the residues 3C and 30C. In an embodiment the GH11 xylanase enzyme is polypeptide comprising at least one disulfide bridge between two cysteine residues in the 1 - 191 amino acid region of the polypeptide, the position of at least one of the two cysteine residues being different from the positions corresponding to positions 3 and 30 of the SEQ ID NO: 2. In an embodiment the GH11 xylanase enzyme is polypeptide comprising at least one disulfide bridge between cysteine residues in the 1 - 30 amino acid region of the polypeptide, the positions of the amino acid region corresponding to positions of the SEQ ID NO: 2.
- In an embodiment, the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having amino acids corresponding to the amino acids 3 - 180 of SEQ ID NO: 2, or functional fragments thereof; the GH11 xylanase enzyme having at least one disulfide bridge between two cysteine residues of the polypeptide. In an embodiment, the GH11 xylanase enzyme is polypeptide comprising an amino acid sequence having amino acids corresponding to the amino acids 1 - 191 of SEQ ID NO: 2; or functional fragments thereof, the GH11 xylanase enzyme having at least one disulfide bridge between two cysteine residues of the polypeptide. In an embodiment, the at least one disulfide bridge stabilizes the GH11 xylanase enzyme, thereby increasing the pH stability and thermostability of the GH11 xylanase enzyme compared to a GH11 xylanase enzyme without a disulfide bridge. In an embodiment, the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having amino acids corresponding to the amino acids 1 - 191 of SEQ ID NO: 1; the GH11 xylanase enzyme having at least one disulfide bridge between two cysteine residues of the polypeptide, and one or two amino acid substitution(s) at a position/positions corresponding to the position(s) 23 and/or 28 of SEQ ID NO: 1.
- In an embodiment, the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with amino acids 1 - 191 of SEQ ID NO: 1.
- In an embodiment, the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 80 %, at least 81 %, at least 82 %, at least 83 %, at least 84 %, at least 85 %, at least 86 %, at least 87 %, at least 88 %, at least 89 %, at least 90 %, at least 93 %, at least 95 %, at least 96 %, at least 97 %, at least 98 %, or at least 99% sequence identity with amino acids 1 - 191 of SEQ ID NO: 1.
- In an embodiment, the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with the amino acids 3 - 180 of SEQ ID NO: 2, or functional fragments thereof. In an embodiment, the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with amino acids 1 - 191 of SEQ ID NO: 2, or functional fragments thereof.
- In an embodiment the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 80 %, at least 81 %, at least 82 %, at least 83 %, at least 84 %, at least 85 %, at least 86 %, at least 87 %, at least 88 %, at least 89 %, at least 90 %, at least 93 %, at least 95 %, at least 96 %, at least 97 %, at least 98 %, or at least 99% sequence identity with amino acids 3 - 180 of SEQ ID NO: 2.
- In an embodiment, the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with SEQ ID NO: 2. In an embodiment, the GH11 xylanase enzyme comprises the inner core polypeptide of C31-4. In an embodiment, the GH11 xylanase enzyme comprises the core polypeptide of C31-4. In an embodiment, the GH11 xylanase enzyme comprises the mature polypeptide of C31-4. In an embodiment, the GH11 xylanase enzyme is a variant polypeptide having the amino acid sequence SEQ ID NO: 2.
- In an embodiment, the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with the amino acids 3 - 180 of SEQ ID NO: 2, or functional fragments thereof; wherein the amino acid sequence has at least one disulfide bridge between two cysteine residues of the polypeptide. In an embodiment, the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with amino acids 1 - 191 of SEQ ID NO: 2; wherein the amino acid sequence has at least one disulfide bridge between two cysteine residues of the polypeptide.
- In an embodiment, the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 % amino acid sequence identity with amino acids 3 - 180 of SEQ ID NO: 2, wherein the amino acid sequence has at least one disulfide bridge between two cysteine residues of the polypeptide.
- In an embodiment, the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with amino acids 3 - 180 of SEQ ID NO: 1, and wherein the amino acid sequence has at least one disulfide bridge between two cysteine residues of the polypeptide, and an amino acid substitution at the position 23 or 28, or at the positions 23 and 28, the positions corresponding to the positions 23 and 28 of the SEQ ID NO: 1.
- In an embodiment, the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with SEQ ID NO: 1, and an amino acid substitution at the positions 3, 23 and 30, the amino acid positions corresponding to the positions of the SEQ ID NO: 1. In an embodiment, the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with SEQ ID NO: 1, and an amino acid substitution at the positions 3, 28 and 30, the amino acid positions corresponding to the positions of the SEQ ID NO: 1. In an embodiment, the GH11 xylanase enzyme is a variant polypeptide comprising an amino acid sequence having at least 79 %, but less than 100 % amino acid sequence identity with SEQ ID NO: 1, and an amino acid substitution at the positions 3 and 30, the amino acid positions corresponding to the positions of the SEQ ID NO: 1.
- In an embodiment, is provided a pulp composition comprising: pulp having a pH of at least 9.5, and 0.01 - 200 g, preferably 0.1 - 20 g, more preferably 0.2 - 10 g of glycoside hydrolase family GH11 xylanase enzyme protein per 1000 kg of dry matter pulp; wherein the GH11 xylanase enzyme protein has xylanase activity. In an embodiment the GH11 xylanase enzyme, which is part of the pulp composition, has an ability to cause at least 20 %, preferably at least 25%, more preferably at least 30%, even more preferably at least 40%, most preferably at least 50% reduction in viscosity of a xylan-containing mixture at 90°C and pH 10.5 compared to the same mixture without any xylanase enzyme, wherein the xylan-containing mixture comprises 0.07 g/ml or less of xylan and 3.0 µg or less of the GH11 xylanase enzyme protein per gram of said mixture; and wherein the reduction in viscosity takes place within 20 minutes, preferably within 10 minutes, more preferably within 5 minutes and most preferably within 2 minutes.
- In an embodiment, the pulp composition has a pH of 9.5 - 11.5 and/or a temperature of 85 - 100 °C. In an embodiment, the pulp composition has a pH of at least 9.5, at least 10, at least 10.5, at least 11, or at least 11.5. In an embodiment, the pulp composition has a temperature of at least 85 °C, at least 90 °C, at least 95 °C, or at least 100 °C.
- In an embodiment, the pulp composition comprises an enzyme composition, comprising the GH11 xylanase enzyme and at least one further enzyme selected from the group consisting of protease, amylase, cellulase, β-glucosidase, lipase, xylanase, mannanase, cutinase, esterase, α-glucuronidase, phytase, nuclease, pectinase, pectinolytic enzyme, pectate lyase, carbohydrase, arabinase, galactanase, xanthanase, xyloglucanase, polysaccharide monooxygenase, laccase, peroxidase and oxidase with or without a mediator, or a combination thereof.
- In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a cellulase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a mannanase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a laccase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a peroxidase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a lignin peroxidase enzyme (EC 1.11.1.14). In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a manganese peroxidase enzyme (EC 1.11.1.13). In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a versatile peroxidase enzyme (EC 1.11.1.16). In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a dye-decolorizing peroxidase enzyme (EC 1.11.1.19). In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a haem peroxidase enzyme. In an embodiment, the pulp composition comprises an enzyme composition comprising the GH11 xylanase enzyme and a copper-based laccase enzyme (EC 1.10.3.2).
- In an embodiment, the pulp composition further comprises a surfactant, a surface-active agent, an anti-foaming agent, a defoamer, an emulsifier, a dispersant a detergent, or any combination thereof.
- In an embodiment, the pulp composition comprises 0.25 - 4 wt-% of a bleaching agent of the total weight of dry matter pulp, the bleaching agent being selected from ClO2, O3, H2O2, and peroxides.
- The xylanases and xylanase variants were designed, made and tested for xylanase enzyme stability, as described in the application
EP 20217335 - Xylanase enzyme activity was measured as described by Bailey, M.J. and Poutanen, K. 1989 in Appl. Microbiol. Biotechnol. 30:5-10, but instead of 10 minutes at 50°C and pH 5.3, after 5 minutes at 70°C and pH 7 the amount of reducing carbohydrates released from beech xylan was determined spectrophotometrically using dinitrosalicylic acid and compared to xylose standard solutions. One thermoxylanase unit, abbreviated as TXU, is defined as the amount of xylanase enzyme that produces reducing carbohydrates having a reducing power corresponding to one nmol xylose from beech xylan in one second at pH 7 and 70°C (1 TXU = 1 nkat).
- Protein amounts of purified enzyme samples were measured by absorption at 280nm. Calculated from amino acid compositions, the xylanases AM24 and C31-4 have a molecular mass without glycosylation of approximately 24 kDa and an absorption of 2.852 at 280 nm, 1 cm cuvette and 1 g pure protein per liter.
- Viscous xylan suspensions were prepared by weighting 7 g beech wood xylan into a 100 ml volumetric flask, adding aqueous pH buffer, stirring and heating until the suspensions were boiling for approximately 20 minutes. For pH 10.5 a buffer containing 7.5 g/l glycine (which equals 0.1 M glycine) and sodium hydroxide was used. For pH 7.0 a 0.1 M KH2PO4 - K2HPO4 buffer was used.
- After the xylan-containing mixtures cooled to 25 °C, the volumetric flask was filled up with buffer to the calibration mark and stirred overnight. The next day these mixtures were centrifuged, and the supernatants transferred to a baker and put into an ultrasonic bath for 15 minutes.
- Afterwards, 9 g of these supernatants were weighed into each 15 ml test tube, which test tubes were then sealed with rubber plugs and put into a water bath that was preheated to a temperature 5 °C above the measurement temperature. Then, 1 g enzyme solution, or 1 g water as a reference without enzyme addition, was added to the preheated supernatants and briefly mixed and quickly injected into the viscometer chamber, which had been preheated to the measurement temperature. Viscosity was measured with a falling sphere viscometer from Anton Paar, model DMA 4100M, over a period of 20 minutes.
- The viscosity of mixtures without enzyme addition remained high, whereas the viscosity of mixtures with specific enzymes added reduced quickly within the first minutes until approximately constant viscosity end values were reached within 20 minutes.
- The following tables summarize viscosity end values reached within 20 minutes (average values of at least duplicate measurements) at the temperature and the pH indicated for each of the tables, respectively.
Table 1. High performance difference of enzymes applied at biologically challenging conditions of 90°C and pH 10.5 was measured. 90°C and pH 10.5 Viscosity [mPa·s] Relative viscosity Comments without enzyme 2.31 100 % No viscosity reduction, reference AM24 1.84 80 % C31-4 0.72 31 % Strong viscosity reduction inactivated C31-4 2.34 101 % No viscosity reduction, control - The xylanase enzyme concentrations of AM24 and C31-4 used in these experiments were approximately 29 and 19 µg of xylanase enzyme protein per g of applied enzyme solutions, respectively. Because 1 g enzyme solution was mixed with 9 g xylan supernatant, the mixtures injected into the viscosimeter resulted in ten times diluted enzyme concentrations; and the xylan concentration was diluted from 7 g per 100 ml to 6.3 g per 100 ml.
- As a control experiment inactivated C31-4 was prepared by heating enzyme solution C31-4 to boiling for 2 hours, then removing precipitated protein. As described above, 1 g of this solution was mixed with 9 g supernatant for viscosity measurement. As expected, viscosity of this mixture was not decreased, indicating that viscosity reduction was caused by active enzyme.
Table 2. Almost no performance difference between enzymes AM24 and C31-4 applied at conditions of 80°C and pH 7.0 was measured. 80°C and pH 7.0 Viscosity [mPa·s] Relative viscosity Comments without enzyme 2.83 100 % No viscosity reduction, reference AM24 0.68 24 % Strong viscosity reduction C31-4 0.62 22 % Strong viscosity reduction - The following experiments were done as described in example 1. For pH 10 and 11 a buffer containing 7.5 g/l glycine (which equals 0.1 M glycine) and sodium hydroxide was used. For pH 8 a 0.1 M Tris buffer containing 12.1 g/l 2-amino-2-(hydroxymethyl)propane-1,3-diol and hydrochloric acid was used. For pH 9 a 0.1 M NaHCO3 - Na2CO3 buffer was used. At approximately 60 °C pH was adjusted to the desired values.
- The following tables summarize viscosity end values reached within 20 minutes at the temperature and the pH indicated for each of the tables, respectively.
Table 3. High performance difference of enzymes applied at conditions of 90°C and pH 11 was measured. 90°C and pH 11.0 Viscosity [mPa·s] Relative viscosity Comments without enzyme 2.09 100 % No viscosity reduction, reference AM24 1.88 90 % C31-4 0.99 47% Strong viscosity reduction Table 4. High performance difference of enzymes applied at conditions of 90°C and pH 10 was measured. 90°C and pH 10.0 Viscosity [mPa·s] Relative viscosity Comments without enzyme 2.34 100 % No viscosity reduction, reference AM24 1.95 83 % C31-4 0.99 42 % Strong viscosity reduction Table 5. Performance of enzymes applied at 90°C and pH 8 was measured. 90°C and pH 8.0 Viscosity [mPa·s] Relative viscosity Comments without enzyme 2.41 100 % No viscosity reduction, reference AM24 1.15 48 % C31-4 0.58 24 % Strong viscosity reduction Table 6. Almost no performance difference of enzymes applied at 85°C and pH 8 was measured. 85°C and pH 8.0 Viscosity [mPa·s] Relative viscosity Comments without enzyme 2.53 100 % No viscosity reduction, reference AM24 0.93 37 % Strong viscosity reduction C31-4 0.80 32 % Strong viscosity reduction - Short bleaching sequence XDE (step X, enzyme treatment; step D chlorine dioxide (ClO2) treatment; step E, alkaline extraction with sodium hydroxide) was used to compare the efficiency in bleaching of pre-treatments with AM24 and C31-4 xylanases at high temperature of 90°C. The pre-treatments were performed at two pH values, pH 8.3 and pH 10.5. The pulp used was oxygen delignified Eucalyptus Kraft pulp from an Asian mill with kappa number 15.5 and brightness 38.0 %-ISO. A constant ClO2 dosage (0.2 X kappa number) was used. Bleaching trials were carried out in bleaching reactors. An Anchor type Kemu reactor (batch size 0.15-1.0 kg, T max 90 °C, consistency 25 %) was used in X- and step E and an air heated Hellsten reactor (batch size 0.3-0.8 kg, T max 85 °C, consistency 12 %) in step D0.
- Approximately 2 g of enzyme protein per ton of pulp was used. Enzyme solutions of AM24 and C31-4 were applied in equal amounts. The enzyme treatment time was 60 minutes.
- After the enzyme step X the enzyme was deactivated by addition of hot water and immediately adjusting the pH of the pulp suspension to pH value 2.5-3. Brightness and kappa number were analyzed after the step E.
Table 7. Results of XDE bleaching using eucalyptus pulp. In the REF samples, no enzyme was added. The enzyme pre-treatments were performed at 90 °C using 60 min reaction time. The aCl denotes active chlorine; ΔBr denotes difference in Brightness; and Δkappa denotes a difference in Kappa number. pH 8.3 pH 10.5 REF AM24 C31-4 REF AM24 C31-4 X Initial pH 8.3 8.3 8.6 11.0 10.6 10.6 End pH 8.3 8.3 8.3 10.4 10.4 10.5 Kappa number 15.1 14.4 14.7 14.8 16.6 16.4 Brightness, %-ISO 41.5 42.2 41.9 42.0 42.6 42.4 D ClO2 cons., kg aCI/t 27.9 27.9 27.9 27.9 27.9 27.9 Initial pH 2.7 2.6 2.3 2.6 2.6 2.5 End pH 1.8 1.6 1.6 1.9 1.6 1.6 Brightness, %-ISO 55.6 56.1 57.0 56.1 55.3 57.8 E Initial pH 10.8 11.0 10.9 11.0 11.0 10.9 End pH 10.9 10.9 10.9 11.0 10.9 10.9 Kappa number 6.7 6.4 5.7 6.2 6.4 5.9 Brightness, %-ISO 56.0 57.8 58.8 57.1 56.8 59.8 aCl cons./ΔBr, kg/t* 1.53 1.41 1.34 1.46 1.49 1.28 aCl cons./Δkappa, kg/t* 3.14 3.06 2.86 3.00 3.07 2.91 - Pre-treatment with both the xylanases, AM24 and C31-4 improved the brightness of eucalyptus pulp at pH 8.3. Pulp pre-treated with C31-4 at pH 8.3 had 2.8 units higher brightness than the reference pulp and had 1.0 units higher brightness than the pulp treated with AM24. The active chlorine (aCI) used at pH 8.3 per Δkappa was 0.2 kg/t and per ΔBr 0.07 kg/t lower in the C31-4 treated pulp than in AM24 treated pulp and 0.28 kg/t and 0.19 kg/t, respectively, lower than in the reference pulp (Table 7).
- When the xylanase pre-treatments were performed at pH 10.5 and 90°C, C31-4 treated pulp had 2.7 units higher brightness and the active chlorine (aCI) use per Δkappa was 0.09 kg/t and per ΔBr 0.18 kg/t lower than in the reference pulp (Table 7).
- The measured brightness (%-ISO) increase was significant and revealed that the xylanase enzyme C31-4 application in Kraft pulp was beneficial, and effective at 90°C and pH 10.5.
- The efficiency of the xylanase enzyme C31-4 in bleaching of softwood pulp at high temperature and high pH was tested by using short bleaching sequence XDE (X, enzyme; D, ClO2 (chlorine dioxide); E, extraction with sodium hydroxide) with constant ClO2 dosage (0.2 X kappa number). Bleaching trials were carried out in bleaching reactors with whole sequence. An Anchor type Kemu reactor (batch size 0.15-1.0 kg, T max 90 °C, consistency 25 %) was used in step X and step E and an air heated Hellsten reactor (batch size 0.3-0.8 kg, T max 85 °C, consistency 12 %) in step D0.
- The pulp used in the trial was oxygen delignified SW Kraft from Scandinavian mill with following properties: kappa number 25.6, viscosity 1140 ml/g and brightness 26.8 %-ISO. The dosing of C31-4 enzyme preparation was approximately 2 g of enzyme protein per ton of pulp. The conditions used in different stages of bleaching are described in Tables 8 - 10.
- The pulp was washed three times after the step X. The first wash was done using water at reaction temperature (90 °C), followed by two washes with cold (4°C) water. After the washing steps a centrifuge treatment (2600 rpm, 10 s) was performed to remove water and about 10 - 15 g (measured as oven dry) pulp samples were collected for analysis. In addition, dry matter analysis was done from the C31-4 treated samples using IR-dryer for better adjustment of pulp amount. Kappa number and brightness were analyzed from the pulp samples.
- The results from the trial are shown in detail in Table 11.
Table 8. Conditions at step X. The pH of pulp was measured in the beginning (Target/Initial pH) and after the enzyme treatment (End pH). Pre-treatment Enzyme dosage (g/t) Pulp consistency (%) Temperature (°C) Target / Initial pH Reaction time (min) End pH No enzyme 0 10 90 10.5 / 10.6 60 10.7 C31-4 2 9.2 90 10.5 / 10.8 60 10.6 Table 9. Bleaching conditions at step D. The amount of pulp was measured as oven dry. Pre-treatment Target / used pulp (g) Dosage target / used (active. Cl % of pulp) Pulp consistency target / used (%) Temperature (°C) Initial pH / end pH Reaction time (min) Act Cl consumption (% of pulp) No enzyme 215 / 200.3 5.1 / 5.5 9 / 8.4 70 2.6 / 2.1 30 5.5 C31-4 200 / 178.2 5.1 / 5.7 9 / 8.0 70 3.1 / 2.1 30 5.6 Table 10. Bleaching condition at step E. Pre-treatment Target / used pulp amount, g (as o.d.) NaOH dosage target / used (% of pulp) Pulp consistency, target /used, % Temperature (°C) Target Initial pH / end pH Reaction time, min No enzyme 200 / 185.2 2.3 / 2.5 10/9.3 80 10.8/ 10.7 90 C31-4 185 / 159.7 2.3/2.7 10 / 8.6 80 10.7/10.7 90 Table 11. Results from the bleaching trial. Pre-treatme nt Kappa after E-stage Δ XDE kappa Δ kappa/ kg used act. Cl Bright ness after E-stage, %-ISO Δ XDE Bright ness Δ Bright ness %-ISO / kg used act. Cl Corrected end kappa number with the same 5.4 % act. Cl consumpti on Corrected end Brightness with the same 5.4% act. Cl consumpti on No enzyme 3.30 22.28 0.41 55.79 29.0 0.53 3.7 55.3 C31-4 2.52 23.06 0.41 59.38 32.6 0.58 3.5 58.0 - Softwood Kraft pulp pretreated with C31-4 at pH 10.5 had 2.7 units higher corrected end brightness with the same 5.4 % active chlorine consumption compared to reference pulp (no enzyme used).
- The bleaching test using softwood pulp and conditions like in Example 4 was repeated with the AM24 and C31-4 xylanases. The pulp was washed at pH 11 and 60 °C for about 30 minutes before its characterization and experiments. After the washing step the Kappa number of the pulp was 16.7, viscosity 1050 ml/g and brightness 32.6 %-ISO. The dosing of both enzymes (C31-4 and AM24) was 2 g of enzyme protein per ton of pulp. The conditions used in the xylanase treatment, bleaching and extraction stages are described in Tables 12 - 14. In the xylanase treatment stage (X-stage) the two enzymes were applied at different pH and temperature because the AM24 xylanase is assumed to be inactive at such pulp mill conditions while the C31-4 variant was expected, basing on previously done experiments, to be able to work at these conditions (pH 10.5/90 °C).
Table 12. Conditions of step X. The pH of pulp was measured in the beginning (Target/Initial pH) and after the enzyme treatment (End pH). Enzyme Enzyme dosage, g/t Pulp consistency, % Temper ature, °C Target / Initial pH Reaction time, min End pH 1. No enzyme - 10 90 10.5/10.4 60 10.4 2. AM24 2 10 80 7/7.1 60 7.1 3. C31-4 2 10 90 10.5/10.7 60 10.6 Table 13. Bleaching conditions of step D Enzyme D dosage*, as act. Cl % on pulp Pulp consistency, % Temp eratur e, °C Initial pH / end pH Reaction time, min Act CI consump tion, % on pulp 1. No enzyme 3.3 9 70 2.8/2.1 30 3.3 2. AM24 3.3 9 70 2.5/1.6 30 3.3 3. C31-4 3.3 9 70 2.7/1.7 30 3.3 Table 14. Conditions at step E Enzyme NaOH dosage, % on pulp Pulp consistency, % Temperature, °C Target Initial pH / end pH Reaction time, min 1. No enzyme 1.5 10 80 10.6/10.6 90 2. AM24 1.5 10 80 10.5/10.4 90 3. C31-4 1.5 10 80 10.7/10.6 90 - The results from the experiments are included in Table 15.
Table 15. Results after step E Enzyme Kappa number after E-stage ΔXDE kappa number Δkappa number / kg used act. Cl Brightness after E-stage, %-ISO ΔXDE Brightness, %-ISO Δ Brightness % / kg used act. Cl 1. No enzyme 3.0 13.7 0.41 62.3 29.7 0.89 2. AM24 2.9 13.8 0.41 63.5 30.8 0.92 3. C31-4 2.5 14.2 0.43 65.1 32.4 0.97 - Scandinavian Softwood Kraft pulp pretreated with C31-4 at pH 10.5/90 °C had a 2.8 units higher brightness compared to the reference pulp (no enzyme used) at identical conditions throughout the XDE bleaching sequence. The results confirm that C31-4 improves brightness at high pH and temperature conditions. The AM24 xylanase showed a brightness gain of 1.2 units, at adjusted conditions in the X-stage (pH 7/80 °C) and identical conditions as used for C31-4 in the D and E-stages.
- The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented in the foregoing, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention.
Claims (15)
- A bleaching process comprising:providing pulp;performing a delignification of the pulp by carrying out in the following sequence:wherein the GH11 xylanase enzyme has an ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 90 °C and pH 10.5, compared to the same mixture without any xylanase enzyme.a) an enzymatic treatment step (X) comprising contacting the pulp with a glycoside hydrolase family GH11 xylanase enzyme at a pH of at least 9.5 and a temperature of at least 85 °C;b) an oxidation step (D), wherein a bleaching agent is added;c) an alkaline extraction step (E), wherein an alkaline agent is added; andd) recovering bleached pulp;
- The process of claim 1, wherein the GH11 xylanase enzyme has an ability to cause at least 25 %, preferably at least 30 %, more preferably at least 40 % and most preferably at least 50 % reduction in viscosity of the xylan-containing mixture, compared to the same mixture without any xylanase enzyme.
- The process of claim 1 or 2, wherein the xylan-containing mixture comprises: not more than 0.07 g xylan per ml of said mixture, and not more than 3.0 µg of the GH11 xylanase enzyme protein per gram of said mixture; and
wherein the reduction in viscosity takes place within 20 minutes, preferably within 10 minutes, more preferably within 5 minutes and most preferably within 2 minutes. - The process of any preceding claim, wherein the step X comprises contacting the pulp with the GH11 xylanase enzyme at a pH 9.5 - 11.5 and a temperature of 85 - 100 °C.
- The process of any preceding claim, wherein at least 0.01 g, preferably at least 0.1 g, more preferably at least 0.2 g, most preferably at least 0.5 g of the GH11 xylanase enzyme protein is added per 1000 kg of dry matter pulp at the step X.
- The process of any preceding claim, the delignification further comprising an oxygen-delignification step (O) before the oxidation step D, wherein oxygen is added at the step O; and
wherein the step X is before or after the step O. - The process of any preceding claim, wherein the bleaching agent at the oxidation step D comprises an oxygen-containing oxidizing agent, preferably the bleaching agent is selected from a group consisting of ClO2, O3, H2O2, and peroxides.
- The process of any preceding claim, wherein the bleaching agent used is H2O2, a metal chelation step (Q) for removal of metals is performed prior to the oxidation step D, and the GH11 xylanase enzyme is added to the pulp before, during or after the chelation step Q.
- The process of any preceding claim, wherein the alkaline agent of the alkaline extraction step E is selected from NaOH, MgO, or combinations thereof.
- The process of any preceding claim, wherein the GH11 xylanase enzyme originates from bacteria, preferably from Actinobacteria, more preferably from Streptosporangiales, more preferably from Streptosporangiaceae, even more preferably from Thermopolyspora species, most preferably from Thermopolyspora flexuosa.
- The process of any preceding claim, wherein the GH11 xylanase enzyme has a molecular mass of 19 - 40 kDa, preferably 20 - 30 kDa, more preferably 23 - 25 kDa, most preferably 24 kDa, calculated from its amino acid sequence without glycosylation.
- The process of any preceding claim, wherein the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having amino acids corresponding to the amino acids 3 - 180 of SEQ ID NO: 2, or functional fragments thereof;
the GH11 xylanase enzyme having at least one disulfide bridge between two cysteine residues of the polypeptide. - The process of any preceding claim, wherein the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with the amino acids 3 - 180 of SEQ ID NO: 2, or functional fragments thereof.
- The process of any preceding claim, wherein the GH11 xylanase enzyme is a polypeptide comprising an amino acid sequence having at least 79 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 % amino acid sequence identity with the amino acids 3 - 180 of SEQ ID NO: 2, or functional fragments thereof,
wherein the amino acid sequence has at least one disulfide bridge between two cysteine residues of the polypeptide. - A pulp composition comprising:(a) pulp having a pH of at least 9.5; and(b) 0.01 - 200 g of a glycoside hydrolase family GH11 xylanase enzyme protein per 1000 kg of dry matter pulp;wherein the GH11 xylanase enzyme protein has:xylanase activity, andan ability to cause at least 20 % reduction in viscosity of a xylan-containing mixture at 90 °C and pH 10.5 compared to the same mixture without any xylanase enzyme, wherein the xylan-containing mixture comprises 0.07 g/ml or less of xylan and 3.0 µg or less of the GH11 xylanase enzyme protein per gram of said mixture; and wherein the reduction in viscosity takes place within 20 minutes.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP22157484.1A EP4230791A1 (en) | 2022-02-18 | 2022-02-18 | A bleaching process |
PCT/EP2023/052623 WO2023156215A1 (en) | 2022-02-18 | 2023-02-03 | A bleaching process |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP22157484.1A EP4230791A1 (en) | 2022-02-18 | 2022-02-18 | A bleaching process |
Publications (1)
Publication Number | Publication Date |
---|---|
EP4230791A1 true EP4230791A1 (en) | 2023-08-23 |
Family
ID=80775329
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP22157484.1A Pending EP4230791A1 (en) | 2022-02-18 | 2022-02-18 | A bleaching process |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP4230791A1 (en) |
WO (1) | WO2023156215A1 (en) |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2002057541A2 (en) * | 2001-01-18 | 2002-07-25 | Iogen Bio-Products Corporation | Use of xylanase in pulp bleaching |
WO2003062409A2 (en) * | 2002-01-25 | 2003-07-31 | Dsm Ip Assets B.V. | Thermostable enzyme compositions |
US20040112555A1 (en) * | 2002-12-03 | 2004-06-17 | Jeffrey Tolan | Bleaching stage using xylanase with hydrogen peroxide, peracids, or a combination thereof |
WO2007095398A2 (en) * | 2006-02-14 | 2007-08-23 | Verenium Corporation | Xylanases, nucleic acids encoding them and methods for making and using them |
WO2015018908A1 (en) * | 2013-08-09 | 2015-02-12 | Novozymes A/S | Reducing content of hexenuronic acids in cellulosic pulp |
WO2016135173A1 (en) * | 2015-02-25 | 2016-09-01 | Carbios | Hemicellulose-degrading compositions and uses thereof |
WO2021018751A1 (en) * | 2019-07-26 | 2021-02-04 | Novozymes A/S | Enzymatic treatment of paper pulp |
-
2022
- 2022-02-18 EP EP22157484.1A patent/EP4230791A1/en active Pending
-
2023
- 2023-02-03 WO PCT/EP2023/052623 patent/WO2023156215A1/en unknown
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2002057541A2 (en) * | 2001-01-18 | 2002-07-25 | Iogen Bio-Products Corporation | Use of xylanase in pulp bleaching |
WO2003062409A2 (en) * | 2002-01-25 | 2003-07-31 | Dsm Ip Assets B.V. | Thermostable enzyme compositions |
US20040112555A1 (en) * | 2002-12-03 | 2004-06-17 | Jeffrey Tolan | Bleaching stage using xylanase with hydrogen peroxide, peracids, or a combination thereof |
WO2007095398A2 (en) * | 2006-02-14 | 2007-08-23 | Verenium Corporation | Xylanases, nucleic acids encoding them and methods for making and using them |
WO2015018908A1 (en) * | 2013-08-09 | 2015-02-12 | Novozymes A/S | Reducing content of hexenuronic acids in cellulosic pulp |
WO2016135173A1 (en) * | 2015-02-25 | 2016-09-01 | Carbios | Hemicellulose-degrading compositions and uses thereof |
WO2021018751A1 (en) * | 2019-07-26 | 2021-02-04 | Novozymes A/S | Enzymatic treatment of paper pulp |
Non-Patent Citations (3)
Title |
---|
"Sustainable Degradation of Lignocellulosic Biomass - Techniques, Applications and Commercialization", 15 May 2013, INTECH, ISBN: 978-9-53-511119-1, article F. L. ET AL: "A Review of Xylanase Production by the Fermentation of Xylan: Classification, Characterization and Applications", XP055185297, DOI: 10.5772/53544 * |
BAILEY, M.J.POUTANEN, K, APPL. MICROBIOL. BIOTECHNOL., vol. 30, 1989, pages 5 - 10 |
KUMAR VISHAL ET AL: "Thermostable microbial xylanases for pulp and paper industries: trends, applications and further perspectives", WORLD JOURNAL OF MICROBIOLOGY AND BIOTECHNOLOGY, SPRINGER NETHERLANDS, DORDRECHT, vol. 32, no. 2, 11 January 2016 (2016-01-11), pages 1 - 10, XP035935406, ISSN: 0959-3993, [retrieved on 20160111], DOI: 10.1007/S11274-015-2005-0 * |
Also Published As
Publication number | Publication date |
---|---|
WO2023156215A1 (en) | 2023-08-24 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
Bajpai | Biological bleaching of chemical pulps | |
Buchert et al. | Application of xylanases in the pulp and paper industry | |
Kulkarni et al. | Application of xylanase from alkaliphilic thermophilic Bacillus sp. NCIM 59 in biobleaching of bagasse pulp | |
FI94265B (en) | Process for bleaching a lignocellulosic material by oxygen and enzyme treatment | |
Bajpai et al. | Biobleaching of kraft pulp | |
US7368036B2 (en) | Xylanase treatment of chemical pulp | |
Christov et al. | Repeated treatments with Aureobasidium pullulans hemicellulases and alkali enhance biobleaching of sulphite pulps | |
Wei et al. | Application of enzyme technology in biopulping and biobleaching | |
JP3261661B2 (en) | Method of using enzyme in processing and bleaching of paper pulp and apparatus using the same | |
US7320741B2 (en) | Method of xylanase treatment in a chlorine dioxide bleaching sequence | |
US7297224B2 (en) | Method of deinking waste paper using cellulase without lowering paper strength and method of evaluating the same | |
EP4230791A1 (en) | A bleaching process | |
US7541175B1 (en) | Alkaline extraction stages comprising xylanase | |
Bajpai et al. | Realities and trends in enzymatic prebleaching of kraft pulp | |
CA2003503A1 (en) | Use of aureobasidium pullulans in pulp bleaching | |
CA2541229C (en) | Modified method for mechanical pulp production | |
Valenzuela et al. | Effectiveness of novel xylanases belonging to different GH families on lignin and hexenuronic acids removal from specialty sisal fibres | |
EP0418201B1 (en) | Bleaching wood pulp with enzymes | |
Rixon et al. | Do the non-catalytic polysaccharide-binding domains and linker regions enhance the biobleaching properties of modular xylanases? | |
CN114402105A (en) | Enzymatic treatment of pulp | |
Bajpai et al. | Biobleaching | |
Viikari et al. | Enzymes in pulp bleaching | |
Moriya et al. | Enzymatic bleaching of organosolv sugarcane bagasse pulps with recombinant xylanase of the fungus Humicola grisea and with commercial Cartazyme HS xylanase | |
CA2120949A1 (en) | Method for enzymatic treatment of lignocellulosic materials, in particular cellulose pulps | |
SEPTININGRUM | Studies on Hexenuronosyl Xylooligosaccharide Degrading Enzymes from Paenibacillus species |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION HAS BEEN PUBLISHED |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |