WO2019201478A1

WO2019201478A1 - A novel process for providing eicosapentaenoic oil compositions

Info

Publication number: WO2019201478A1
Application number: PCT/EP2019/025114
Authority: WO
Inventors: V. Theocharis Koftis; Efstratios Neokosmidis; Michael TERZIDIS; Thanos Andreou
Original assignee: Nano Algae Solutions Ag
Priority date: 2018-04-20
Filing date: 2019-04-18
Publication date: 2019-10-24
Also published as: JP2021521882A; CN112218648A; EP3781190A1

Abstract

A method for manufacturing oil compositions with 20 to 70% eicosapentaenoic acid measured as weight per cent, by using simple techniques and minimizing refining steps, is provided.

Description

A NOVEL PROCESS FOR PROVIDING EIC O S APENT AEN OIC OIL

COMPOSITIONS

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of industrial processing of algal preparations deriving from N. Oculata, to provide eicosapentaenoic (EPA) oil compositions comprising about 20 to 70 % EPA in natural or synthetic forms. Such oil compositions are useful for many purposes, including food supplements or cosmetics.

BACKGROUND OF THE INVENTION

Eicosapentanoic acid (EPA) is a fatty acid containing 20 carbon atoms and 5 double bonds, all in the cis-configuration. The double bonds are located at the 5, 8, 11, 14 and 17 positions and the full chemical name is all cis 5, 8,11,14, l7-eicosapentaenoic acid.

The common abbreviation is EPA.

The human body synthesizes it from alpha-linolenic acid, which is an essential fatty acid. Consequently it is often required to replenish EPA levels. This can either be achieved by receiving EPA directly from food sources such as oily fish, or by dietary supplements containing oil compositions which comprise EPA.

EPA is available from natural sources in the form of phospholipids, tri-, di- and monoglycerides, amides, esters, or many other different types, salts and/or other compounds. In each case the EPA moiety can normally be split from the complex molecule to give the free acid form which can then be optionally linked again to other complex molecules. This allows for providing synthetic forms of EPA.

Dietary supplements containing oil compositions which comprise EPA may be provided from natural sources, such as fish, krill or algae.

Fish and krill are used for obtaining such oil compositions. However, microalgae have been recognized as a promising alternative source for lipid production. Several species of microalgae can be induced to produce specific lipids and fatty acids through relative simple manipulations of the physical and chemical properties of their culture medium. Microalgae can produce and accumulate substantial amounts of lipids (approximately 20-50% of dry weight). The accumulation of lipids in microalgae is attributed to consumption of sugars at a rate higher than the rate of cell generation, which promotes the conversion of excess sugar into lipids.

Furthermore, algae are considered a sustainable source of biomass, oils and other ingredients as a result of combining a number of advantages, including their fast growth rate, carbon dioxide consumption, non-competence with agriculture and growth in the sea.

Among many algae species utilized in obtaining fatty acids and particularly EPA, N. Oculata is considered as advantageous species because it produces EPA in higher amounts and notably does not produce decosahexanoic acid (DHA). Particularly, over two thirds of the fatty acids produced by N. Oculata consist of EPA, palmitic acid and palmitoleic acid.

There are a number of methods available for providing oil compositions comprising EPA in one of the forms mentioned above. Those methods comprise of two major parts, namely oil extraction from the algae, usually with the aid of a solvent and refinement of crude oil by a combination of methods, such as degumming, caustic neutralizing, bleaching, deodorization, winterization. In contrast to fish oils, algae oils contain considerable amounts of chlorophyll, the removal of which is an important step associated with the provision of EPA oil compositions suitable for use in food supplements, cosmetics etc Other techniques may further be utilized to provide a final product with enhanced EPA content, such as silica chromatography or formation of urea adducts.

WO2014105576 discloses methods for providing highly bioavailable EPA formulations. In those formulations EPA is available as a free fatty acid or glycolipid, or phospholipid conjugate. As disclosed therein, there is provided an algal paste subjected to extraction with organic solvents. After standard procedures to remove non lipid organic matter, the neutral lipids, including free fatty acids, di- and triglycerides are extracted and separated from the polar lipids with the aid of supercritical CO2. This extract is subsequently subjected to hydrolysis to provide free fatty acids which are then fractionized to create a concentrate of EPA free fatty acid. This concentrate is combined, in subsequent steps, with the polar lipids isolated previously, to provide the formulations of the patent application.

Alternatively, the patent application discloses a similar method as the one described above, wherein the algal paste is extracted with ethanol, treated with an alkane solvent and thereafter neutral and polar lipids are separated by means of elution from silica gel sorbent. As above, the neutral lipids are subjected to hydrolysis and further elution from a silica gel sorbent.

Both supercritical carbon dioxide and elution from silica gel sorbent are sophisticated and complicated techniques. On the other hand, oil compositions comprising EPA are known to be beneficial and useful for various purposes when comprising EPA at 20- 70% measured as weight percent.

Accordingly, there is a need to manufacture oil compositions with 20 to 70 % EPA measured as weight percent, by a cost-efficient method which utilizes simple techniques yet provides a final product with the desired EPA content.

DEFINITIONS

As used herein, the term“EPA” may refer to natural or synthetic forms of EPA. Those forms may be an ester of EPA, a salt of EPA, mono-, di- or triglyceride EPA, or the free acid form of EPA. Esters of EPA may be esters with alcohols, particularly lower alkyl alcohols, more particularly ethyl esters. Salts of EPA may be salts with amino acids, particularly with lysine. Salts of EPA may also be salts of alkali metals or alkaline earth metals. Mono-, di- or triglyceride EPA refers to a glycerol molecule esterified in one, two or all of its three available positions with one or more EPA molecules, as the case may be.

Preferable forms of“EPA” are esters of EPA with lower alkyl alcohols, salts with amino acids, free acid of EPA and mono-, di- or triglyceride EPA. More preferable is the ester of EPA with ethyl alcohol or salt with lysine. “Acid” refers to any compound that contains hydrogen and dissociates in water or solvent to produce positive hydrogen ions, as well as Lewis acids, including but not limited to acids such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, trihaloacetic acid (e.g., TFA), hydrogen bromide, maleic acid, sulfonic acids such as toluenesulfonic acids and camphorsulfonic acids, propionic acids such as (R)- chloropropionic acid, phthalamic acids such as N— [(R)-l-(l -naphthyl) ethyljphthalamic acid, tartaric acids such as L-tartaric acid and dibenzyl-L-tartaric acid, lactic acids, camphoric acids, aspartic acids, citronellic acids, BCb, BBn, and so forth. Thus, the term includes weak acids such as ethanoic acid and hydrogen sulfide; strong organic acids such as methanesulfonic acid, trifluoro acetic acid, and so forth.

“Base” when used herein includes hydroxides or alkoxides, hydrides, or compounds such as amine and its derivatives, that accept protons in water or solvent. Thus, exemplary bases include, but are not limited to, alkali metal hydroxides and alkoxides (i.e., MOR, wherein M is an alkali metal such as potassium, lithium, or sodium, and R is hydrogen or alkyl, as defined above, more preferably where R is straight or branched chain Ci_-5 alkyl, thus including, without limitation, potassium hydroxide, potassium tert-butoxide, potassium tert-pentoxide, sodium hydroxide, sodium tert-butoxide, lithium hydroxide, etc.); other hydroxides such as magnesium hydroxide (Mg(OH)₂) or calcium hydroxide (Ca(OH)₂), barium hydroxide (Ba(OH)₂); alkali metal hydrides (i.e., MH, wherein M is as defined above, thus including, without limitation, sodium, potassium, and lithium hydrides); alkylated disilazides, such as, for example, potassium hexamethyldisilazide and lithium hexamethyldisilazide; carbonates such as potassium carbonate (BGCCb), sodium carbonate (Na₂CC>3), potassium bicarbonate (KHCO3), and sodium bicarbonate (NaHCCb), alkyl ammonium hydroxides such as tetrabutyl ammonium hydroxide (TBAH) and so forth. Aqueous bases include metal hydroxides, for example, hydroxides of Group l/Group 2 metals such as Li, Na, K, Mg, Ca, etc. (e.g., aqueous LiOH, NaOH, KOH, etc.), alkyl ammonium hydroxides, and aqueous carbonates. Non-aqueous bases include but not limited to, amines and their derivatives, for example, trialkyl amine (e.g., Et3N, diisopropylethyl amine, etc.), and aromatic amine (e.g., Ph-NH₂, PhN(Me)H, etc.); alkali metal alkoxides; alkali metal hydrides; alkylated disilazides; and non-aqueous carbonates. The term“lipids” may refer to neutral or polar lipids. Polar lipids mainly comprise of glycolipids and phospholipids. Neutral lipids mainly comprise of fatty acids, triglycerides, diglycerides. Eicosapentaenoic acid (EPA) may be conjugated and be part of any of those forms, or as a free fatty acid.

The term“weight percent” refers to the amount of EPA per 100 grams of substance. It is measured by Gas Chromatography and the result is provided as % w/w assay (on as is basis). The term“purity” is measured with Gas Chromatography and refers to the amount of each chromatographically observed fatty acid ethyl ester against the total amount of all chromatographically observed compounds. It is provided as % purity of the compound that is examined. DETAILED DESCRIPTION

The present invention provides a method for treating a microalgal biomass of N. Oculata with a minimum series of steps, thereby providing an oil composition comprising from about 20% to about 70% EPA measured as a weight per cent. According to a first embodiment of the present invention, there is provided a process for the preparation of an oil composition comprising from about 20% to about 70% eicosapentaenoic acid (EPA) measured as a weight per cent, from N. Oculata algae, comprising the steps of: a) providing a microalgal biomass from N. Oculata algae; b) extracting lipids from microalgal biomass of step a by effecting disruption of the cell walls and treatment with a mixture of an aqueous and an organic phase or an organic phase, providing a crude oil extract comprising EPA; c) subjecting the crude oil extract from step b to transesterification conditions, thereby transesterifying EPA and other fatty acids to their corresponding ethyl esters and thus providing an oil phase; d) refining oil phase from step c, to provide an oil composition, comprising from about 20% to about 70% EPA, measured as a weight per cent, by subjecting it to one or more refinement methods selected from treatment with bleaching earth, winterization and treatment with urea; or c’) refining oil phase from step b to provide an oil composition, comprising from about 20% to about 35% EPA, measured as a weight per cent, by subjecting it to one or more refinement methods selected from treatment with bleaching earth, winterization, treatment with urea; d’) subjecting the crude oil extract from step c’ to transesterification conditions, thereby transesterifying EPA and other fatty acids to their corresponding ethyl esters and thus providing an oil phase; e) optionally subjecting the oil composition to further treatment, to convert EPA ethyl esters into other forms of EPA and thus provide a further oil composition.

The microalgal biomass of N. Oculata provided in step a may be freeze-dried, lyophilized or processed according to standard techniques known in the art. A useful form of microalgal biomass may be that of dry powder.

Drying the microalgal biomass is advantageous to facilitate further processing. Drying refers to the removal of free surface moisture/water from predominantly intact biomass or the removal of surface water from a slurry of homogenized (e.g. by micronization) biomass. In some cases, drying the biomass may facilitate a more efficient microalgal oil extraction process. The microalgal biomass may be dried by methods known to the skilled person. The drying method is not critical to the performance of the present invention.

The extraction of lipids from the microalgal biomass performed in step b is achieved by disrupting the cell walls and treating cell debris with an organic phase or a mixture of an aqueous phase and an organic phase.

There are a number of methods for cell disruption of algae cells available in the art and well known to the skilled person. Examples of such methods are mechanical pressing, sonication, microwave irradiation, osmotic shock, bead beating, high pressure homogenizing, blending (solid shear disruption), laser, enzyme digestion, use of solvents and combinations of any of the latter methods.

The disruption of the cell walls facilitates the extraction of the lipids by treating the disrupted cells with an organic phase or a mixture of an aqueous phase and an organic phase. The aqueous phase may be an aqueous solution of an inorganic salt, such as sodium chloride. Other aqueous phases suitable for this purpose are those containing chelating agents such as EDTA or mixture of chelating agents with inorganic salts such as NaCl, etc. Organic phase may comprise one organic solvent or a mixture of organic solvents. Exemplary solvents used for lipid extraction from algae are dichloromethane, chloroform, methanol, isopropanol, ethoxyethane, acetone, 2-ethoxyethanol, ethanol.

Step b is typically performed by effecting disruption of the cell walls, as described above and bringing them into contact with an organic phase or a mixture of an aqueous phase and an organic phase.

Step b may optionally comprise the use of an antioxidant to protect the extracted oil from oxidation during the process. Suitable antioxidants for this purpose are tocopherol,

BHT (butylated hydroxytoluene), lecithin, oregano extract, rosemary extract, citric acid and/or ascorbic acid.

The extracted lipid fraction contains predominantly lipids as defined above, with minor components of protein, carbohydrate, mineral and fiber of the biomass. After extraction of the lipids from the microalgal biomass the mixture is subjected to standard procedures, such as filtration and/or centrifugation and further treatment with one or more aqueous phases to remove undissolved solids and other minor components mentioned above. Separation of the organic phase and removal of the organic solvents provides a crude oil extract. The crude oil extract obtained in step b contains lipids which comprise, among other compounds, fatty acid, in the form of mono-, di- or triacylglycerols and free acids, including EPA. This mixture is subjected to transesterification conditions in step c, thereby converting all fatty acids, present as free fatty acids or in other forms as defined above, to the corresponding ethyl esters. Under such conditions EPA is converted to its corresponding ethyl ester as well. Transesterification conditions well known to the skilled person may include treatment with a catalytic quantity of a strong base, such as sodium or potassium hydroxide, or any other alkali metal hydroxide, in presence of a large excess of ethanol at an elevated temperature or room temperature, which leads to the conversion of the fatty acid triglycerides into the corresponding ethyl esters. The transesterification may be achieved with acidic catalyst as well. When the conversion is completed, quenching, extraction, filtration and solvent removal provides an oil phase. At this step glycerol formed by the transesterification reaction is also removed.

The removal of some other undesired oil impurities from the oil phase obtained in step c, namely chlorophyll and other pigments, polar lipids such as phospholipids, oxidation by-products, and other polar undesired compounds, is achieved in step d. The type of the oil in terms of polyunsaturated fatty acids content and impurities content challenges the efficiency of this technique and the decoloration efficiency of the method used.

The oil phase obtained in step c is therefore subjected to one or more refining methods selected from treatment with bleaching earth, winterization and treatment with urea.

Bleaching is performed with an appropriate bleaching agent. Common bleaching agents are natural clay or earth, activated clay or earth and carbon. If the oil is easily bleachable, natural clay is usually used; if the oil is not readily bleachable, acid- activated clay is used. Bentonite, sepiolite, attapulgite, Fuller’s earth, Montmorillonite are readily available bleaching agents used in oil refinement methods.

Winterization or fractionation is a technique which lies on the removal of the solids formed under controlled crystallization when the oil is subjected to subzero temperatures. The difference on the melting points and the solubility induced apart from other by the unsaturation degree and the particular configuration of each fatty acid allow the purification or enrichment of the oil in polyunsaturated fatty acids.

Urea crystallization is a technique lying on the complex formed between the urea and a saturated or mono-unsaturated fatty acid in an alcoholic solution. The complex crystallizes and is removed by filtration while the free non complexed unsaturated fatty acids remain soluble, thus the solution is enriched. The inclusion fractionation depends upon the unsaturation degree of the fatty acids rather than their physical properties such as melting point, solubility etc. Alternatively, the refining step, wherein one or more of the above mentioned refinement methods is used, may be performed directly after step b, thus being step c’. In this case, the transesterification step, namely d’, is performed right after the refining step. After transesterification of step c or d’ and refining treatments in step d or c’, an oil composition is provided, which comprises EPA from about 20% to about 70% in the form of its ethyl ester, measured as a weight per cent by Gas Chromatography assay. Step e is optional and may comprise further treatment to convert the ethyl ester of EPA comprised in the oil composition into another form, for example other esters, mono-, di- or triglycerides, salts, or the free acid. Accordingly a further oil composition may be provided via this further treatment. This includes standard methods, well known to the skilled person and may include acid or base treatment in the presence of an compound comprising a group able to form an ester bond with a carboxylic group, such as an alcohol, glycerol or an amino acid, if another ester of glyceride is desired. Alternatively, it may include treatment with a base to provide a salt of EPA or its free fatty acid form.

EXPERIMENTAL

Assay and purity were measured by Gas Chromatography using methyl docosanate as internal standard. EXAMPLE 1 : Extraction of eicosapentaenoic acid enriched triglycerides

A 2-neck 5L round bottom flask equipped with a mechanical stirrer is charged with 400 g Nannochloropsis oculata, 650 mg alpha-tocopherol, 1.2 L D.M. water, 0.4 L sodium chloride 20% wt. solution, 1.6 L dichloromethane and 0.8 L methanol. The mixture is flushed with argon and stirred for 2 hours at 20 - 25 °C. The solids are separated off by filtration and the filtrates are collected. Then, 2 L dichloromethane/methanol 2:1 mixture is added and the mixture is washed with a 3 L sodium chloride 1% wt. solution. The two layers formed are separated carefully and the lower organic layer is dried on 1 g sodium sulfate anhydrous by stirring for 30 minutes. The solvents are distilled off under reduced pressure and the oily residue is dried under high vacuum for 3 - 5 hours to afford 110 g eicosapentaenoic acid enriched triglycerides as viscous black-green oil (EPA purity as fatty acid methyl ester: 28.9 %). EXAMPLE 2: Eicosapentaenoic acid enriched ethyl esters crude mixture

A 2-neck 1 L round bottom flask equipped with magnet stirring bar, thermometer and condenser is charged under inert atmosphere with 100 g eicosapentaenoic acid enriched triglycerides and 0.3 L absolute ethanol. Then, 1.5 g potassium hydroxide is added in one-pot under inert atmosphere at 20 - 25 °C and the reaction mass is continued stirring at the same temperature for 2 - 3 hours. The reaction mass is quenched by adding 30 mL D.M. water. The solvents excess is removed under reduced pressure from the reaction mass to a final volume of ~0.2 L. The residue is diluted with 1 L cyclohexane and transferred into a 3 L separating funnel along with 0.4 L D.M. water and 0.1 L sodium chloride 20% wt. solution. The organic layer is washed and then separated off and kept aside. The aqueous layer is washed with 2 x 0.2 L cyclohexane. The extracts and washings are pooled and dried on sodium sulfate anhydrous. The solvents are distilled off in a rotary evaporator and the oily residue is dried under high vacuum for 3 - 5 hours to afford 85 g eicosapentaenoic acid enriched ethyl esters crude mixture as black-green oil (EPA purity: 30.3 %; EPA GC-assay: 20.8 %).

EXAMPLE 3: Purification of crude ethyl esters mixture by treating with montmorillonite K 10 bleaching earth

A 3-neck 3 L round bottom flask equipped with mechanical stirrer is charged with 85 g eicosapentaenoic acid enriched ethyl esters crude mixture, 0.85 L cyclohexane and 425 g montmorillonite K 10. The mixture is flushed with argon and stirred under inert atmosphere at ambient temperature for 30 minutes - 1 hour. Then, the solids are filtered off by passing the mixture through a 425 g montmorillonite K 10 filter pad under reduced pressure. The filter pad is washed with 0.85 L cyclohexane and the filtrates and washings are pooled. The solvent is removed in rotary evaporator and the oily residue is dried under high vacuum to afford 56 g eicosapentaenoic acid enriched ethyl esters mixture as light yellow oil (EPA purity: 28.9 %; EPA GC-assay: 25.6 %).

EXAMPLE 4: First enrichment of ethyl esters mixture in EPA by winterization A 100 mL round botom flask equipped with magnet stirring bar is charged with 50 g eicosapentaenoic acid enriched ethyl esters crude mixture and 2.5 mL hexane. The solution is cooled down and stirred for 5 hours at - 20 °C. Then, the crystals formed are separated off by cold filtration. The filtrates are concentrated under reduced pressure in a rotary evaporator affording 23.8 g eicosapentaenoic acid enriched ethyl esters mixture as yellow oil (48.9 %; EPA GC-assay: 46.6 %)

EXAMPLE 5 : Second enrichment of ethyl esters mixture in EPA by urea treatment A 250 mL round bottom flask equipped with magnet stirring bar is charged with 69 mL EtOH and 46 g urea. The mixture is heated up to 50 - 55 °C under stirring till a clear solution is produced. Then, 23 g of the ethyl esters mixture enriched in eicosapentaenoic acid are added slowly while stirring under inert atmosphere at 50 - 55 °C. Then, the mixture is removed from heating and allowed to reach slowly the ambient temperature (20 - 22 °C). Stirring under inert atmosphere is maintained for 20 hours. Next, the mixture is extracted with 3x200 mL hexane. The upper hexane layers are pooled and washed with 200 mL DM water. The aqueous phase is back washed with 2x50 mL hexane and the hexane layers from extraction and washings are pooled and dried on 1 g sodium sulfate anhydrous. The solvents are distilled off under reduced pressure in a rotary evaporator and the oily residue is dried under high vacuum for 3 hours to afford 7.4 g ethyl esters mixture highly enriched in eicosapentaenoic acid as yellow oil (EPA purity: 83.5 %; EPA GC-assay: 70.2 %)

Claims

1. A process for the preparation of an oil composition, comprising from about 20% to about 70% eicosapentaenoic acid (EPA) measured as a weight per cent, from N. Oculata algae, comprising the steps of:

a) providing a microalgal biomass from N. Oculata algae;

b) extracting lipids from microalgal biomass of step a by effecting disruption of the cell walls and treatment with a mixture of an aqueous and an organic phase or an organic phase, providing a crude oil extract comprising EPA;

c) subjecting the crude oil extract from step b to transesterification conditions, thereby transesterifying EPA and other fatty acids to their corresponding ethyl esters and thus providing an oil phase;

d) refining oil phase from step c , to provide an oil composition, comprising from about 20% to about 70% EPA, measured as a weight per cent, by subjecting it to one or more refinement methods selected from treatment with bleaching earth, winterization and treatment with urea;

or

c') refining oil phase from step b, to provide an oil composition, comprising from about 20% to about 70% EPA, measured as a weight per cent, by subjecting it to one or more refinement methods selected from treatment with bleaching earth, winterization and treatment with urea;

d') subjecting the crude oil extract from step c' to transesterification conditions, thereby transesterifying EPA and other fatty acids to their corresponding ethyl esters and thus providing an oil phase; and

e’) optionally su bjecting oil composition to further treatment, to convert EPA ethyl esters into other forms of EPA and thus provide a further oil composition.

2. A process, as claimed in claim 1, wherein the about 20% to about 70% eicosapentaenoic acid (EPA) measured as a weight per cent, is in a form selected from the group consisting of an ester, a salt, an acid, a mono-, di- or triglyceride or mixtures thereof.

3. A process, as claimed in claim 2, wherein the about 20% to about 70% eicosapentaenoic acid (EPA) measured as a weight per cent, is in a form selected from the group consisting of esters with lower alkyl alcohols, salts with amino acids, free acid, mono-, di- or triglycerides and combinations thereof.

4. A process, as claimed in claim 3, wherein the ester is an ethyl ester

5. A process as claimed in claim 3, wherein the salt is a salt with lysine.

6. A process, as claimed in claims 3-5, wherein treatment in step b is performed by using a mixture of an aqueous and an organic phase.

7. An oil composition obtainable by a process according to any of the preceding claims.