CN112387299B - Method for preparing L-furan serine by biomass chemical-enzymatic method - Google Patents

Abstract

The invention discloses a method for preparing L-furan serine by a biomass chemical-enzymatic method, belonging to the field of biochemical engineering. The invention provides Fe with optimized preparation process₃O₄@MCM‑41/SO₄ ^2–And the method is used for the process for producing the L-furan serine by the biomass chemical-enzymatic method. The production method of the L-furan serine omits the separation process of an intermediate, has good biocompatibility, simple steps and economic and environment-friendly process, can ensure that the yield of the L-furan serine reaches 73.6 percent, and provides reference for the green sustainable manufacture of the beta-hydroxy-alpha-amino acid.

Description

Method for preparing L-furan serine by biomass chemical-enzymatic method

Technical Field

The invention relates to a method for preparing L-furan serine by a biomass chemical-enzymatic method, belonging to the field of biochemical engineering.

Background

The utilization of the biomass can relieve the crisis of fossil energy exhaustion and environmental pollution, increases the utilization approach of waste resources and plays a supporting role in agricultural economic development.

Furfural, also known as furaldehyde, is a derivative of the furan series, which is a bio-based platform compound that can be further converted into fine chemicals and fuels. The one-step dilute acid method for producing furfural has the advantages of less equipment investment and simple operation, and is widely applied to the furfural industry. However, the conventional one-step dilute acid production process for furfural has low yield, high energy consumption and serious pollution, only hemicellulose in biomass is utilized in the process, cellulose and the like are not utilized, and the utilization rate of raw materials is low. In order to promote the further development of the furfural industry, a magnetic solid acid catalyst is researched and developed for preparing furfural, the magnetic solid acid can be quickly separated from a reaction system through an external magnetic field after the reaction is finished, and cellulose residues obtained by filtering are further hydrolyzed by cellulase to obtain glucose.

The furan serine (FLSE) belongs to furan beta-hydroxy-alpha-amino acid, is an important furfural high-added-value derivative product, and can be used as a precursor of furan antibiotics and 2-amino-1-furan-2-ethanol. In general, FLSE is synthesized by a Chemical method, but a large amount of organic solvent and strong base are consumed in the process, and the reaction is controlled to be about 4 ℃ and the reaction time is long (Dulaghan M.E., et al. journal of the American Chemical Society,1951,73(11): 5455.). Therefore, a biocatalytic method which is good in selectivity and environmentally friendly is urgently under development.

Disclosure of Invention

The invention provides an efficient one-pot chemical-enzymatic catalysis process for solving the problem of traditional organic synthesis of L-furan serine, and directly converts lignocellulose raw materials into L-furan serine. The method has the advantages of simple preparation, few steps, easy operation and economic and efficient process.

The first purpose of the invention is to provide a magnetic solid acid Fe₃O₄@MCM-41/SO₄ ^2–The method comprises the following steps of (a) to (c):

(a) mixing ferric salt and ferrous salt in a water phase according to the proportion of 2 (1-1.2), heating to over 80 ℃ under the protection of nitrogen, adding NH₃·H₂O solution, separating by magnetic field to obtain Fe₃O₄Magnetic particles;

(b) mixing fly ash with a solution containing hydrochloric acid, stirring for 4h at the temperature of more than 70 ℃, filtering, washing and drying to obtain pretreated fly ash, mixing with 2 times of sodium hydroxide by weight, and heating for 1h at the temperature of more than 500 ℃; mixing the obtained alkali fusion fly ash with water according to a ratio of 1:4, stirring for 24 hours at room temperature, and filtering to obtain a light yellow sodium silicate solution;

(c) mixing the Fe prepared in the step (a)₃O₄Dispersing in water, adding ammonia water and stirring, adding CTAB dissolved in hot water, and continuously stirring; slowly adding the sodium silicate solution prepared in the step (b), continuously reacting for 24h, adjusting the pH value to 10.5, carrying out hydrothermal treatment for 24h in a reaction kettle at the temperature of 110 ℃, carrying out magnetic separation and collecting solid productsAnd washing and drying to obtain Fe₃O₄@MCM-41。

(d) Mixing the Fe of step (c)₃O₄@ MCM-41 Mill with 3M (NH)₄)₂SO₄Soaking in the solution for at least 24h, magnetically separating, drying, and calcining at 500 deg.C for 3h to obtain solid acid Fe₃O₄@MCM-41/SO₄ ^2–。

In one embodiment, the preparation method of the magnetic solid acid specifically comprises the following steps:

(1) FeCl is added₃·6H₂O and FeCl₂·4H₂O dissolved in a stirred reactor, Fe³⁺With Fe²⁺Is 2.0: 1.1. Under the protection of nitrogen, the temperature is raised to 85 ℃, NH is added under high-speed stirring₃·H₂O solution, separating the deposited product by using a magnetic field to obtain Fe₃O₄Magnetic particles;

(2) mixing the fly ash raw material with 20% hydrochloric acid, stirring for 4h at 80 ℃, removing impurities such as iron, calcium and the like, then filtering, washing and drying to obtain pretreated fly ash, then uniformly mixing sodium hydroxide according to the weight ratio of 1:2, and heating for 1h at 550 ℃. Mixing the obtained alkali fusion fly ash with deionized water according to a ratio of 1:4, stirring for 24 hours at room temperature, and filtering to obtain a light yellow sodium silicate solution serving as a silicon source for preparing MCM-41;

(3) fe prepared in the step (1)₃O₄Dispersing in deionized water, adding ammonia water, and stirring at room temperature for 1 h. Slowly adding CTAB dissolved in hot water into Fe₃O₄Stirring was continued for 1 h. The sodium silicate solution was slowly added to the suspension and stirred slowly to allow the reaction to continue for 24 h. And adjusting the pH value of the magnetic composite material to 10.5, and carrying out hydrothermal treatment for 24h in a reaction kettle at the temperature of 110 ℃. The solid product was magnetically separated and washed with deionized water and finally dried in an oven at 60 ℃ for 24 h. The prepared Fe₃O₄@ MCM-41 was ground and used with 3M (NH)₄)₂SO₄The solution was measured at 15 mL. g^–1And soaking for 24 h. After magnetic separation and drying, calcining for 3h at 500 ℃ to obtain solid acid Fe₃O₄@MCM-41/SO₄ ^2–。

The invention also provides the magnetic solid acid Fe₃O₄@MCM-41/SO₄ ^2–Application in preparing furfural.

The invention also provides a method for preparing L-furan serine by using the biomass chemical-enzymatic method, which takes corncob powder as a raw material and adds magnetic solid acid Fe₃O₄@MCM-41/SO₄ ^2–Reacting at 160-200 ℃ for 5-180 min, adding 10 times of molar equivalent of glycine, 5-50 mu M of PLP and threonine aldolase catalyst, and reacting at 28-30 ℃.

In one embodiment, the threonine aldolase is a pure enzyme solution, or a cell expressing threonine aldolase.

In one embodiment, the L-threonine aldolase (PpLTA) is derived from the L-threonine aldolase of Pseudomonas putida (Pseudomonas putida).

In one embodiment, the L-threonine aldolase has the ability to catalyze furfural to produce L-furanserine, and has the amino acid sequence shown in SEQ ID No. 1.

In one embodiment, the method is: 200mL of high-pressure reaction kettle is filled with 100mL of deionized water, 5-10 g of corncob powder and 0.25-5 wt% of magnetic solid acid Fe₃O₄@MCM-41/SO₄ ^2–And heating and stirring at 160-200 ℃ for 5-180 min. After the reaction is finished, adjusting the pH value to 8.0, adding 10 times of molar equivalent of glycine, 5-50 mu M PLP and 5-100 g.L^–1The recombinant threonine aldolase cell with the whole cell enzyme activity of 4000-.

In one embodiment, 10g of corncob meal and 20-22 g/L of magnetic solid acid Fe are added into a reaction kettle₃O₄@MCM-41/SO₄ ^2–Heating and stirring at 160-200 ℃ for 5-180 min.

In one embodiment, the corncobs are purchased at a local produce store and ground to 40-60 mesh; preferably, the corncob particle size is 40 mesh.

In one embodiment, the method further comprises subjecting the reaction solution to separation and purification, wherein the separation and purification comprises removing the solid acid catalyst and the corncob residue from the reaction solution by magnetic separation and filtration, and extracting the reaction mixture with diethyl ether to remove unreacted furfural; adding methanol into the water phase to precipitate most of unreacted glycine, collecting the precipitated glycine and washing with methanol; dissolving the residue after methanol evaporation in phosphate buffer solution with the pH value of 8.0, and adding excessive glycine oxidase to decompose the residual glycine; purifying the enzymolysis liquid containing the aldol product after the enzymolysis treatment on anion exchange resin, eluting with 0.5 percent acetic acid, evaporating and concentrating, and crystallizing at 4 ℃ to obtain the L-furan serine.

In one embodiment, the specific steps of the separation and purification are:

(1) removing the solid acid catalyst and the corncob residues from the reaction solution through magnetic separation and filtration;

(2) extracting the reaction mixture with diethyl ether to remove unreacted furfural;

(3) adding 400mL of methanol into the water phase extracted in the step (2), incubating at 4 ℃ for 12h, collecting precipitated glycine and washing with methanol;

(4) dissolving the residue after methanol evaporation in phosphate buffer solution with pH of 8.0, and adding excessive glycine oxidase to decompose the residual glycine;

(5) purifying the enzymolysis liquid reacted in the step (4) on anion exchange resin, and eluting the resin by using 0.5 percent acetic acid;

(6) collecting the eluent in the step (5), evaporating and concentrating the eluent, and crystallizing at 4 ℃ to obtain the L-furan serine.

The invention also claims the application of the method in the preparation of products containing L-furan serine.

Has the advantages that: the invention provides a method for producing L-furan serine by a biomass chemical-enzymatic method, which omits the separation of an intermediate, has good biocompatibility, simple steps and economic and environment-friendly process, can ensure that the yield of the L-furan serine reaches 73.6 percent, and provides reference for the green sustainable manufacture of beta-hydroxy-alpha-amino acid.

Drawings

FIG. 1 is a flow chart of a chemical-enzymatic method for preparing L-furanserine.

FIG. 2 is a Scanning Electron Microscope (SEM) picture of a solid acid, wherein (a) is Fe₃O₄(ii) a (b) Is Fe₃O₄@ MCM-41; (c) is Fe₃O₄@MCM-41/SO₄ ^2–。

FIG. 3 solid acid Fe₃O₄@MCM-41/SO₄ ^2–EDAX energy spectrum of (a).

FIG. 4 is a graph of a Vibrating Sample Magnetometer (VSM) of a solid acid, (a) showing a reaction process state; (b) to magnetically separate the solid acid.

FIG. 5 product L-Furoseserine¹H NMR chart.

Detailed Description

Furfural and L-furanserine were quantified using high performance liquid Chromatography analysis, which required OPA/NAC pre-column derivatization (Gong, L., et al. Bioresource Technology,2019,293,122065; Molnar-Perl, Journal of Chromatography A,2001,913, 283-.

Example 1 solid acid Fe₃O₄@MCM-41/SO₄ ^2–Preparation of

Magnetic solid acid Fe₃O₄@MCM-41/SO₄ ^2–The preparation method comprises the following steps:

(1) FeCl is added₃·6H₂O and FeCl₂·4H₂O is dissolved in a stirred reactor, in which Fe³⁺With Fe²⁺Is 2.0: 1.1. Under the protection of nitrogen, the temperature is raised to 85 ℃, NH is dripped under the high-speed stirring of 1000r/min₃·H₂The pH value of the O solution is 11, the deposited product is separated by a magnetic field, and Fe is obtained₃O₄Magnetic particles.

(2) Mixing the fly ash raw material with hydrochloric acid with the mass fraction of 20% according to the mass ratio of 1:10, stirring for 4 hours at 80 ℃, removing impurities such as iron, calcium and the like, and then filtering, washing and drying to obtain the pretreated fly ash. Then uniformly mixing the sodium hydroxide with the pretreated fly ash according to the mass ratio of 1:2, and heating for 1h at 550 ℃. And mixing the obtained alkali fusion fly ash with deionized water according to the ratio of 1:4, stirring for 24 hours at room temperature, and filtering to obtain a light yellow sodium silicate solution serving as a silicon source for preparing MCM-41.

(3) Fe prepared in the step (1)₃O₄The magnetic particles are stirred and dispersed in the deionized water for 1 hour. CTAB dissolved in hot water at a mass ratio of 1:20 was slowly added to Fe₃O₄Stirring was continued for 1h to obtain a suspension. Slowly adding the sodium silicate solution prepared in the step (2) into the suspension, and slowly stirring to enable the reaction to be continued for 24 hours. Then the pH value of the reaction system is adjusted to 10.5, and hydrothermal treatment is carried out for 24 hours in a reaction kettle at the temperature of 110 ℃. Magnetically separating the solid product, washing with deionized water, and drying in a 60 deg.C oven for 24 hr to obtain Fe₃O₄@MCM-41。

(4) The block Fe obtained in the step (3) is₃O₄@ MCM-41 was ground into powder and used with (NH) at a concentration of 3mol/L₄)₂SO₄The solution was measured at 15mL (NH)₄)₂SO₄Solution/g Fe₃O₄Dosage of @ MCM-41 was impregnated for 24 h. After magnetic separation and drying, calcining for 3h at 500 ℃ to obtain solid acid Fe₃O₄@MCM-41/SO₄ ^2–。

The structure of the prepared solid acid was observed by an electron microscope, and the result is shown in FIG. 2, Fe₃O₄The particles are quasi-spherical and have non-uniform surfaces. In addition, there is a slight aggregation between the particles due to the magnetic dipole moment between the particles. After MCM-41 coating, the resulting material was also spherical in shape. The results show that Fe₃O₄The particles were successfully coated with MCM-41. Further elucidating Fe₃O₄The shape of the nanoparticles is not greatly changed by the functionalization process. EDAX results in FIG. 3 show that the catalyst is composed of O, Fe, Si, S, MCM-41 is coated on the surface of magnetic particles, sulfation is successfully carried out, SO is loaded on the surface of the catalyst₄ ^2-. The VSM hysteresis curve of FIG. 4 shows that Fe₃O₄And Fe₃O₄@MCM-41/SO₄ ^2-Nanoparticles have typical superparamagnetism. In addition, Fe₃O₄The magnetic saturation drops from 80 to 46emu/g, due to the presence of Fe₃O₄The nanoparticles are coated with non-magnetic MCM-41. The magnetic solid acid catalyst can be subjected to solid-solid separation from the residue through an external magnetic field, and the operation is convenient and rapid, so that the solid acid can be recycled. The results of fig. 2-4 collectively illustrate the successful preparation of the solid acid with good catalytic and separation properties.

Example 2 solid acid Fe₃O₄@MCM-41/SO₄ ^2–Preparation of furfural by catalyzing corncob

100mL of deionized water and 10g of corncob meal were added to a 200mL autoclave at a final concentration of 22g/L of the magnetic solid acid Fe prepared in example 1₃O₄@MCM-41/SO₄ ^2–The autoclave was rapidly heated to 180 ℃ by an electric heating jacket and reacted for 40min with stirring. Immediately after the reaction was complete, the reactor was immersed in an ice-water bath and cooled to room temperature.

The concentration of furfural after reaction was detected to be 72 mM.

Example 3 one-pot Synthesis of L-Furoseserine with Biomass Furfural

The recombinant L-threonine aldolase whole cell was prepared as follows: an engineered bacterium containing an L-threonine aldolase gene (the construction method of the engineered bacterium is described in Gong, L., et al. applied Biochemistry and Biotechnology,2020.DOI: org/10.1007/s12010-020-03447-y) was inoculated into a culture medium containing 50. mu.g.mL of the enzyme^–1Kanamycin was cultured overnight at 37 ℃. Then inoculating the seed in a volume of 1% (volume concentration) to a solution containing 50. mu.g.mL^–1Culturing in LB liquid medium containing kanamycin at 37 deg.C and 180rpm to OD₆₀₀0.6-1.0, adding IPTG with the final concentration of 0.2mM, carrying out induction culture at 25 ℃ for 10h, centrifuging at 8000rpm for 10min at 4 ℃ to collect wet thalli, namely recombinant L-threonine aldolase whole cells, and measuring the enzyme activity of the whole cells to be 4000-.

100mL of deionized water, 10g of corncob powder and 2 wt% of magnetic solid acid Fe are added into a 200mL high-pressure reaction kettle₃O₄@MCM-41/SO₄ ^2–And heating and stirring at 180 ℃ for 40min to generate 72mM furfural. Then, the pH of the system was directly adjusted to 8.0, 720mM glycine, 50. mu.M PLP and 20 g.L were added^–1Recombinant whole cell PpLTA is subjected to biotransformation at 30 ℃ and 200rpm to synthesize the L-furanserine. After 6h reaction, 72mM corn cob furfural was converted into 53mM L-furanserine with a yield of 73.6%.

Example 4 one-pot Synthesis of L-Furoseserine with Biomass Furfural

L-Furoseserine was synthesized according to the method of example 3, and the reaction solution after the reaction was collected and purified according to the following method: the solid acid catalyst and corncob residue were removed by magnetic separation and filtration. The reaction mixture was then extracted with diethyl ether to remove unreacted furfural. Methanol (400mL) was added to the aqueous phase and incubated at 4 ℃ for 12h to precipitate most of the unreacted glycine, which was collected and washed with methanol. The residue after evaporation of methanol was dissolved in phosphate buffer at pH 8.0 and excess Bacillus subtilis 168 derived glycine oxidase (amino acid sequence shown in SEQ ID NO.2, published in the paper Beaudoin, S.F., et al, enzyme and microbiological Technology,2018,119: 1-9) was added to decompose the remaining glycine. The aldol product was purified on an anion exchange resin and eluted with 0.5% acetic acid. Evaporating and concentrating the mixture, and crystallizing the mixture at 4 ℃ to obtain the L-furan serine.

Upon detection (see FIG. 5), purification preparation gave a solid yield of 37.8%, ee>99％，de(threo)＝20％，¹H NMR characterization results were:¹H NMR(400MHz,D₂O)δ7.56(d,J＝1.8Hz,1H),6.53–6.46(m,2H),5.29(d,J＝4.3Hz,1H),4.06(d,J＝4.3Hz,1H)。

comparative example 1 preparation of Furfural by conventional chemical Process

The specific implementation manner is the same as that of example 3, except that solid acid Fe₃O₄@MCM-41/SO₄ ^2–Replacing with inorganic acid H commonly used in the prior art₂SO₄The yield of furfural was 32mM under the same pH conditions, but the reaction was followed by the need for H₂SO₄And (4) treating the waste liquid.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

SEQUENCE LISTING

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<120> method for preparing L-furan serine by biomass chemical-enzymatic method

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Claims (8)

1. The method for preparing L-furan serine is characterized in that corncob powder is used as a raw material, and magnetic solid acid Fe with the final concentration of 20-25 g/L is added₃O₄@MCM-41/SO₄ ^2–Reacting at 160-200 ℃ for 5-180 min to prepare furfural, adding 10 times of molar equivalent of glycine to the furfural, reacting at 28-30 ℃ with PLP and threonine aldolase with final concentration of 5-50 mu M;

wherein the magnetic solid acid Fe₃O₄@MCM-41/SO₄ ^2–The preparation process of (a) to (c) is as follows:

(a) mixing ferric salt and ferrous salt in a molar ratio of 2 (1-1.2) in an aqueous phase, and heating to 8 ℃ under the protection of nitrogenAt a temperature above 0 ℃, adding NH₃·H₂O solution, separating by magnetic field to obtain Fe₃O₄Magnetic particles;

(b) mixing fly ash with a solution containing hydrochloric acid, stirring for 4 hours at the temperature of more than 70 ℃, filtering, washing and drying to obtain pretreated fly ash, mixing with 2 times of sodium hydroxide by weight, and heating for 1 hour at the temperature of more than 500 ℃ to obtain alkali fusion fly ash; mixing the obtained alkali fusion fly ash with water according to the mass ratio of 1:3-5, stirring for at least 20h, and filtering to obtain a light yellow sodium silicate solution;

(c) mixing the Fe prepared in the step (a)₃O₄Dispersing magnetic particles in water, adding ammonia water and stirring, adding a CTAB aqueous solution, adding the sodium silicate solution prepared in the step (b), reacting for at least 20h, adjusting the pH value to 10-11, carrying out heat treatment at 100-120 ℃ for at least 20h, carrying out magnetic separation to collect a solid product, cleaning, and drying to obtain Fe₃O₄@MCM-41；

(d) Mixing the Fe of step (c)₃O₄@ MCM-41 in (NH)₄)₂SO₄Soaking in the solution for at least 24h, magnetically separating and drying, and calcining at 450-550 ℃ for 2-3h to obtain solid acid Fe₃O₄@MCM-41/SO₄ ^2–。

2. The method according to claim 1, wherein the threonine aldolase is a pure enzyme solution or a microbial cell expressing threonine aldolase.

3. The method of claim 1, wherein said threonine aldolase is derived from Pseudomonas putida.

4. The method according to claim 2, wherein the wet cell concentration of the threonine aldolase-expressing microbial cell in the reaction system is 5 to 100 g/L.

5. The method of claim 1, wherein the corncob has a particle size of 40-60 mesh.

6. The method according to any one of claims 1 to 5, wherein the reaction solution after the reaction is further subjected to separation and purification treatment.

7. The method according to claim 6, wherein the specific steps of separating and purifying are as follows:

(1) removing the solid acid catalyst and the corncob residues from the reaction solution through magnetic separation and filtration;

(2) extracting the reaction mixture with diethyl ether to remove unreacted furfural;

(3) adding 400mL of methanol into the water phase extracted in the step (2), incubating at 4 ℃ for 12h, collecting precipitated glycine and washing with methanol;

(4) dissolving the residue after methanol evaporation in phosphate buffer solution with pH of 8.0, and adding excessive glycine oxidase to decompose the residual glycine;

(5) purifying the enzymolysis liquid reacted in the step (4) on anion exchange resin, and eluting the resin by using 0.5 percent acetic acid;

(6) collecting the eluent in the step (5), evaporating and concentrating the eluent, and crystallizing at 4 ℃ to obtain the L-furan serine.

8. Use of a process according to any one of claims 1 to 7 for the preparation of a furfural and/or L-furanserine containing product.

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