阅读说明：本技术 使用电渗析技术拆分光学异构体的方法 (Method for resolving optical isomers using electrodialysis techniques ) 是由 邱贵森 苏金环 曾聪明 蒋泰隆 陈彦 刘文杰 于 2019-02-27 设计创作，主要内容包括：本发明提供了一种通过电渗析从外消旋体中拆分光学异构体的方法。具体地,本发明将电渗析技术应用于酶拆分工艺中,主要应用于酶拆分后产物的分离。以D-泛解酸内酯制备工艺为例,关键点在于通过电渗析方法从酶拆分液中分离D-泛解酸和L-泛解酸内酯,取代了现有的有机溶剂提取方法,工艺方法简单易行,D-泛解酸收率高,纯度好,大大减少了有机溶剂的使用量,降低了生产成本,环境友好,可以很大程度的改善工人的工作环境,提高运行安全指数。本发明所提供的方法在酶拆分分离工艺中有很大的应用潜力。(The present invention provides a method for resolving optical isomers from racemates by electrodialysis. Specifically, the electrodialysis technology is applied to the enzyme resolution process, and is mainly applied to separation of products after enzyme resolution. Taking a preparation process of D-pantoic acid lactone as an example, the key point is that D-pantoic acid and L-pantoic acid lactone are separated from an enzyme resolution liquid by an electrodialysis method, the existing organic solvent extraction method is replaced, the process method is simple and feasible, the yield of the D-pantoic acid is high, the purity is good, the use amount of the organic solvent is greatly reduced, the production cost is reduced, the environment is friendly, the working environment of workers can be improved to a great extent, and the operation safety index is improved. The method provided by the invention has great application potential in an enzyme resolution and separation process.)

1. A method of resolving optical isomers from racemates by electrodialysis, comprising:

a) reacting the racemate in the presence of a catalyst to form a mixture comprising an ionizable form of the first optical isomer and a non-ionizable form of the second optical isomer;

b) subjecting the mixture to an electrodialysis treatment to allow the ionizable form of the first optical isomer and the non-ionized form of the second optical isomer to be separated; and

c) collecting the separated ionizable form of the first optical isomer, and/or collecting the separated nonionized form of the second optical isomer.

2. The method of claim 1, wherein the racemate has a hydrolyzable functional group.

3. The method of claim 2, wherein the functional group is hydrolyzed to form an ionizable group.

4. A method as claimed in any one of claims 2 to 3 wherein the catalyst specifically hydrolyses the hydrolysable functional groups in the first optical isomer thereby to produce an ionisable form of the first optical isomer.

5. The method of any one of claims 1 to 4 wherein the racemate has a ring structure and the hydrolysable functional group is in the ring structure.

6. The method of claim 5, wherein the ring structure comprises a lactone and a lactam.

7. The method of any one of claims 5-6, wherein the ring structure is open-ring in the ionizable form of the first optical isomer.

8. The method of any of claims 1-7, wherein the catalyst comprises an enzyme composition.

9. The method of claim 8, wherein the enzyme composition comprises an ester hydrolase and/or a lactamase.

10. The method of any of claims 8-9, wherein the enzyme composition comprises a purified enzyme, a cell expressing an enzyme, or a lysate of a cell expressing an enzyme.

11. The method of any one of claims 8-10, wherein the enzyme composition is immobilized on a substrate.

12. The method of any one of claims 1-11, further comprising after step a) and before step b): removing the catalyst residue from the mixture.

13. The method of any one of claims 1-12, further comprising purifying and/or concentrating the isolated ionizable form of the first optical isomer, and/or purifying and/or concentrating the isolated nonionized form of the second optical isomer.

14. The method of any one of claims 1-13, further comprising converting the non-ionized form of the second optical isomer into the racemate.

15. A process as claimed in any one of claims 1 to 14, wherein the electrodialysis treatment is carried out in an electrodialysis cell having a depletion compartment and a concentration compartment separated by an ion exchange membrane.

16. A method as defined in claim 15, wherein the electrodialysis treatment comprises placing the mixture in the depletion compartment and a solvent in the concentration compartment, and energizing the electrodialysis cell causes the ionizable form of the first optical isomer in the depletion compartment to migrate into the solvent in the concentration compartment.

17. The method of claim 16, wherein the solvent comprises pure water.

18. The method of any of claims 15-17, wherein the ion exchange membrane is a homogeneous membrane or a heterogeneous membrane.

19. A process as claimed in any one of claims 15 to 18, wherein the electrodialysis treatment is carried out in one electrodialysis cell, or in more than one electrodialysis cell in series.

20. The method of any one of claims 1-19, wherein the racemate is DL-pantoic acid lactone, the ionizable form of the first optical isomer is D-pantoic acid, and the nonionized form of the second optical isomer is L-pantoic acid lactone.

21. The method according to any one of claims 1 to 19, wherein the racemate is methyl 3-cyclohexene-1-carboxylate, the ionizable form of the first optical isomer is (R) -3-cyclohexene-1-carboxylate, and the nonionizable form of the second optical isomer is methyl (S) -3-cyclohexene-1-carboxylate.

22. The method of any one of claims 1-19, wherein the racemate is α -hydroxy- γ -butyrolactone, the ionizable form of the first optical isomer is (R) - α -hydroxy- γ -butanoic acid, and the non-ionizable form of the second optical isomer is (S) - α -hydroxy- γ -butyrolactone.

23. The method of any one of claims 1 to 19, wherein the racemate is β -hydroxy- γ -butyrolactone, the ionizable form of the first optical isomer is (R) - β -hydroxy- γ -butanoic acid, and the non-ionizable form of the second optical isomer is (S) - β -hydroxy- γ -butyrolactone.

24. The method of any one of claims 1-19, wherein the racemate is α -acetyl- γ -butyrolactone, the ionizable form of the first optical isomer is (R) - α -acetyl- γ -butanoic acid, and the non-ionizable form of the second optical isomer is (S) - α -acetyl- γ -butyrolactone.

25. The process according to any one of claims 1 to 24, wherein the catalyst is D-pantolactone hydrolase, Novozyme435 lipase, α -hydroxy- γ -butyrolactone hydrolase, β -hydroxy- γ -butyrolactone hydrolase or α -acetyl- γ -butyrolactone hydrolase.

Technical Field

The invention belongs to the field of biotechnology, and particularly relates to a method for resolving optical isomers from racemes by using a biocatalysis technology and an electrodialysis technology.

Background

Chirality is an essential attribute of nature, and many biological macromolecules and biologically active substances have chiral characteristics. Although the chemical components of two or more different configurations of the chiral substance are completely the same, the physiological activities are often different, only one configuration usually has the required activity, and the other configurations have little or no effect and even have toxic or side effects. Such as pantothenic acid (pantothenic acid), also known as bendocinic acid, is one of the vitamins of the B group, is a component of coenzyme A, is involved in the metabolism of proteins, fats and sugars, and plays an important role in substance metabolism. The active ingredient is D-configuration D-pantothenic acid (vitamin B5), but because of its instability, it is mainly available in the form of calcium D-pantothenate.

Resolution is one of the main routes of acquisition of optically pure chiral compounds. Compared with the traditional chemical resolution method, the enzymatic resolution method does not need to use a resolution reagent with high price, has mild reaction conditions, good optical selectivity and environmental friendliness, and can also carry out reactions which cannot be carried out by a chemical method. The enzyme method separation is more and more advocated by scientific researchers of various countries by virtue of the obvious advantages of the enzyme method separation, and has already been subjected to a plurality of industrial success cases.

For example, D-Pantolactone (D-Pantolactone) is an important chiral intermediate for the production of the pantothenic acid series, such as calcium D-pantothenate, D-panthenol, and D-pantethine. At present, the industrial synthesis of D-pantoic acid lactone mostly adopts a technical route combining a chemical method and a hydrolytic enzyme resolution method. Namely, racemic DL-pantoic acid lactone is produced by a chemical method, then D-pantoic acid lactone hydrolase is used for hydrolysis and resolution, the clear liquid of the resolution reaction is firstly extracted by an organic solvent to obtain the L-pantoic acid lactone and unreacted D-pantoic acid lactone, and the water phase (containing D-pantoic acid) is added with acid for lactonization and then is extracted by the organic solvent, and then desalinization and decoloration are carried out, and the product is refined by a recrystallization method. For example, in CN1313402A, DL-pantoic acid lactone is resolved by using free or immobilized cells, then dichloromethane is used for extraction, aqueous phase hydrochloric acid is used for acidification and then dichloromethane is used for extraction, and D-pantoic acid lactone crude product obtained after solvent recovery is recrystallized in acetone/isopropyl ether to obtain qualified D-pantoic acid lactone. The process has the disadvantages of low yield and high cost, for example, a large amount of organic solvent is used for extraction in the process of extracting and refining D-pantoic acid obtained by enzyme reaction, which causes environmental and cost problems, and the crude D-pantoic acid lactone is required to be recrystallized and refined.

Electrodialysis is an electrochemical separation process that separates electrolyte components from aqueous solutions using the action of ion exchange membranes and a direct current electric field.

Disclosure of Invention

The invention provides a brand new method for splitting optical isomers. The method can make up the defects of the existing chiral resolution process, and replaces the traditional organic solvent extraction process with electrodialysis technology by utilizing different ionization degrees of optical isomers in the chiral resolution product, thereby improving the yield and the quality of the product and reducing the production cost.

The present invention provides a method for resolving optical isomers from racemates by electrodialysis, comprising:

a) reacting the racemate in the presence of a catalyst to form a mixture comprising an ionizable form of the first optical isomer and a non-ionizable form of the second optical isomer;

b) subjecting the mixture to an electrodialysis treatment to allow the ionizable form of the first optical isomer and the non-ionized form of the second optical isomer to be separated; and

c) collecting the separated ionizable form of the first optical isomer, and/or collecting the separated nonionized form of the second optical isomer.

In the present application, "racemic body" means a mixture having two or more optical isomers with different optical rotation properties. For example, a compound having one chiral center may have two optical isomers, one having a chiral center of the R configuration and the other having a chiral center of the S configuration. For this compound, the racemate includes both an optical isomer in the R configuration and an optical isomer in the S configuration. In the racemates described herein, the different optical isomers may be present in equal molar amounts (i.e., optical rotation offsets) or may be present in unequal molar amounts.

In certain embodiments, the racemate has hydrolyzable functionality. Hydrolyzable functional groups such as, but not limited to, ester linkages, amide linkages, and the like. In certain embodiments, the functional group can be hydrolyzed to form an ionizable group. Ionizable groups refer to groups that ionize in aqueous solution, e.g., carboxyl, amino, and the like. Ionizable groups, upon ionization, produce charged groups such as negatively charged carboxylates, positively charged ammonia ions, and the like. In certain embodiments, the chiral center in the racemate may be located in or near the hydrolyzable functional group, for example on an atom adjacent to the hydrolyzable functional group, or at a position spaced 1, 2 or 3 atoms from it.

In the method of the invention, the catalyst can specifically react with (e.g. hydrolyze a hydrolyzable functional group in) a particular optical isomer in the racemate to render it ionizable. By "ionizable form" is meant herein that it ionizes to form charged groups in aqueous solution. In certain embodiments, the ionizable form can comprise an ionizable group, such as a carboxyl group, an amino group, and the like. In certain embodiments, the catalyst may not catalyze the second optical isomer in the racemate, leaving it in its non-ionized form. By "non-ionized form" is meant herein that it does not ionize in aqueous solution, nor has charged groups. In certain embodiments, the non-ionized form comprises a non-ionized group, such as an ester (e.g., a lactone in a racemate), an amide, an ether, and the like.

In certain embodiments, the racemate has a ring structure, and the hydrolyzable functional group may be in the ring structure. Exemplary ring structures are, for example, lactones, lactams. These intra-ring functional groups can react to open the ring. In certain embodiments, the ring structure is closed-loop in the non-ionized form of the second optical isomer. In certain embodiments, the ring structure is open-looped in the ionizable form of the first optical isomer. For example, when a ring-opening reaction occurs with an intra-ring functional group, an ionizable group is formed. Or in certain embodiments, the ring structure is open in the non-ionized form of the second optical isomer, and/or closed in the ionizable form of the first optical isomer. In a racemate having a ring structure, the chiral center may or may not be present at a ring atom.

In certain embodiments, the racemate is an ester. Exemplary racemic esters include, methyl 3-cyclohexene-1-carboxylate. In certain embodiments, the racemate is a lactone. The lactone means that it has an intramolecular ester bond (-C (O) formed by dehydration of a carboxyl group and a hydroxyl group in its molecular structure. Usually the intramolecular ester bond is in a ring structure. Examples of lactones are, for example, DL racemohydropantoic acid lactone, β -butyrolactone, γ -butyrolactone, α -hydroxy- γ -butyrolactone, β -hydroxy- γ -butyrolactone, α -acetyl- γ -butyrolactone, n-butylphthalide and the like.

In certain embodiments, the catalyst comprises an enzyme composition. In certain embodiments, the enzyme composition comprises an enzyme that is capable of specifically reacting with an optical isomer. For example, specifically with the D-configuration optical isomer, or specifically with the L-configuration optical isomer. In certain embodiments, the enzyme composition comprises an ester hydrolase. In certain embodiments, the ester hydrolase specifically catalyzes the D-configuration of a lactone. Exemplary ester hydrolyzing enzymes include, for example, D-pantolactone hydrolase, Novozyme435 lipase, beta-butyrolactone hydrolase, gamma-butyrolactone hydrolase, alpha-hydroxy-gamma-butyrolactone hydrolase, beta-hydroxy-gamma-butyrolactone hydrolase, alpha-acetyl-gamma-butyrolactone hydrolase, n-butylphthalide hydrolase, and the like. Taking D-pantoic acid lactone hydrolase as an example, the hydrolase can specifically hydrolyze D-configuration pantoic acid lactone in a racemate, so that lactone structures in the D-configuration pantoic acid lactone are hydrolyzed to form intramolecular independent carboxyl and hydroxyl, wherein the carboxyl can be ionized in aqueous solution and can be charged and can be in an ionizable form. However, the D-pantoic acid lactone hydrolase can not hydrolyze L-configuration pantoic acid lactone in a racemate, so that the L-configuration pantoic acid lactone still keeps a lactone structure in a non-ionized form after catalytic reaction. As another example, Novozyme435 lipase can specifically hydrolyze R-configured methyl 3-cyclohexene-1-carboxylate in the racemate to form 3-cyclohexene-1-carboxylate, which is ionizable in aqueous solutions. Methyl 3-cyclohexene-1-carboxylate in the S-configuration remains in its non-ionised form since it cannot be hydrolysed.

In certain embodiments, the enzyme composition comprises a lactamase. In certain embodiments, the lactamase specifically catalyzes a D-configuration lactam. Exemplary lactamases are, for example, beta-lactamases, gamma-lactamases. Taking beta-lactamase as an example, the beta-lactamase can specifically hydrolyze D-configuration beta-lactam in a racemate, so that the lactam structure in the beta-lactam is hydrolyzed to form intramolecular independent carboxyl and amino, wherein the carboxyl can be ionized in aqueous solution and can be charged and can be in an ionizable form. However, the beta-lactamase can not hydrolyze the L-configuration beta-lactam in the racemate, so the L-configuration beta-lactam still maintains the lactam structure after the catalytic reaction and is in a non-ionized form.

In certain embodiments, the racemate according to the invention is DL-pantoic acid lactone, the first optical isomer is D-pantoic acid lactone, the second optical isomer is L-pantoic acid lactone, the ionizable form of the first optical isomer is D-pantoic acid, and the nonionized form of the second optical isomer is L-pantoic acid lactone.

In certain embodiments, the racemate is methyl 3-cyclohexene-1-carboxylate, the first optical isomer is methyl (R) -3-cyclohexene-1-carboxylate, the second optical isomer is methyl (S) -3-cyclohexene-1-carboxylate, the ionizable form of the first optical isomer is (R) -3-cyclohexene-1-carboxylate, and the nonionized form of the second optical isomer is methyl (S) -3-cyclohexene-1-carboxylate.

In certain embodiments, the racemate is α -hydroxy- γ -butyrolactone, the first optical isomer is (R) - α -hydroxy- γ -butyrolactone, the second optical isomer is (S) - α -hydroxy- γ -butyrolactone, the ionizable form of the first optical isomer is (R) - α -hydroxy- γ -butanoic acid, and the non-ionized form of the second optical isomer is (S) - α -hydroxy- γ -butyrolactone.

In certain embodiments, the racemate is β -hydroxy- γ -butyrolactone, the first optical isomer is (R) - β -hydroxy- γ -butyrolactone, the second optical isomer is (S) - β -hydroxy- γ -butyrolactone, the ionizable form of the first optical isomer is (R) - β -hydroxy- γ -butyrate, and the non-ionized form of the second optical isomer is (S) - β -hydroxy- γ -butyrolactone.

In certain embodiments, the racemate is α -acetyl- γ -butyrolactone, the first optical isomer is (R) - α -acetyl- γ -butyrolactone, the second optical isomer is (S) - α -acetyl- γ -butyrolactone, the ionizable form of the first optical isomer is (R) - α -acetyl- γ -butyrate, and the non-ionized form of the second optical isomer is (S) - α -acetyl- γ -butyrolactone.

Any form of enzyme having a selective catalytic function for optical isomers may be used. In certain embodiments, the enzyme composition may contain a purified enzyme, a cell expressing an enzyme, or a lysate of a cell expressing an enzyme. The cell expressing the enzyme may be any suitable host cell, either prokaryotic, such as bacteria, or eukaryotic, such as yeast, animal cells, and the like. The cell lysate can be any component of a lysate containing an enzyme, such as a cell lysate or the like. In certain embodiments, the enzyme composition is immobilized on a substrate. Suitable substrates may include materials for immobilized enzymes, such as magnetic particles, macroporous resins, and the like; materials for immobilizing the cells, such as calcium alginate, gels, and the like, may also be included.

In certain embodiments, the step a) maintains the pH in the range of 7.0 to 7.5 during the reaction, for example, the pH is maintained at 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, or any value between any two of the above numerical ranges. In certain embodiments, 15N NH is used₃.H₂O-titration maintained the pH. In certain embodiments, the temperature of step a) during the reaction is maintained between 20 ℃ and 40 ℃, e.g., 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 DEG C27 ℃, 28 ℃, 29 ℃, 30 ℃, 31 ℃, 32 ℃, 33 ℃, 34 ℃, 35 ℃, 36 ℃, 37 ℃, 38 ℃, 39 ℃, 40 ℃ or any value between any two value ranges above. In certain embodiments, the reaction time of step a) is 1 to 10 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any value between any two of the above numerical ranges.

In certain embodiments, after step a) and before step b), further comprising: removing the catalyst residue from the mixture. The residue includes cell debris, proteins and other macromolecules, and the residue of the catalyst in the mixture can be removed by a person skilled in the art according to the actual need by using conventional separation means, such as one or more of filtration, centrifugation, microfiltration, ultrafiltration and the like.

In certain embodiments, the filtration is achieved by using filter paper or filter cloth. The filter paper or filter cloth in the present invention may be commercially available filter paper or filter cloth, such as those manufactured by GE Healthcare Life Sciences, Shibi pure, Asahi chemical Co. In certain embodiments, the filter paper or filter cloth has a pore size of 10 to 150 μm, such as 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, or any number between any two of the above numerical ranges. One skilled in the art can select a suitable filter paper or filter cloth pore size to remove the catalyst residue according to the type and size of the catalyst residue.

In certain embodiments, the centrifugation is achieved by using a centrifugal separator. The centrifugal separator of the present invention may be a commercially available centrifugal separator, such as those manufactured by Guangzhou Fuyi liquid separation technology, Inc., cigarette counter Chengbo mechanical technology, Inc., Yao electric technology, Inc. of Dongguan, TEMA System, Kyte, Heinkel, GEA, etc. In certain embodiments, the centrifugation rate is 1000rpm to 2000rpm, such as 1000rpm, 1100rpm, 1200rpm, 1300rpm, 1400rpm, 1500rpm, 1600rpm, 1700rpm, 1800rpm, 1900rpm, 2000rpm, or any value between any two of the above numerical ranges. In certain embodiments, the centrifugation time is 2 to 15 minutes, e.g., 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, or any value between any two of the above numerical ranges. One skilled in the art can select a proper centrifugation speed and centrifugation time to remove the catalyst residue according to the kind and size of the catalyst residue.

In certain embodiments, the microfiltration is achieved by passing the mixture through a microfiltration membrane. The microfiltration membrane according to the present invention may be a commercially available microfiltration membrane, such as a microfiltration hollow fiber membrane series produced by GE Healthcare Life Sciences, Shibi pure, Asahi chemical Co. In certain embodiments, the pore size of the microfiltration membrane is between 0.1 μm and 0.6 μm, such as 0.1 μm, 0.15 μm, 0.2 μm, 0.22 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, or any value between any two of the above numerical ranges. Depending on the size of the catalyst residue, the selection of a microfiltration membrane pore size as small as possible facilitates the removal of large particle residues.

In certain embodiments, the ultrafiltration is achieved by passing the mixture through an ultrafiltration membrane. The ultrafiltration membrane of the present invention may be a commercially available ultrafiltration membrane, such as a hollow fiber ultrafiltration membrane series produced by GE Healthcare Life Sciences, Shibi pure, Asahi chemical company, and the like. In certain embodiments, the ultrafiltration membrane is a hollow fiber ultrafiltration membrane having a pore size of from 10kD to 500kD, such as a hollow fiber ultrafiltration membrane having a pore size of 10kD, 20kD, 30kD, 40kD, 50kD, 60kD, 70kD, 80kD, 90kD, 100kD, 150kD, 200kD, 250kD, 300kD, 350kD, 400kD, 450kD, 500kD, or any value in between any two of the above numerical ranges. One skilled in the art can select a suitable ultrafiltration membrane pore size to remove the catalyst residue according to the size of the catalyst residue.

In certain embodiments, the methods of the present invention further comprise purifying and/or concentrating the isolated ionizable form of the first optical isomer, and/or purifying and/or concentrating the isolated nonionized form of the second optical isomer.

In certain embodiments, the isolated ionizable form of the first optical isomer and/or the non-ionizable form of the second optical isomer can be further purified. For example, the ionizable form of the first optical isomer and/or the non-ionizable form of the second optical isomer can be extracted by using a suitable solvent. For example, an organic solvent (e.g., ethyl acetate) may be added to the collected (R) -3-cyclohexene-1-carboxylic acid, and the organic phase may be collected to obtain purified (R) -3-cyclohexene-1-carboxylic acid. For another example, an organic solvent (e.g., ethyl acetate) may be further added to the collected methyl (S) -3-cyclohexene-1-carboxylate, and the organic phase may be collected to obtain a purified methyl (S) -3-cyclohexene-1-carboxylate.

In certain embodiments, the isolated and/or purified ionizable form of the first optical isomer and/or the non-ionized form of the second optical isomer can be further concentrated. In certain embodiments, the concentration is achieved by reduced pressure, e.g., the isolated and/or purified ionizable form of the first optical isomer and/or the isolated and/or purified nonionized form of the second optical isomer is pumped to a concentration device for concentration under reduced pressure.

In certain embodiments, the invention further comprises converting the non-ionized form of the second optical isomer into the racemate. The non-ionized form of the second optical isomer may have been isolated by the methods provided herein, or further purified, or further concentrated. For example, when the racemate is an ester, the non-ionized form of the second optical isomer that is separated (i.e., the ester) can be racemized to give a racemate having a different chiral isomer. By reconverting the resolved second optical isomer to the racemate, it may allow further chiral resolution by the methods provided herein to obtain more of the first optical isomer.

In certain embodiments, the invention further comprises converting the ionizable form of the separated first optical isomer into a non-ionizable form. In certain embodiments, the ionizable form of the isolated (and/or purified or concentrated) first optical isomer can be further reacted to restore the ionizable groups thereof to hydrolyzable functionality. For example, in certain embodiments, the ionizable form of the isolated first optical isomer is D-pantoic acid, which can be lactonized to yield D-pantoic lactone, thereby restoring the ionizable group (i.e., carboxyl group) therein to a hydrolyzable functionality (i.e., lactone).

The electrodialysis step in the process of the invention can be carried out by a person skilled in the art using known methods and equipment. The device and method for electrodialysis are described in the "industry Standard of the people's republic of China-electrodialysis technology HY/T034.1-034.5-1994".

In certain embodiments, the electrodialysis treatment is performed in an electrodialysis cell having a depleting compartment and a concentrating compartment separated by an ion exchange membrane. In certain embodiments, the ion exchange membrane is a homogeneous membrane or a heterogeneous membrane. During the electrodialysis process, anions and cations migrate toward the anode and cathode, respectively, under the drive of an applied electric field, using the permselectivity of the ion exchange membrane (e.g., cations can permeate through the cation exchange membrane and anions can permeate through the anion exchange membrane).

A variety of ion exchange membranes known in the art can be selected by those skilled in the art to perform electrodialysis, depending on their practical needs. In certain embodiments, the ion exchange membrane is an anion exchange membrane, such as a Q membrane. In certain embodiments, the ion exchange membrane is a cation exchange membrane, such as an S-membrane. In certain embodiments, the ion exchange membranes are cation exchange membranes and anion exchange membranes. In certain embodiments, the cation exchange membrane allows cations to pass through while repelling blocking anions. In certain embodiments, the anion exchange membrane allows anions to pass through while repelling blocks cations from passing through. In some embodiments, the compartments formed between the cation exchange membrane and the anode and between the anion exchange membrane and the cathode are concentrating compartments, and the compartments formed between the cation membrane and the anion membrane are depleting compartments. In certain embodiments, the cation exchange membranes and anion exchange membranes are commercially available, for example, from Novasep, Eurodia, shandongtianwei membrane technologies, ltd, seiku water treatment, and the like.

In certain embodiments, the skilled person may select the membrane stack size of the homogeneous or heterogeneous membrane according to their actual needs, e.g. 10 x 20cm, 10 x 30cm, 20 x 30cm, etc. In certain embodiments, the number of membrane pairs of the homogeneous or heterogeneous membranes can be selected by one skilled in the art according to their actual needs, e.g., 5 pairs, 10 pairs, 15 pairs, 20 pairs, etc.

In certain embodiments, the electrodialysis process comprises placing the mixture in the depletion compartment and a solvent in the concentration compartment, and energizing the electrodialysis cell such that the ionizable form of the first optical isomer in the depletion compartment migrates into the solvent in the concentration compartment.

In some embodiments, the flow rate is adjusted during the electrodialysis treatment to adjust the pressure in the concentration compartment and the desalination compartment such that the pressure in the concentration compartment is 1 time, 2 times, 3 times, 4 times, 5 times or any value between any two of the above numerical ranges. In certain embodiments, the electrodialysis treatment is performed at a constant voltage until the conductivity of the depleting compartments is less than 30 μ s/cm, 40 μ s/cm, 50 μ s/cm, 60 μ s/cm, 70 μ s/cm, 80 μ s/cm, 90 μ s/cm, 100 μ s/cm, 110 μ s/cm, 120 μ s/cm, 130 μ s/cm, 140 μ s/cm, 150 μ s/cm, and the like. In certain embodiments, the constant voltage is 10V, 15V, 20V, 25V, 30V, 35V, 40V, 45V, 50V, or the like.

In certain embodiments, the solvent comprises pure water.

In certain embodiments, the electrodialysis treatment is performed in one electrodialysis cell. In certain embodiments, step b) of the process of the invention may be repeated in the electrodialysis cell, thereby increasing the separation efficiency. For example, the concentrated compartment liquor may be pumped cyclically into a depletion compartment of an electrodialysis cell in the electrodialysis unit to repeat the electrodialysis step in the electrodialysis cell.

In certain embodiments, the electrodialysis treatment is performed in more than one electrodialysis cell in series. For example, the concentrate compartment supernatant is pumped into the desalination compartments of a two-, three-, four-, or even more-stage electrodialysis device, and step b) of the method according to the invention is repeated, thereby increasing the separation efficiency. In some embodiments, the pressure in the concentrating compartments and the pressure in the desalting compartments are the same between different electrodialysis cells. In some embodiments, the pressure in the concentrating compartments and the pressure in the desalting compartments differ between different electrodialysis cells. In some embodiments, the voltage between the different electrodialysis cells is the same. In some embodiments, the voltage is different between different electrodialysis cells.

The optical isomers resolved using the method of the invention have a purity of greater than 90%, e.g., greater than 91%, greater than 92%, greater than 93%, greater than 94%, greater than 95%, greater than 96%, greater than 97%, greater than 98%, greater than 99%, or even 100%. In certain embodiments, the purity of the optical isomers resolved using the methods of the invention is expressed in terms of ee, which can be measured or calculated by one skilled in the art according to conventional techniques in the art (e.g., HPLC methods), e.g., where a racemate contains A, B two optical isomers, the ee is between a% and B%.

Compared with the prior art, the invention at least has the following advantages:

1. one of the advantages of the invention is that the biocatalysis (such as enzyme catalysis) technology is combined with the electrodialysis technology, the products produced by the enzyme catalysis have different ionization degrees, the electrodialysis technology is used for splitting the optical isomers in the raceme, the reaction condition is mild, and the operation steps are reduced;

2. the electrodialysis technology replaces the conventional extraction means such as the traditional organic solvent extraction, so that the use amount of the organic solvent is greatly reduced, the production cost is reduced, and the environmental pollution is reduced;

3. the extraction rate of the product is improved, the product purity is good, the product can be directly applied, further refining is not needed, the working procedures are reduced, and the cost advantage is achieved;

4. the process is simple and easy to implement, is convenient for automatic operation, improves the operation safety index, and improves the working environment of workers.

Detailed Description

The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto.