Preparation method of homoporous membrane modified by polypeptide chain and separation application of high-added-value chiral amino acid

Abstract

The invention discloses a preparation method of a polypeptide chain modified homo-porous membrane and separation application of high-added-value chiral amino acid, according to the method, a polystyrene block copolymer is used as a membrane forming material, the homo-porous membrane is prepared through a self-assembly and solvent-induced phase separation method, amino active sites are introduced on the homo-porous membrane through a Friedel-Crafts reaction, and the high-added-value chiral amino acid modified homo-porous membrane is obtained. And further initiating anhydride polymerization in the amino acid to form a polypeptide chain by taking the amino group as an initiation site, so as to obtain the homoporous membrane with excellent chiral amino acid identification and separation. According to the method, rapid and stable preparation of the chiral separation layer on the homoporous membrane is realized through ring-opening polymerization of anhydride in amino acid. According to the method, the adopted reaction conditions are mild, the steps are simple, chiral recognition sites can be accurately regulated and controlled through polypeptide chain sequence design, high-selectivity adsorption or rejection of amino acid enantiomers is achieved through the effects of hydrogen bonds, pi-pi and the like, the separation factor reaches 4 or above, and the separation selectivity reaches the high level of similar technologies.

Description

Technical Field

[0001] The present invention belongs to the field of special membrane separation materials, and particularly relates to a preparation method for chiral separation of amino acids by using a polypeptide-modified homogeneous pore membrane. Background Art

[0002] Chiral isomers are two compounds with the same molecular formula but different spatial structures, and most chiral compounds exist in the form of racemates. Chiral compounds are widely used in the fields of medicine, clinical practice, pathology, etc. In modern drug development, more than 50% of drugs are chiral molecules, and their different enantiomers have significant differences in pharmacological activity, metabolic action, and toxicity. In order to obtain enantiomerically pure substances, many methods including column chromatography separation, crystallization separation, membrane separation, etc. have been used for chiral separation. The column chromatography separation method for chiral separation can effectively separate most racemic mixtures. However, this method requires a large amount of organic solvents, and the waste liquid treatment cost is high. In addition, the stationary phase used in column chromatography is expensive, resulting in high costs. The crystallization separation method requires the use of a separating agent to separate the racemate from the racemic solution. However, this method is limited by the type of separating agent and has a limited scope of application. In contrast, membrane separation has the advantages of high energy efficiency, small floor area, simple preparation, and continuous operation, and is particularly suitable for large-scale production.

[0003] Solid chiral membranes are usually formed by the combination of chiral sites and separation membranes, and can be directly used for enantioselective separation. Traditional chiral separation membranes are prepared by adding chiral small molecules or chemically linking chiral sites in the membrane. For the former, the unevenness and small number of chiral sites make it difficult to develop on a large scale. For the latter, although chiral sites are anchored through chemical reactions, the chiral recognition sites on the chiral separation membrane are restricted by the macropores themselves, and chiral substances will undergo non-selective permeation through the macropores, making it difficult to achieve efficient separation of chiral substances. Therefore, there is an urgent need for a chiral membrane that can efficiently separate chiral substances. In traditional ultrafiltration membranes, homogeneous pore membranes have the ability of precise separation and high permeability due to their uniform pore size, high porosity, and unique structure (ACS Nano, 2013(7), 1882). Combining a chiral modification layer with a homogeneous pore substrate membrane is expected to break through the limitation of the "Trade-off" effect between chiral selectivity and permeability. The synergistic effect of the physical sieving of the homogeneous pores themselves and the surface chemical recognition of chiral selective sites can form uniformly distributed chemical selective sites by loading chiral recognition molecules (such as cyclodextrin, protein, chiral ligand) on the surface, which can significantly improve the selectivity of enantiomer separation. In addition, the structure of uniform pores reduces concentration polarization and membrane fouling, reduces pollutant adsorption and pore blockage, and enables the membrane to maintain a high permeation flux, thereby reducing operating pressure and energy consumption. And the method of preparing homogeneous pore membranes based on block copolymers has been widely studied in recent years. Among them, the preparation of homogeneous pore membranes by combining the self-assembly characteristics of block copolymers and phase inversion (Journal of Membrane Science, 2024, 695, 122467) makes the large-scale preparation of homogeneous pore membranes possible, which lays a foundation for the commercial application of homogeneous pore membranes. Modifying homogeneous pore membranes with chiral polypeptide layers can not only achieve the uniform preparation of chiral separation layers, but also the polypeptide chains can precisely regulate chiral recognition sites through sequence design (such as amino acid arrangement, secondary structure), and achieve high-selectivity adsorption or rejection of specific enantiomers through hydrogen bonding, π-π interaction, electrostatic interaction, etc. And desorption and reuse can be achieved through mild conditions (such as pH adjustment), thereby reducing the use cost of chiral separation membranes. In addition, polypeptide materials have good biocompatibility, and the chiral separation homogeneous pore membranes formed by immobilization on the membrane can be used for the chiral separation of high-value biological reagents such as amino acids. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a preparation method for modifying a uniform pore membrane with a polypeptide chain and its application in the separation of high-value-added chiral amino acids. This method uses a polystyrene-based block copolymer to prepare a uniform pore membrane through self-assembly and solvent-induced phase separation, introduces active sites by using an amino cross-linking agent, and finally prepares a chiral separation membrane through surface modification with amino acid anhydride. This method can rapidly prepare a chiral separation layer through the polymerization of amino acid anhydride without doping a chiral selector. The preparation reaction conditions of this method are mild, the steps are simple, and the chiral separation layer can be constructed rapidly. Through the sequence design of the polypeptide chain, the chiral recognition sites are precisely regulated, and combined with the characteristics of the uniform pore size, few defects, and high pore density of the uniform pore membrane, the efficient separation of chiral substances is achieved.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A preparation method for modifying a uniform pore membrane with a polypeptide chain and its application in the separation of high-value-added chiral amino acids, the method comprising the following steps:

[0007] (1) Dissolve the block copolymer in a mixed solvent of dimethylformamide and dioxane, stir evenly to obtain a casting solution, and prepare a uniform pore membrane through the self-assembly of the block copolymer and solution phase inversion; the block copolymer includes a polystyrene hydrophobic segment and a hydrophilic segment of polytetravinylpyridine or polydivinylpyridine. Subsequently, soak it in a 1% iodomethane-ethanol solution for 12 to 24 hours, and soak it in a 0.1 mol / L sodium hydroxide-ethanol solution for 12 to 24 hours.

[0008] (2) Transfer the uniform pore membrane to a mixed solution of an amino cross-linking agent and a catalyst, and use the amino cross-linking agent to undergo an electrophilic substitution reaction with the benzene ring in the block copolymer to uniformly introduce amino active sites on the surface of the uniform pore membrane; the cross-linking agent is a substance that can undergo an electrophilic reaction with the benzene ring, and the conditions for the cross-linking reaction are: reaction time 1 to 6 hours, reaction temperature 20 to 60 °C.

[0009] (3) Wash the cross-linked membrane in an alkaline aqueous solution, and then transfer it to a solution containing N-carboxycyclic anhydride for ring-opening polymerization reaction to obtain a uniform pore membrane modified with a polypeptide on the membrane. The N-carboxycyclic anhydride includes proline anhydride, glutamic acid anhydride, phenylalanine anhydride, etc., and the conditions for the ring-opening polymerization reaction are: reaction time 1 to 20 minutes, reaction temperature 10 to 20 °C, the concentration of N-carboxycyclic anhydride is 10 to 200 mg per milliliter of reaction solvent, and the reaction solvent is an acetonitrile solution containing water.

[0010] Further, the block copolymer is preferably a polystyrene-based block copolymer. Polystyrene-based block copolymer materials are the most commonly used materials for preparing homogeneous pore membranes at present. Using polystyrene as the hydrophobic segment, it has strong incompatibility with the hydrophilic segments P4VP and P2VP, making it easier to achieve microphase separation to form an ordered homogeneous pore structure. At the same time, there is only a benzene ring in polystyrene except for the carbon chain, which is more conducive to the introduction of high-density active sites.

[0011] Further, the content of dioxane in the solvent is 50-90 wt%, and the content of dimethylformamide is 10-50 wt%.

[0012] Further, the crosslinking agent solution is composed of a crosslinking agent and an electrophilic reagent catalyst, and their ratio is: 0.05-0.2 g of the crosslinking agent is dissolved in each milliliter of the catalyst. Preferably, 0.05-0.1 g of the crosslinking agent is dissolved in each milliliter of the catalyst. If the concentration of the crosslinking agent is too low, the degree of crosslinking is low and fewer active sites are introduced.

[0013] Further, the electrophilic reagents include Lewis acids such as aluminum trichloride, zinc chloride, iron trichloride, iron bromide, and trifluoromethanesulfonic acid. The electrophilic reagent can accept the unpaired electrons in the crosslinking agent, making the crosslinking agent positively charged and capable of undergoing an electrophilic reaction with the benzene ring.

[0014] Further, in step (2), the crosslinked membrane needs to be placed in an alkaline solution with a pH of 8-10 to activate the amino active sites on the surface of the homogeneous pore membrane and simultaneously wash away the adsorbed electrophilic reagent.

[0015] Further, the N-amino acid anhydride includes amino acid anhydrides such as proline anhydride, glutamic acid anhydride, and phenylalanine anhydride, and its concentration is preferably 10-200 mg per milliliter of solution.

[0016] Further, the separation targets include various natural amino acids, such as natural high-value-added amino acids like phenylalanine, tryptophan, tyrosine, and glutamic acid.

[0017] A homogeneous pore membrane modified with a polypeptide chain obtained by the above preparation method and its application in separating high-value-added chiral amino acids.

[0018] The beneficial effects of the present invention are as follows:

[0019] (1) The preparation method of the homogeneous pore membrane modified with a polypeptide chain provided by the present invention and its application in separating high-value-added chiral amino acids are applicable to the modification preparation of all homogeneous pore membranes of block copolymers containing benzene rings. It has obvious advantages such as simple preparation steps, fast preparation speed, and wide application range. It has significant value for expanding new applications of homogeneous pore membranes in chiral separation.

[0020] (2) The preparation method of the polypeptide chain modified uniform pore membrane provided by the present invention and its application in the separation of high - value - added chiral amino acids can precisely regulate the structure and composition of chiral recognition sites through polypeptide sequence design, and achieve efficient and precise separation of chiral substances.

[0021] (3) The preparation method of the polypeptide chain modified uniform pore membrane provided by the present invention and its application in the separation of high - value - added chiral amino acids do not require complex operations during the separation process. The chiral separation target is achieved through concentration driving, pressure driving, or a combination of both, with characteristics such as low power consumption and easy continuous production. Moreover, it can improve its permeability while taking into account selectivity, providing the possibility for large - scale application. Brief Description of the Drawings

[0022] Figure 1 It is the infrared spectrum before and after etching and before and after cross - linking of amino active sites in Example 1;

[0023] Figure 2 It is the nuclear magnetic resonance hydrogen spectrum of the block copolymer film before and after etching in Example 1;

[0024] Figure 3 It is the change curve graph of the infrared spectrum of the chiral separation membrane prepared in Example 1 grafted with polypeptide modification layers of different thicknesses;

[0025] Figure 4 It is the electron microscope picture of the influence of introducing amino active site reaction on the surface structure of the uniform pore membrane in Example 2 at different temperatures and times;

[0026] Figure 5 It is the electron microscope picture of constructing a polypeptide modification layer on the surface of the uniform pore membrane in Example 3 at different proline concentrations and different reaction times;

[0027] Figure 6 It is the water contact angle graph of constructing a polypeptide modification layer on the surface of the uniform pore membrane in Example 1 at different proline concentrations and different reaction times;

[0028] Figure 7 It is the separation factor graph of three chiral amino acids by different chiral separation membranes in Example 1;

[0029] Figure 8 It is the schematic diagram of the preparation of the polypeptide - modified uniform pore membrane in Example 2. Detailed Embodiments

[0030] The present invention will be described in detail below according to the drawings and preferred embodiments. The purpose and effect of the present invention will become more apparent. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] Example 1

[0032] (1) Preparation of the homogeneous pore membrane: A PS-b-P4VP block copolymer with a molecular weight of 60,000 g / mol, where the PS accounts for 78 wt%, was dissolved in a mixed solvent of dimethylformamide and dioxane = 9:1 at a concentration of 22 wt%. After stirring and dissolving it into a homogeneous solution, and standing for defoaming, it was blade-coated onto a clean glass plate with a thickness of 150 μm. After 17 s of volatilization, it was immersed in a coagulation bath for phase inversion to form a membrane. After the solvent exchange was complete, the membrane was taken out to obtain the homogeneous pore membrane. Subsequently, it was soaked in a 1% iodomethane-ethanol solution for 24 h and then in a 0.1 mol / L sodium hydroxide-ethanol solution for 12 h to remove the block copolymer in the pores. Among them, Figure 2 The removal of the pyridine peak in the 1H NMR spectrum before and after etching is shown, proving the removal of the block copolymer in the pores.

[0033] (2) Introduction of amino active sites and post-treatment: The membrane prepared above was immersed in a 0.1 g / ml aminoacetaldehyde dimethyl acetal / trifluoromethanesulfonic acid solution and heated at 40 °C for 1 h. After the reaction, the membrane was taken out, rinsed 3 times with ethanol, and then transferred to a sodium hydroxide solution with a pH of 10 and soaked for 60 min. After taking it out, it was placed in deionized water. The reaction equation for the introduction of amino active sites is as follows:

[0034]

[0035] (3) Construction of the polypeptide modification layer: The membrane with surface amino activation was placed in a 50% acetonitrile / water solution containing 25 mg / ml, 50 mg / ml, and 100 mg / ml proline anhydride for 15 min. After the reaction, the membrane was taken out and placed in deionized water to remove the residual monomers and solvents. Thus, the homogeneous pore membrane modified with polypeptide was obtained.

[0036] The structure of the homogeneous pore membrane was characterized by electron microscopy, as Figure 1 shown. The homogeneous pore membrane with the introduced amino cross-linker before the reaction showed a good homogeneous pore structure, while after the surface polymerization reaction of 25 mg / ml, 50 mg / ml, and 100 mg / ml proline anhydride, a polypeptide modification layer grew. The construction of the polypeptide modification layer was proved by infrared characterization, see attachment Figure 3 After the rapid reaction, obvious carbonyl peaks and hydroxyl peaks appeared on the membrane surface, indicating the completion of the preparation of the chiral separation membrane.

[0037] Amino acid chiral separation test:

[0038] The prepared chiral separation membrane was washed with clean water to remove unreacted monomers and solvents on the surface. Subsequently, it was placed in a permeation cell with a 0.005 g / ml L-phenylalanine concentrated solution on one side and only clean water on the other side. The change in the concentration of L-phenylalanine in the clean water pool was monitored at different times to obtain the diffusion rate of L-phenylalanine through the chiral separation membrane. The same method was used to test the diffusion rate of D-phenylalanine. The chiral separation factor was obtained by statistically analyzing the diffusion rates of different chiral amino acids through the homogeneous pore membrane of the chiral separation layer without much peptide modification. See Attachment Figure 7 。

[0039] Example 2

[0040] (1) Preparation of homogeneous pore membrane: A PS-b-P4VP block copolymer with a molecular weight of 150,000 g / mol, where the PS content is 75 wt%, was dissolved in a mixed solvent of dioxane / tetrahydrofuran = 5:5 at a concentration of 25 wt%. After stirring until uniformly dissolved and standing for a period of time, it was coated onto a clean glass plate using a 150-μm-thick doctor blade. After volatilizing for 5 s, it was immersed in water for phase inversion to form a membrane. After the solvent exchange was complete, the formed film was taken out and dried to obtain a homogeneous pore membrane, and the surface homogeneous pore structure was characterized by electron microscopy. Subsequently, it was soaked in a 1% iodomethane-ethanol solution for 24 h and then in a 0.1 mol / L sodium hydroxide-ethanol solution for 24 h to remove the block segments in the pores.

[0041] (2) Introduction of amino active sites and post-treatment: The membrane prepared above was immersed in a 0.05 g / ml aminoacetaldehyde dimethyl acetal / trifluoromethanesulfonic acid solution and heated at 40 °C for 3 h. After the reaction, the membrane was taken out, rinsed 3 times with ethanol, and then transferred to a sodium hydroxide solution with a pH of 10 and soaked for 60 min. After taking it out, it was placed in deionized water.

[0042] (3) Construction of the polypeptide modification layer: The membrane with activated surface amino groups was placed in a 20% acetonitrile / water solution containing 25 mg / ml, 50 mg / ml, and 100 mg / ml proline anhydride for 15 min. After the reaction, the membrane was taken out and placed in deionized water to remove the remaining monomers and solvents. Thus, the homogeneous pore membrane modified with polypeptide was obtained.

[0043] The structure of the homogeneous pore membrane before and after the reaction was characterized by electron microscopy. As Figure 4 shown, the homogeneous pore membrane with an introduced amino cross-linking agent before the reaction exhibited a good homogeneous pore structure, while a polypeptide modification layer grew after the surface polymerization reaction with 25 mg / ml, 50 mg / ml, and 100 mg / ml proline anhydride. The construction of the polypeptide modification layer was proved by infrared spectroscopy. Obvious carbonyl peaks and hydroxyl peaks appeared on the membrane surface after the rapid reaction, indicating the completion of the preparation of the chiral separation membrane.

[0044] Amino acid chiral separation test:

[0045] The prepared chiral separation membrane was washed with clean water to remove the unreacted monomers and solvents on the surface. Subsequently, it was placed in a permeation cell with a 0.001 g / ml L-tryptophan concentrated solution on one side and only clean water on the other side. After monitoring the change in the L-tryptophan concentration in the clean water pool at different times, the diffusion rate of L-phenylalanine through the chiral separation membrane was obtained. The same method was used to test the diffusion rate of D-tryptophan. The chiral separation factor of the membrane was obtained by statistically analyzing the diffusion rates of different chiral amino acids through the chiral separation membrane.

[0046] Example 3

[0047] (1) Preparation of the homogeneous pore membrane: A PS-b-P4VP block copolymer with a molecular weight of 125,000 g / mol, where the PS content is 86 wt%, was dissolved in a mixed solvent of 1,4-dioxane / dimethylformamide = 8:2 at a concentration of 25 wt%. After stirring until uniformly dissolved and standing for a period of time, it was coated onto a clean glass plate using a 150-μm-thick doctor blade. After volatilizing for 25 s, it was immersed in water for phase inversion to form a membrane. After the solvent exchange was complete, the formed film was taken out and air-dried to obtain the homogeneous pore membrane. Subsequently, it was soaked in a 1% methyl iodide-ethanol solution for 24 h and then in a 0.1 mol / L sodium hydroxide-ethanol solution for 24 h to remove the block copolymer in the pores.

[0048] (2) Introduction of amino active sites and post-treatment: The membrane prepared above was immersed in a 0.05 g / ml solution of aminoacetaldehyde dimethyl acetal / trifluoromethanesulfonic acid and heated at 60 °C for 3 h. After the reaction, the membrane was taken out, rinsed three times with ethanol, and then transferred to a sodium hydroxide solution with a pH of 10 and soaked for 60 min. After taking it out, it was placed in deionized water.

[0049] (3) Construction of the polypeptide modification layer: The membrane with activated surface amino groups was placed in a 20% acetonitrile / water solution containing 25 mg / ml, 50 mg / ml, and 100 mg / ml of proline anhydride for 15 min. After the reaction, the membrane was taken out and placed in deionized water to remove the residual monomers and solvents. Thus, the homogeneous pore membrane modified with polypeptide was obtained.

[0050] The structure of the homogeneous pore membrane before and after the reaction was characterized by electron microscopy. The homogeneous pore membrane with an amino cross-linking agent before the reaction showed a good homogeneous pore structure, while a polypeptide modification layer grew after the surface polymerization reaction with 25 mg / ml, 50 mg / ml, and 100 mg / ml of proline anhydride. The construction of the polypeptide modification layer was proved by infrared spectroscopy. After the rapid reaction, obvious carbonyl peaks and hydroxyl peaks appeared on the membrane surface, indicating the completion of the preparation of the chiral separation membrane.

[0051] Amino acid chiral separation test:

[0052] The prepared chiral separation membrane was washed with clean water to remove unreacted monomers and solvents on the surface. Subsequently, it was placed in a permeation cell with a 0.001 g / ml L-tyrosine concentrated solution on one side and only clean water on the other side. After monitoring for different times, the change in the L-tyrosine concentration in the clean water tank was obtained to get the diffusion rate of L-tyrosine through the chiral separation membrane. The same method was used to test the diffusion rate of D-tyrosine. The chiral separation factor was obtained by statistically analyzing the diffusion rates of different chiral amino acids through the chiral separation membrane.

[0053] Example 4

[0054] (1) Preparation of the homogeneous pore membrane: A PS-b-P2VP block copolymer with a molecular weight of 100,000 g / mol, where the PS content is 81 wt%, was dissolved in a mixed solvent of 1,4-dioxane and dimethylformamide = 9:1 at a concentration of 22 wt%. After stirring until uniformly dissolved and standing for a period of time, it was coated onto a clean glass plate using a 150-μm-thick doctor blade. After volatilizing for 10 s, it was immersed in water for phase inversion to form a membrane. After the solvent exchange was complete, the formed thin film was taken out and dried to obtain the homogeneous pore membrane. Its surface homogeneous pore structure was characterized by electron microscopy. Subsequently, it was soaked in a 1% iodomethane-ethanol solution for 24 h and then in a 0.1 mol / L sodium hydroxide-ethanol solution for 24 h to remove the block segments in the pores.

[0055] (2) Introduction of amino active sites and post-treatment: The membrane prepared above was immersed in a 0.15 g / ml aminoacetaldehyde dimethyl acetal / trifluoromethanesulfonic acid solution and heated at 50 °C for 3 h. After the reaction, the membrane was taken out, rinsed 3 times with ethanol, and then transferred to a sodium hydroxide solution with a pH of 10 and soaked for 60 min. After taking it out, it was placed in deionized water.

[0056] (3) Construction of the polypeptide modification layer: The membrane with activated surface amino groups was placed in a 20% acetonitrile / aqueous solution containing 25 mg / ml, 50 mg / ml, and 100 mg / ml proline anhydride for 15 min. After the reaction, the membrane was taken out and placed in deionized water to remove residual monomers and solvents. Thus, the homogeneous pore membrane modified with polypeptide was obtained.

[0057] The structure of the homogeneous pore membrane before and after the reaction was characterized by electron microscopy. The homogeneous pore membrane with an amino cross-linking agent introduced before the reaction showed a good homogeneous pore structure, while a polypeptide modification layer grew after the surface polymerization reaction with 25 mg / ml, 50 mg / ml, and 100 mg / ml proline anhydride. The construction of the polypeptide modification layer was proved by infrared spectroscopy, and obvious carbonyl peaks and hydroxyl peaks appeared on the membrane surface, indicating the completion of the preparation of the chiral separation membrane.

[0058] Amino acid chiral separation test:

[0059] The prepared chiral separation membrane was washed with clean water to remove unreacted monomers and solvents on the surface. Subsequently, it was placed in a permeation cell with a 0.005 g / ml L-phenylalanine concentrated solution on one side and only clean water on the other side. After monitoring the changes in the concentration of L-phenylalanine in the clean water pool at different times, the diffusion rate of L-phenylalanine through the chiral separation membrane was obtained. The same method was used to test the diffusion rate of D-phenylalanine. The chiral separation factor was obtained by statistically analyzing the diffusion rates of different chiral amino acids through the chiral separation membrane.

[0060] Example 5

[0061] (1) Preparation of the homogeneous pore membrane: A PS-b-P4VP block copolymer with a molecular weight of 156,000 g / mol, where the PS content is 85 wt%, was dissolved in a mixed solvent of dimethylformamide / 1,4-dioxane = 3:7 at a concentration of 22 wt%. After stirring until uniformly dissolved and standing for a period of time, it was coated onto a clean glass plate using a 150-μm-thick doctor blade. After volatilizing for 1 s, it was immersed in water for phase inversion to form a membrane. After the solvent exchange was complete, the formed thin film was taken out and dried to obtain the homogeneous pore membrane. The surface homogeneous pore structure was characterized by electron microscopy. Subsequently, it was soaked in a 1% iodomethane-ethanol solution for 24 h and then in a 0.1 mol / L sodium hydroxide-ethanol solution for 24 h to remove the block segments in the pores.

[0062] (2) Introduction of amino active sites and post-treatment: The membrane prepared above was immersed in a 0.1 g / ml aminoacetaldehyde dimethyl acetal / trifluoromethanesulfonic acid solution and heated at 40 °C for 3 h. After the reaction, the membrane was taken out, rinsed 3 times with ethanol, and then transferred to a sodium hydroxide solution with a pH of 10 and soaked for 60 min. After taking it out, it was placed in deionized water.

[0063] (3) Construction of the polypeptide modification layer: The membrane with activated surface amino groups was placed in a 20% acetonitrile / aqueous solution containing 25 mg / ml, 50 mg / ml, and 100 mg / ml proline anhydride for 15 min. After the reaction, the membrane was taken out and placed in deionized water to remove the remaining monomers and solvents. Thus, the homogeneous pore membrane modified with polypeptide was obtained.

[0064] The structure of the homogeneous pore membrane before and after the reaction was characterized by electron microscopy. The homogeneous pore membrane with an amino cross-linking agent introduced before the reaction showed a good homogeneous pore structure, while a polypeptide modification layer grew after the surface polymerization reaction with 25 mg / ml, 50 mg / ml, and 100 mg / ml glutamic anhydride. The construction of the polypeptide modification layer was proved by infrared spectroscopy, and obvious carbonyl peaks and hydroxyl peaks appeared on the membrane surface, indicating the completion of the preparation of the chiral separation membrane.

[0065] Amino acid chiral separation test:

[0066] The prepared chiral separation membrane was washed with clean water to remove the unreacted monomers and solvents on the surface. Subsequently, it was placed in a permeation cell with a 0.001 g / ml L-tyrosine concentrated solution on one side and only clean water on the other side. After monitoring for different times, the change in the L-tyrosine concentration in the clean water pool was obtained to get the diffusion rate of L-phenylalanine through the chiral separation membrane. The same method was used to test the diffusion rate of D-tyrosine. The chiral separation factor was obtained by statistically analyzing the diffusion rates of different chiral amino acids through the chiral separation membrane.

[0067] Those of ordinary skill in the art can understand that the above are only preferred examples of the invention and are not used to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A preparation method for modifying a uniform pore membrane through a polypeptide chain and its application in the separation of high-value-added chiral amino acids, characterized in that, The method comprises the following steps: S1: Dissolve the block copolymer in a mixed solvent of dimethylformamide and dioxane, stir evenly to obtain a casting solution, and prepare a homogeneous pore membrane through self-assembly of the block copolymer and solution phase inversion; the block copolymer includes a polystyrene hydrophobic chain segment and a hydrophilic chain segment of polytetravinylpyridine or polydivinylpyridine. Subsequently, soak it in a 1% methyl iodide-ethanol solution for 12 to 24 h, and soak it in a 0.1 mol / L sodium hydroxide-ethanol solution for 12 to 24 h; S2: Transfer the homogeneous pore membrane to a mixed solution of an amino cross-linking agent and a catalyst, and use the amino cross-linking agent to undergo an electrophilic substitution reaction with the benzene ring in the block copolymer to uniformly introduce amino active sites on the surface of the homogeneous pore membrane; the cross-linking agent is a substance capable of undergoing an electrophilic reaction with the benzene ring, and the conditions for the cross-linking reaction are: reaction time 1 to 6 h, reaction temperature 20 to 60 °C; S3: Wash the cross-linked membrane in an alkaline aqueous solution, and then transfer it to a solution containing N-carboxy anhydride for ring-opening polymerization reaction to obtain a homogeneous pore membrane modified with polypeptides on the membrane. The N-carboxy anhydride includes proline anhydride, glutamic anhydride, phenylalanine anhydride, etc., and the conditions for the ring-opening polymerization reaction are: reaction time 1 to 20 min, reaction temperature 10 to 20 °C, the concentration of N-carboxy anhydride is 10 to 200 mg per milliliter of reaction solvent, and the reaction solvent is an acetonitrile solution containing water.

2. The preparation method of the uniformly porous membrane modified by a polypeptide chain and the separation application of high-value-added chiral amino acids according to claim 1, wherein, The molecular weight range of the block copolymer is 60,000 to 150,000 g / mol, and the volume fraction of polystyrene accounts for 72 to 90%.

3. The preparation method of the homogeneous pore membrane modified by polypeptide chain according to claim 1 and the separation application of high-value-added chiral amino acids, characterized in that, The cross-linking agent should be an alkylating reagent containing amino, including dimethoxymethane acetaldehydeamine, diethoxymethane acetaldehydeamine, dimethoxymethane 2-aminopropionaldehyde, and preferably dimethoxymethane acetaldehydeamine.

4. The preparation method of the homogeneous pore membrane modified by polypeptide chain according to claim 1 and the separation application of high-value-added chiral amino acids, characterized in that, The cross-linking reaction solution is composed of a cross-linking agent and a trifluoromethanesulfonic acid catalyst, and their ratio is that 0.05 to 0.2 g of the cross-linking agent is dissolved in each milliliter of the trifluoromethanesulfonic acid catalyst.

5. The preparation method of the uniform pore membrane modified by polypeptide chain and the separation application of high-value-added chiral amino acids according to claim 1, characterized in that, In step (3), the cross-linked membrane is washed in a solution with pH = 8 to 10 for 10 to 60 minutes to completely remove the catalyst and unreacted cross-linking agent.

6. The preparation method of modifying a uniform pore membrane through a polypeptide chain and the separation application of high-value-added chiral amino acids according to claim 1, characterized in that, The reaction substance should be a single optically active N-carboxy anhydride.

7. The preparation method of the homogeneous pore membrane modified by polypeptide chain according to claim 4 and the separation application of high-value-added chiral amino acids, characterized in that, The surface modification layer is obtained by ring-opening polymerization of one or more of the N-carboxy anhydrides.

8. The preparation method of the uniformly porous membrane modified by a polypeptide chain and the separation application of high-value-added chiral amino acids according to claim 1, characterized in that, The substance to be separated is suitable for chiral amino acids, and the separation process can be driven by pressure, concentration, or a combination of both.

9. A preparation method for preparing a homogeneous pore membrane modified with polypeptide chains and an application for separating high-value-added chiral amino acids by the preparation method according to claims 1 to 8.

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