A method for separating mixed amino acids using an ion rectification system

Abstract

The application discloses a method for separating mixed amino acids by using an ion rectification system, wherein the pH of a mixed amino acid solution is regulated according to the isoelectric points of two amino acids in the mixed amino acids, the overall charge type ions of the two amino acids in the mixed amino acids are determined, and then the selective coefficients of the two amino acids are gradually improved by using corresponding ion rectification systems. The method can realize high-selectivity separation of various types of mixed amino acids, especially high-selectivity separation of mixed amino acids with similar isoelectric points, similar structures, similar molecular weights and / or the same charge amounts, and provides an innovative method for separation of mixed amino acids, which is expected to shorten the subsequent separation and purification process route in the production process of amino acids, reduce the production cost of amino acids and improve the product quality of amino acids.

Description

Technical Field

[0001] This invention belongs to the field of electro-driven membrane separation, specifically relating to a method for separating mixed amino acids with similar isoelectric points, structures, molecular weights, and / or charges. Background Technology

[0002] Amino acids are important chemical raw materials with extensive applications in pharmaceuticals, cosmetics, food, and animal feed. Currently, amino acids can be obtained through the hydrolysis of natural proteins or through bioengineering fermentation, but this often results in a mixture of amino acids, rather than obtaining a specific pure amino acid in one step. With the development of related industries and bioengineering technology, the demand for amino acids is increasing, and the requirements for their purity are also becoming more stringent. How to achieve the precise separation of mixed amino acids is a crucial problem that modern chemical industry urgently needs to solve.

[0003] For mixed amino acid solutions, the most commonly used methods both domestically and internationally include precipitation, extraction, ion exchange, and electrodialysis. While all these processes can purify and separate mixed amino acids, they still face numerous challenges due to inherent technological barriers. Precipitation requires the addition of specific precipitants or adjustment of the solution pH to the isoelectric point of the amino acids to induce precipitation. Residual precipitants affect product purity and are difficult to recover; furthermore, the isoelectric points of the amino acids to be separated cannot be close. Extraction faces issues such as the impact of non-toxic or low-toxic extractant residues on product quality and emulsification during extraction. Ion exchange, by adjusting the pH of the feed solution and utilizing the differences in the dissociation constants (pK) and isoelectric points (pI) between amino acids, allows for separation and purification based on the varying adsorption capacities of ion exchange resins. However, this process requires the treatment of large quantities of resin and the use of significant amounts of acid or alkali to elute the amino acids from the separation column, making the operation cumbersome. Individual ion exchange units cannot operate continuously; they can only separate target ions through intermittent feeding and washing. While continuous material processing can be achieved by connecting ion exchange units in series or parallel, this also prolongs the engineering process, and the coupling and matching of each unit during operation makes the process extremely complex. Generally, electrodialysis requires adjusting the pH of the amino acid mixture solution so that cations are predominantly one amino acid and anions are predominantly another. Under the influence of a DC electric field, cations migrate through the cation exchange membrane to the cathode, and anions migrate through the anion exchange membrane to the anode, thus achieving separation. However, conventional electrodialysis cannot achieve exponential scaling of the selectivity coefficient. Due to the large molecular weight and high mass transfer resistance of amino acid ions, the selectivity coefficient of mixed amino acids in conventional electrodialysis is often low. Selective electrodialysis, an electrically driven membrane separation process, can be used for the separation of mixed amino acids. Based on the differences in the physicochemical properties of different amino acid ions, such as charge, hydration energy, and ion hydration radius, specialized functional membranes, such as monovalent ion selective membranes and electrofiltration membranes, are used. These membranes utilize the specific response between amino acid ions and the functional membrane, and different amino acid ions migrate at different rates within the membrane (generally, smaller molecular weight and simpler structure amino acid ions migrate faster). Driven by an electric field, and using functional membranes in a specific arrangement, efficient separation of mixed amino acids can be achieved. Selective electrodialysis is widely used in organic acid production, organic wastewater treatment, and green chemical production processes. Selective electrodialysis uses a flow-through feed and discharge mode, where the material flows within the selective electrodialysis membrane stack. Its processing efficiency depends on the residence time of the material in the electrodialysis unit and the external electric field. The flow-through feed mode allows a single selective electrodialysis unit to operate under continuous, intermittent, and semi-intermittent process conditions.However, due to the basic operating mechanism of the electrodialysis process, electrodialysis typically employs a combination of cation-specific separation membranes and anion-specific separation membranes. These two types of membranes are stacked to form a single membrane unit, and by repeatedly stacking these units, the material throughput can be increased. Therefore, in the electrodialysis process, the separation performance of specific ions still depends on the sieving characteristics of the functional membrane itself, and the suboptimal sieving performance of the functional membrane also limits the target ion separation efficiency.

[0004] Existing amino acid separation and purification routes often employ the synergistic coupling of multiple technical units, resulting in long technical routes, complex processes, and low integration, which are common problems in existing production processes.

[0005] Ion distillation is a novel electro-driven membrane separation technology that arranges multiple ion-exchange membranes of the same type on the same side. Due to differences in physicochemical properties between different ions, such as hydrated ionic radius, hydration energy, and charge, the migration rates of mixed ions in the membrane differ. Membranes can be used to partially separate these different ions, which is the separation mechanism followed by traditional selective electrodialysis. However, for amino acid ions with similar isoelectric points, structures, molecular weights, and / or charges, their migration rate differences in the membrane phase are minimal, requiring external coupling through hundreds or even thousands of selective electrodialysis units. Ion distillation technology possesses a series amplification effect in ion selectivity, and leveraging this advantage, it holds promise for the fine separation of complex mixed amino acid systems. Currently, ion distillation mainly focuses on the separation of mixed metal ion systems, especially those generated during the resource recovery process of salt lakes, and has not yet been applied to the separation of mixed organic acid systems, particularly mixed amino acid systems with similar isoelectric points, structures, molecular weights, and / or charges. Summary of the Invention

[0006] To avoid the shortcomings of the aforementioned mixed amino acid separation technologies, this invention provides a method for separating mixed amino acids using an ion distillation system. By constructing an ion distillation system, based on the relationship between the isoelectric point of amino acids and the pH of the solution, the multi-stage sieving mechanism of amino acid ions in a functional membrane, and the series amplification effect of the ion selectivity coefficient, the method achieves the goal of finely sieving amino acids from a mixed amino acid solution. This method can achieve the separation of various types of mixed amino acids, especially the fine sieving of mixed amino acids with similar isoelectric points, structures, molecular weights, and / or charges that cannot be achieved by existing electrodialysis methods.

[0007] Due to the difficulty in separating mixed amino acids with similar isoelectric points, structures, molecular weights, and / or charges, traditional separation systems often select amino acid separation systems with significantly different isoelectric points, molecular weights, structures, and charges. Limited by the basic operating mechanism of electrodialysis, electrodialysis typically uses a combination of special cation-separation membranes and special anion-separation membranes, stacking the two membranes to form a membrane unit. Repeatedly stacking these membrane units can increase the material throughput. This invention breaks the basic operating mechanism of traditional electrodialysis, arranging ion-exchange membranes according to the principle of "like on the same side." Combined with the solution pH conditions, the main charge type ions of the mixed amino acids are determined, and n "like" ion-exchange membranes capable of screening and transporting the main charge type amino acid ions are sequentially stacked. By utilizing the differences in migration rates of different amino acid ions, and ultimately performing n-stage selective separation, the selectivity coefficients between different amino acid ions are amplified exponentially, thereby achieving efficient separation of various types of mixed amino acids in the ion distillation system. In particular, it achieves efficient separation of mixed amino acids with similar isoelectric points, structures, molecular weights, and / or charges, reaching the highest amino acid selectivity coefficient reported to date for a single membrane separation unit for mixed amino acid systems with similar isoelectric points, structures, molecular weights, and / or charges.

[0008] To solve the technical problem, the present invention adopts the following technical solution:

[0009] A method for separating mixed amino acids using an ion distillation system is characterized by: adjusting the pH of the mixed amino acid solution according to the isoelectric points of the two amino acids in the mixture, determining the overall charge type ions of the two amino acids in the mixture, and then using a corresponding ion distillation system to achieve a stepwise increase in the selectivity coefficient of the two amino acids.

[0010] The method of the present invention is applicable to both mixed amino acids with different isoelectric points and the separation of mixed amino acids with similar isoelectric points. For example, when the difference in isoelectric points between two amino acids is not greater than a certain set value a (e.g., a is set to any value between 0.6 and 1.2), the two amino acids can be considered to have similar isoelectric points; when the difference in isoelectric points between two amino acids is greater than the set value a, the two amino acids can be considered to have different isoelectric points.

[0011] Amino acids exhibit different charge states under different pH conditions: when the pH of the solution is lower than the isoelectric point (pI) of that type of amino acid, the amino acid of that type is positively charged as a whole (i.e., the number of positively charged molecules is greater than the number of negatively charged molecules); when the pH of the solution is higher than the isoelectric point of that type of amino acid, the amino acid of that type is negatively charged as a whole (i.e., the number of negatively charged molecules is greater than the number of positively charged molecules). Based on the difference in isoelectric points between two amino acids, the pH of a mixed amino acid mixture can be adjusted: when the isoelectric points of the two amino acids are not similar, the pH is adjusted to make the overall charge types of the two amino acids different (one is positively charged and the other is negatively charged); when the isoelectric points of the two amino acids are similar, the pH is adjusted to make the overall charge types of the two amino acids the same or one of them electrically neutral. Based on the overall charge type of the two amino acids in the mixed amino acid mixture after pH adjustment, an ion distillation system is selected: when the two amino acids have different overall charge types (one is positively charged and the other is negatively charged), an ion-co-distillation system is used; when one amino acid in the mixed amino acid mixture is positively charged and the other is either neutral or positively charged, a cation distillation system or an ion-co-distillation system is used; when one amino acid in the mixed amino acid mixture is negatively charged and the other is either neutral or negatively charged, an anion distillation system or an ion-co-distillation system is used. Amino acid ions migrate across the membrane, and due to differences in their migration rates, the selectivity is further amplified by passing through n stages of distillation chambers, based on the main charged ion ratio adjusted by pH.

[0012] Furthermore, the method for separating mixed amino acids using an ion distillation system specifically involves setting the isoelectric points of amino acid A and amino acid B in the mixed amino acids to pI0 and pI0, respectively. A With pI B ;

[0013] If pI B -pI A >a (that is, when the isoelectric points of the two amino acids are not similar), the following method is used to separate the mixed amino acids:

[0014] First, adjust the pH of the mixed amino acid solution to pI. A <pH<pI B This results in amino acid A being negatively charged as a whole and amino acid B being positively charged as a whole in the mixed amino acid solution.

[0015] An ion-coordinated distillation system is set up. A mixed amino acid solution to be treated is added to the feed chamber. A strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each cation distillation chamber and each anion distillation chamber. Under the drive of an electric field, positively charged amino acid A and positively charged amino acid B pass through the feed chamber sequentially through each stage of the cation exchange membrane. Based on the difference in migration rates between amino acid A and amino acid B, the selectivity coefficient of the two positively charged amino acids increases progressively in each stage of the cation distillation chamber. Simultaneously, under the drive of an electric field, negatively charged amino acid A and negatively charged amino acid B pass through the feed chamber sequentially through each stage of the anion exchange membrane. Based on the difference in migration rates between amino acid A and amino acid B, the selectivity coefficient of the two negatively charged amino acids increases progressively in each stage of the anion distillation chamber. This achieves the separation of the two amino acids in the mixed amino acid solution.

[0016] If 0 < pI B -pI A ≤a (that is, when the isoelectric points of the two amino acids are similar), the mixed amino acids can be separated using either method one or method two as follows:

[0017] Method 1:

[0018] First, adjust the pH of the mixed amino acid solution to pH ≤ pI. A This results in amino acid A in the mixed amino acid solution being either electrically neutral or positively charged as a whole, while amino acid B is positively charged as a whole.

[0019] A cation distillation system is set up, and the mixed amino acid solution to be treated is added to the feed chamber. A strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each cation distillation chamber and each anion retention chamber. Under the drive of an electric field, positively charged amino acid A and positively charged amino acid B pass through the cation exchange membranes of each stage from the feed chamber. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two positively charged amino acids increases step by step in each cation distillation chamber, thereby achieving the separation of the two amino acids in the mixed amino acid solution.

[0020] Alternatively, an ion-coordinated distillation system can be set up. The mixed amino acid solution to be treated is added to the feed chamber, a strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each cation distillation chamber and each anion distillation chamber. Under the drive of an electric field, positively charged amino acid A and positively charged amino acid B pass through the feed chamber stepwise through each stage of the cation exchange membrane. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two positively charged amino acids increases stepwise in each stage of the cation distillation chamber. Simultaneously, under the drive of an electric field, negatively charged amino acid A and negatively charged amino acid B pass through the feed chamber stepwise through each stage of the anion exchange membrane. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two negatively charged amino acids increases stepwise in each stage of the anion distillation chamber. Thus, the separation of the two amino acids in the mixed amino acid solution is achieved.

[0021] Method 2:

[0022] First, adjust the pH of the mixed amino acid solution to pH ≥ pI. B This results in amino acid A in the mixed amino acid solution being negatively charged as a whole, while amino acid B is either electrically neutral or negatively charged as a whole.

[0023] An anion distillation system is set up. The mixed amino acid solution to be treated is added to the feed chamber, a strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each anion distillation chamber and each cation retention chamber. Under the drive of an electric field, negatively charged amino acid A and negatively charged amino acid B pass through each anion exchange membrane step by step from the feed chamber. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two negatively charged amino acids increases step by step in each anion distillation chamber, thereby achieving the separation of the two amino acids in the mixed amino acid solution.

[0024] Alternatively, an ion-coordinated distillation system can be set up. The mixed amino acid solution to be treated is added to the feed chamber, a strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each cation distillation chamber and each anion distillation chamber. Under the drive of an electric field, positively charged amino acid A and positively charged amino acid B pass through the feed chamber stepwise through each stage of the cation exchange membrane. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two positively charged amino acids increases stepwise in each stage of the cation distillation chamber. Simultaneously, under the drive of an electric field, negatively charged amino acid A and negatively charged amino acid B pass through the feed chamber stepwise through each stage of the anion exchange membrane. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two negatively charged amino acids increases stepwise in each stage of the anion distillation chamber. Thus, the separation of the two amino acids in the mixed amino acid solution is achieved.

[0025] Furthermore, when 0 < pI B -pI AWhen the pH is ≤a (that is, when the isoelectric points of the two amino acids are similar), the pH of the mixed amino acid solution is adjusted according to the relationship between the distribution of amino acid ions and pH, so that amino acid A and amino acid B have the same charge type as a whole, while the ratio of the two amino acid ions with the same charge type is the largest. The pH at this time is the optimal operating pH. Under this condition, the selectivity coefficient of the mixed amino acid ions can be improved.

[0026] Furthermore, the acid or base used to adjust the pH of the mixed amino acid solution is an inorganic acid or inorganic base.

[0027] Furthermore, the ion distillation system used can be either a symmetrical or asymmetrical structure, meaning that the ratio between the number of films used for cation sieving (n1) and the number of films used for anion sieving (n2) can be freely combined.

[0028] Furthermore, the ion distillation system used has two or more distillation stages, and the number of ion distillation stages can be freely increased or decreased according to the composition of the system being processed and the processing objectives.

[0029] Furthermore, the membranes used in the ion distillation system can be selected as needed. Optional membranes include, but are not limited to, monovalent and polyvalent ion membranes, electrofiltration membranes, conventional ion exchange membranes, bipolar membranes, alkaline membranes, proton exchange membranes, alloy membranes, and heterogeneous membranes.

[0030] Furthermore, the end-capping membrane used in the ion distillation system can be selected as needed, and the available membranes include, but are not limited to, ion exchange membranes, bipolar membranes, alkaline membranes, proton exchange membranes, alloy membranes, heterogeneous membranes, etc.

[0031] Specifically, the amino acids include, but are not limited to, 20 common amino acids involved in human life activities, such as glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), phenylalanine (Phe), serine (Ser), and proline (Pro). Taking a mixed system composed of glycine (Gly) and alanine (Ala) as an example, the structures of glycine (Gly) and alanine (Ala) are shown below:

[0032]

[0033] Structurally, glycine (Gly) and alanine (Ala) differ only in their R groups: Glycine has a -H R group, while Ala has a methyl (-CH2) R group. In terms of molecular weight, glycine (Gly) has a molecular weight of 75.067, and Ala has a molecular weight of 89.093, differing only by the molecular weight of the methyl (-CH2) group. In aqueous solution, glycine (Gly) and alanine (Ala) undergo the following dissociation:

[0034] pK1 = 2.34

[0035] pK2 = 9.60

[0036] pK1 = 2.35

[0037] pK2 = 9.87

[0038] Where pI represents the isoelectric point of the amino acid, pK1 represents the carboxyl dissociation constant of the amino acid, and pK2 represents the amino dissociation constant of the amino acid. Regarding isoelectric points, glycine (Gly) has an isoelectric point of 5.97, and alanine (Ala) has an isoelectric point of 6.00, which are very close. When both glycine (Gly) and alanine (Ala) are positively charged, they are both mono-positively charged; when both glycine (Gly) and alanine (Ala) are negatively charged, they are both mono-negatively charged. According to the relationship between the ion distribution of the two amino acids and pH (method referred to in the Journal of Membrane Science 498(2016)48–56), at pH 9.735, both glycine and alanine are negatively charged overall, with the proportion of negatively charged ions in glycine being 0.5771 and in alanine 0.4229, and the difference in the proportion of negatively charged ions between the two reaches a maximum of 0.1542.

[0039] The ion distillation system of the present invention includes a cation distillation system, an anion distillation system, and an ion-coordinated distillation system.

[0040] The structure of the cation distillation system is described in patent CN 113663519A: it includes a cation distillation device, a solution-assisted circulation system, and a current power supply system. The cation distillation device consists of at least one set of cation distillation units encapsulated between the anode and cathode plates. Each cation distillation unit is a membrane unit composed of one or more anion exchange membranes and at least two special cation selective membranes stacked sequentially according to the "same type, same side" principle, with a flow channel mesh and sealing gaskets added. In the cation distillation unit, the anion exchange membranes are stacked first, followed by the special cation selective membranes, with the anion exchange membranes close to the anode plate and the special cation selective membranes close to the cathode plate. One or more anion retention chambers are formed between adjacent anion exchange membranes; at least two stages of cation distillation chambers are formed between adjacent special cation selective membranes; and a feed chamber is formed between the anion exchange membranes and the special cation selective membranes. A sealing diaphragm is provided between the anode plate, the cathode plate and the cation distillation unit; an anode chamber is formed between the anode plate and the sealing diaphragm, and a cathode chamber is formed between the cathode plate and the sealing diaphragm; an anion retention chamber is formed between the sealing diaphragm near the anode plate and the adjacent anion exchange membrane, and a cation distillation chamber is formed between the sealing diaphragm near the cathode plate and the adjacent special cation selective membrane.

[0041] The anion distillation system described in patent CN 113663517 A includes anion distillation devices, a solution-assisted circulation system, and a current-powered system. The anion distillation device consists of at least one set of anion distillation units encapsulated between an anode and a cathode plate. Each anion distillation unit is a membrane unit composed of one or more cation exchange membranes and at least two special anion-selective membranes stacked sequentially according to the "same type, same side" principle, with a flow channel mesh and a sealing gasket added. In the anion distillation unit, the special anion-selective membranes are stacked first, followed by the cation exchange membranes, with the special anion-selective membranes close to the anode plate and the cation exchange membranes close to the cathode plate. At least two stages of anion distillation chambers are formed between adjacent special anion-selective membranes; one or more cation retention chambers are formed between adjacent cation exchange membranes; and a feed chamber is formed between the special anion-selective membranes and the cation exchange membranes. A sealing diaphragm is provided between the anode plate, the cathode plate and the anion distillation unit; an anode chamber is formed between the anode plate and the sealing diaphragm, and a cathode chamber is formed between the cathode plate and the sealing diaphragm; an anion distillation chamber is formed between the sealing diaphragm near the anode plate and the adjacent special anion selective membrane, and a cation retention chamber is formed between the sealing diaphragm near the cathode plate and the adjacent cation exchange membrane.

[0042] The ion-coordinated distillation system described in patent CN 113663518 A includes an ion-coordinated distillation device, a solution-assisted circulation system, and a current-powered system. The ion-coordinated distillation device consists of at least one set of ion-coordinated distillation units encapsulated between an anode and a cathode plate. Each ion-coordinated distillation unit is a membrane unit composed of one or more special cation-selective membranes and one or more special anion-selective membranes stacked sequentially according to the "same type, same side" principle, with a flow channel mesh and a sealing gasket added. In the ion-coordinated distillation unit, the special anion-selective membranes are stacked first, followed by the special cation-selective membranes, with the special anion-selective membranes close to the anode plate and the special cation-selective membranes close to the cathode plate. One or more anion distillation chambers are formed between adjacent special anion-selective membranes; one or more cation distillation chambers are formed between adjacent special cation-selective membranes; and a feed chamber is formed between the special anion-selective membranes and the special cation-selective membranes. A sealing diaphragm is provided between the anode plate, the cathode plate and the ion co-distillation unit; an anode chamber is formed between the anode plate and the sealing diaphragm, and a cathode chamber is formed between the cathode plate and the sealing diaphragm; an anion distillation chamber is formed between the sealing diaphragm near the anode plate and the adjacent special anion selective membrane, and a cation distillation chamber is formed between the sealing diaphragm near the cathode plate and the adjacent special cation selective membrane.

[0043] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0044] This invention achieves effective separation of different amino acid molecules by controlling the pH of a mixed amino acid solution to induce charge conversion in the mixed amino acid molecules and utilizing the series amplification effect of ion distillation technology on the ion selectivity coefficient of amino acids. The method of this invention can achieve highly selective separation of various types of mixed amino acids, especially those with similar isoelectric points, structures, molecular weights, and / or charges. This invention provides an innovative method for the separation of mixed amino acids, and is expected to shorten the subsequent separation and purification process in amino acid production, reduce amino acid production costs, and improve the quality of amino acid products. Attached Figure Description

[0045] Figure 1 The membrane stack configuration of the anion distillation system used in the examples;

[0046] Figure 2 This is a schematic diagram of the anion distillation system and process used in the embodiments of the present invention;

[0047] Figure 3 This is a schematic diagram showing the change of glycine concentration over time in each distillation chamber in Example 1;

[0048] Figure 4 This is a schematic diagram showing the change of alanine concentration over time in each distillation chamber in Example 1;

[0049] Figure 5 This is a schematic diagram showing the change of glycine concentration over time in each distillation chamber in Example 2;

[0050] Figure 6 This is a schematic diagram showing the change of alanine concentration over time in each distillation chamber in Example 2; Detailed Implementation

[0051] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. The following content is merely illustrative and explanatory of the concept of the present invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the inventive concept or exceed the scope defined by the claims, all of which should fall within the protection scope of the present invention.

[0052] The ion distillation system used in Examples 1 and 2 below is a four-stage asymmetric anion distillation system. A schematic diagram of the experimental setup is shown below. Figure 1 As shown, the system includes three cation exchange membranes and four special monovalent / multivalent selective anion exchange membranes. Two ruthenium-iridium electrodes are installed on both sides of the ion distillation system as end plates and current collectors. One cation exchange membrane is placed near the anode and one near the cathode as a sealing septum. The four special monovalent / multivalent selective anion exchange membranes are repeatedly stacked on one end near the anode, and another cation exchange membrane is installed on one end near the cathode. Commercially available CMX and ACS membranes are used for the ion exchange. The membrane stack configuration is as follows: cathode plate - cathode chamber - cation exchange membrane - cation retention chamber - cation exchange membrane - feed chamber - anion exchange membrane - first-stage anion distillation chamber - anion exchange membrane - second-stage anion distillation chamber - anion exchange membrane - third-stage anion distillation chamber - anion exchange membrane - fourth-stage anion distillation chamber - cation exchange membrane - anode chamber - anode plate.

[0053] Example 1

[0054] This embodiment uses an anion distillation system to process a mixed solution of amino acids with similar isoelectric points, structures, molecular weights, and / or charges. The membrane stack configuration is as follows: Figure 1 As shown, the anion distillation system and process flow diagram are as follows: Figure 2 As shown. The simulated mixed amino acid solution was a mixture of glycine and alanine (both glycine and alanine concentrations were 0.1 mol / L). The pH of the mixed amino acid solution was adjusted to 8 using sodium hydroxide. Both glycine and alanine were negatively charged as a whole, but the optimal operating pH was not reached.

[0055] A mixed amino acid solution is introduced into the feed chamber. A sodium sulfate solution with a circulating concentration of 0.02 mol / L is used as an auxiliary electrolyte in the first to fourth stage anion distillation chambers; a sodium sulfate solution with a circulating concentration of 0.02 mol / L is used as an auxiliary electrolyte in the cation retention chamber; and a sodium sulfate solution with a circulating mass concentration of 3% is used as the electrode solution in the cathode and anode chambers.

[0056] The solutions in each membrane stack chamber were circulated in an ion distillation storage tank for 15 minutes until the liquid levels in each tank remained constant and the device was running stably. A constant current was then applied to the anion distillation unit, and the current and voltage changes during operation were monitored online using a power supply. A conductivity meter was used to detect changes in conductivity in each chamber during operation. During operation, samples were periodically taken from each anion distillation chamber, and an amino acid analyzer was used to analyze the changes in glycine and alanine concentrations in each distillation chamber. Figure 3 and Figure 4 As shown.

[0057] Example 2

[0058] This embodiment uses an anion distillation system to process a mixed solution of amino acids with similar isoelectric points, structures, molecular weights, and / or charges. The membrane stack configuration is as follows: Figure 1 As shown, the anion distillation system and process flow diagram are as follows: Figure 2 As shown. The simulated mixed amino acid solution was a mixture of glycine and alanine (both glycine and alanine concentrations were 0.1 mol / L). The pH of the mixed amino acid solution was adjusted to the optimal operating condition of 9.735 using sodium hydroxide. Both glycine and alanine were negatively charged as a whole.

[0059] A mixed amino acid solution is introduced into the feed chamber. A sodium sulfate solution with a concentration of 0.02 mol / L is circulated as an auxiliary electrolyte in the first to fourth stage anion distillation chambers; a sodium sulfate solution with a concentration of 0.02 mol / L is circulated as an auxiliary electrolyte in the cation retention chamber; and a sodium sulfate solution with a mass concentration of 3% is circulated in the cathode and anode chambers.

[0060] The solutions in each membrane stack chamber were circulated in an ion distillation storage tank for 15 minutes until the liquid levels in each tank remained constant and the device was running stably. A constant current was then applied to the anion distillation unit, and the current and voltage changes during operation were monitored online using a power supply. A conductivity meter was used to detect changes in conductivity in each chamber during operation. During operation, samples were periodically taken from each anion distillation chamber, and an amino acid analyzer was used to analyze the changes in glycine and alanine concentrations in each distillation chamber. Figure 5 and Figure 6 As shown.

[0061] The specific formula for calculating the selectivity coefficient (P) of glycine and alanine is as follows:

[0062]

[0063] Where A and B are types of amino acids, P A / B [A] represents the selectivity coefficient of amino acid A relative to amino acid B; [A] represents the concentration of amino acid A, and [B] represents the concentration of amino acid B; subscripts P and F represent the product chamber (i.e., the last stage distillation chamber) and the feed chamber, respectively; t represents time t, and 0 represents the initial time; [A] P,t [A] represents the concentration of amino acid A in the product chamber at time t; P,0 [B] Represents the concentration of amino acid A in the product chamber at time 0; P,t [B] represents the concentration of amino acid B in the product chamber at time t; P,0 [A] represents the concentration of amino acid B in the product chamber at time 0; F,t [B] represents the concentration of amino acid A in the feed chamber at time t; F,t This represents the concentration of amino acid B in the feed chamber at time t.

[0064] Based on the selectivity coefficient calculation formula described above, the selectivity coefficients of Examples 1 and 2 after 4 hours of experimentation can be calculated. The calculation process is as follows:

[0065] In Example 1, the concentration of glycine in the product chamber at the 4th hour [Gly] P,4 =0.000154077 mol / L, the concentration of alanine [Ala] in the product chamber at the 4th hour. P,4 = 0.00001200 mol / L. Initial concentration of glycine [Gly] in the product chamber. P,0 =0 mol / L, the initial concentration of alanine in the product chamber [Ala]. P,0 =0 mol / L. Since the feed chamber has a large volume (25 L), it is assumed that the molar ratio of glycine to alanine at the 4th hour is the same as the initial molar ratio, still 1. Substituting the above values, P is calculated. Gly / Ala =12.84.

[0066] In Example 2, the concentration of glycine in the product chamber at the 4th hour [Gly] P,4 =0.00028906 mol / L, the concentration of alanine [Ala] in the product chamber at the 4th hour. P,4 = 0.00001532 mol / L. Initial concentration of glycine [Gly] in the product chamber. P,0 =0 mol / L, the initial concentration of alanine in the product chamber [Ala].P,0 =0 mol / L. Since the feed chamber has a large volume (25 L), it is assumed that the molar ratio of glycine to alanine at the 4th hour is the same as the initial molar ratio, still 1. Substituting the above values, P is calculated. Gly / Ala =18.8681.

[0067] As can be seen from the above calculation process, when comparing the ion distillation system without pH adjustment to optimal operating conditions and the ion distillation system with pH adjustment to optimal operating conditions, the selectivity of the last stage for separating mixed solutions of amino acids with similar isoelectric points, structures, molecular weights and / or charges is improved, from the original 12.84 to 18.8681.

[0068] The results show that by adjusting the pH of the feed solution, changing the main charge form and ion ratio of amino acid ions in the solution, and combining the multi-stage sieving mechanism of ion distillation and the stage amplification effect of ion selectivity coefficient, fine sieving of mixed solutions of amino acids with similar isoelectric points, structures, molecular weights and / or charges can be successfully achieved.

[0069] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for separating mixed amino acids using an ion distillation system, characterized in that: The pH of the mixed amino acid solution was adjusted by controlling the isoelectric point of the two amino acids in the mixed amino acid solution, the overall charge type ions of the two amino acids in the mixed amino acid solution were determined, and then the selectivity coefficient of the two amino acids was gradually improved by using the corresponding ion distillation system. Based on the overall charge type of the two amino acids in the mixed amino acid mixture after pH adjustment, the ion distillation system is selected as follows: when the overall charge types of the two amino acids are positive and negative, respectively, an ion-coordinated distillation system is used; when one of the two amino acids is positively charged and the other is neutral or positively charged, a cation distillation system or an ion-coordinated distillation system is used; when one of the two amino acids is negatively charged and the other is neutral or negatively charged, an anion distillation system or an ion-coordinated distillation system is used. The specific methods are as follows: Let the isoelectric points of amino acid A and amino acid B in the mixed amino acid mixture be pI and pI, respectively. A With pI B ; If pI B -pI A >a, where a is any value between 0.6 and 1.2, the mixed amino acids are separated using the following method: First, adjust the pH of the mixed amino acid solution to pI. A <pH<pI B This results in amino acid A being negatively charged as a whole and amino acid B being positively charged as a whole in the mixed amino acid solution. An ion-coordinated distillation system is set up. A mixed amino acid solution to be treated is added to the feed chamber. A strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each cation distillation chamber and each anion distillation chamber. Under the drive of an electric field, positively charged amino acids A and B pass through the feed chamber sequentially through each stage of the cation exchange membrane. Based on the difference in migration rates between amino acids A and B, the selectivity coefficients of the two positively charged amino acids increase progressively in each stage of the cation distillation chamber. Simultaneously, under the drive of an electric field, negatively charged amino acids A and B pass through the feed chamber sequentially through each stage of the anion exchange membrane. Based on the difference in migration rates between amino acids A and B, the selectivity coefficients of the two negatively charged amino acids increase progressively in each stage of the anion distillation chamber. This allows for the separation of two amino acids in a mixed amino acid mixture; If 0 < pI B -pI A For amino acids ≤ a, where a is any value between 0.6 and 1.2, use either Method 1 or Method 2 to separate the mixed amino acids: Method 1: First, adjust the pH of the mixed amino acid solution to pH ≤ pI. A This results in amino acid A in the mixed amino acid solution being either electrically neutral or positively charged as a whole, while amino acid B is positively charged as a whole. A cation distillation system is set up, and the mixed amino acid solution to be treated is added to the feed chamber. A strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each cation distillation chamber and each anion retention chamber. Under the drive of an electric field, positively charged amino acid A and positively charged amino acid B pass through the cation exchange membranes of each stage from the feed chamber. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two positively charged amino acids increases step by step in each cation distillation chamber, thereby achieving the separation of the two amino acids in the mixed amino acid solution. Alternatively, an ion-coordinated distillation system can be set up. The mixed amino acid solution to be treated is added to the feed chamber, a strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each cation distillation chamber and each anion distillation chamber. Under the drive of an electric field, positively charged amino acid A and positively charged amino acid B pass through the cation exchange membranes of each stage from the feed chamber. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two positively charged amino acids increases step by step in each cation distillation chamber. At the same time, under the drive of an electric field, negatively charged amino acid A and negatively charged amino acid B pass through the anion exchange membranes of each stage from the feed chamber. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two negatively charged amino acids increases step by step in each anion distillation chamber. This allows for the separation of two amino acids in a mixed amino acid mixture; Method 2: First, adjust the pH of the mixed amino acid solution to pH ≥ pI. B This results in amino acid A in the mixed amino acid solution being negatively charged as a whole, while amino acid B is either electrically neutral or negatively charged as a whole. An anion distillation system is set up. The mixed amino acid solution to be treated is added to the feed chamber, a strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each anion distillation chamber and each cation retention chamber. Under the drive of an electric field, negatively charged amino acid A and negatively charged amino acid B pass through each anion exchange membrane step by step from the feed chamber. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two negatively charged amino acids increases step by step in each anion distillation chamber, thereby achieving the separation of the two amino acids in the mixed amino acid solution. Alternatively, an ion-coordinated distillation system can be set up. The mixed amino acid solution to be treated is added to the feed chamber, a strong electrolyte solution is added to the anode and cathode chambers, and an auxiliary electrolyte solution is added to each cation distillation chamber and each anion distillation chamber. Under the drive of an electric field, positively charged amino acid A and positively charged amino acid B pass through the cation exchange membranes of each stage from the feed chamber. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two positively charged amino acids increases step by step in each cation distillation chamber. At the same time, under the drive of an electric field, negatively charged amino acid A and negatively charged amino acid B pass through the anion exchange membranes of each stage from the feed chamber. Based on the difference in migration rate between amino acid A and amino acid B, the selectivity coefficient of the two negatively charged amino acids increases step by step in each anion distillation chamber. This allows for the separation of two amino acids in a mixed amino acid mixture.

2. The method for separating mixed amino acids using an ion distillation system according to claim 1, characterized in that: When 0 < pI B -pI A When ≤a, the pH of the mixed amino acid solution is adjusted according to the relationship between amino acid ion distribution and pH, so that amino acid A and amino acid B have the same charge type as a whole, while the ratio of the two amino acid ions with the same charge type is the largest difference.

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