Method for extracting amino acid from amino acid fermentation liquor by using ion rectification system

Abstract

The invention belongs to the field of separation and purification of organic compounds, and discloses a method for extracting amino acid from amino acid fermentation liquor by using an ion rectification system, the pH value of the amino acid fermentation liquor is precisely regulated, so that the charge states of amino acid ions and inorganic ions are different, and the amino acid is extracted from the amino acid fermentation liquor by using a special membrane arrangement mode of an ion rectification technology. Efficient separation of various components in the amino acid fermentation liquor is realized, and meanwhile, corresponding acid and alkali are recovered by combining the water molecule dissociation capability of the bipolar membrane. The invention provides an innovative method for extracting the amino acid from the amino acid fermentation liquor, the accurate separation of the amino acid in the fermentation liquor is realized, the recovery efficiency and the product purity are synchronously improved, the waste discharge is reduced, and the production cost of the amino acid is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of separation and purification of organic compounds, and specifically relates to a method for extracting amino acids from amino acid fermentation broth using an ion distillation system. Background Technology

[0002] Amino acids, as the basic building blocks of proteins, are ubiquitous in nature and organisms and play a vital role in human health. These amino acids are known for their biodegradability and have been widely used in food, pharmaceuticals, cosmetics, and biodegradable materials. Currently, amino acids are mainly produced through bio-fermentation or chemical synthesis. Bio-fermentation is the preferred method due to its environmental friendliness and renewability. However, the complex components in the fermentation broth (including organic acids, residual carbon sources, and inorganic electrolytes) require downstream purification processes involving multi-stage separation units, including acidification, crystallization, ion exchange, and membrane separation. These downstream refining processes typically account for 30-40% of the total production cost. Therefore, how to reduce the cost of amino acid separation through process optimization while achieving precise separation of the fermentation broth is a pressing issue for the current biorefining industry. Traditional amino acid fermentation broth treatment processes include precipitation, filtration, acidification, adsorption, and evaporation. This system has three significant drawbacks: (1) the process flow is lengthy and energy-intensive; (2) it requires the use of large quantities of sulfuric acid, ammonia, and other chemical supplements; and (3) it generates high chemical oxygen demand (COD) wastewater, creating significant treatment pressure. For example, the separation of glutamic acid from its sodium salt is typically achieved through isoelectric crystallization. However, the steric hindrance of biomacromolecules significantly reduces crystal yield. Furthermore, the fermentation broth still contains a large amount of glutamic acid after isoelectric crystallization. Compared to salts, amino acids have lower solubility in water, leading to low separation and recovery rates, requiring large amounts of acid and water to remove the corresponding salts. Recovering amino acids from fermentation broth using ion exchange requires large amounts of acid and alkali to regenerate the ion exchange resin, and the wastewater generated during the activation and washing processes causes serious environmental pollution. In addition, a single ion exchange unit cannot operate continuously; amino acid separation can only be achieved through intermittent feed-washing. While continuous separation can be achieved by connecting ion exchange units in series or parallel, the increased equipment investment and extended separation path still limit its economic viability.

[0003] Membrane separation, as a novel separation technology, utilizes selective membranes to regulate the transport of substances such as gases, vapors, and liquids at different mass transfer rates. The mass transfer rate of different substances is controlled by the permeability of the selective membrane to the feed components. These membranes can play an effective role in the separation and purification of amino acids through ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and electrodialysis (ED). Electrodialysis, as an electrochemical separation technology, uses a direct current to transfer charged substances from one solution to another through one or more selectively permeable membranes, thereby achieving enrichment or separation. Electrodialysis is widely used in the desalination of amino acids, for example, to adjust the pH to the isoelectric point of amino acids. Under the action of a direct current electric field, anions and cations migrate directionally towards the anode and cathode, respectively. Cations pass through cation exchange membranes, and anions pass through anion exchange membranes, while the amino acids remain electrically neutral in the feed solution, ultimately achieving desalination. However, conventional electrodialysis is typically used only for desalting neutral organic molecules. Amino acid fermentation broths often contain multiple solutes, including amino acids, inorganic ions, and neutral organic molecules, making precise separation of these components difficult with a single electrodialysis process. By combining multiple membrane separation technologies, inorganic ions and neutral organic molecules can be removed from amino acid fermentation broths separately, ultimately achieving selective separation of amino acids. Bipolar membrane electrodialysis (BMED) generates H₂ in situ through the dissociation of water molecules. + / OH - This technology has unique advantages in amino acid extraction and acid-base regeneration, and is widely used in organic acid production, organic wastewater treatment, and green chemical production. However, due to the limitations of electrodialysis's operating mechanism, conventional electrodialysis can only separate solutes with two different charge types, making it difficult to separate solutes with the same charge state. Therefore, the extraction of amino acids from amino acid fermentation broth requires the synergistic coupling of multiple technologies, resulting in long process routes, complex processes, and low integration. Ion-distillation is a novel electrically driven membrane separation technology that arranges multiple ion-exchange membranes of the same type on the same side. Currently, ion-distillation technology mainly addresses the separation of mixed metal ion systems, especially those generated during salt lake resource utilization. It utilizes the ion selectivity amplification effect of ion-distillation technology to separate solutes with properties close to those of ions (such as Li). + / Mg 2+ Separation between ions. Here, a distillation system is applied to an amino acid fermentation broth system, and by adjusting the pH to regulate the charge state of the amino acids, selective enrichment of different components in the fermentation broth is expected. Summary of the Invention

[0004] To achieve efficient separation of target products from amino acid fermentation broth and overcome the shortcomings of traditional extraction processes, this invention provides a method for extracting amino acids from amino acid fermentation broth using an ion distillation system. The core of this method lies in precisely controlling the pH value of the amino acid solution to regulate the dissociation state of the amino acids, giving them specific charged properties. Based on this, a multi-stage ion exchange membrane is used to achieve precise extraction of amino acids. This system differentiates the charging behavior of amino acids and inorganic ions, combined with the selective permeation characteristics of ion exchange membranes for different charged ions, ultimately achieving precise separation and purification of multiple solute components in the fermentation broth.

[0005] Amino acid fermentation broth is complex, containing amino acids, inorganic ions, and neutral organic molecules. Traditional methods for extracting amino acids from fermentation broth are complex, lengthy, and cause significant resource waste and environmental pollution. Electrodialysis, with its dual functions of selective separation and enrichment, is widely used in precision separation. Conventional electrodialysis uses alternating cation exchange membranes and anion exchange membranes, utilizing the membranes' selective permeability to enrich ions in different compartments. However, limited by the operating mechanism of electrodialysis and the separation principle of ion exchange membranes, electrodialysis technology struggles to achieve selective separation of ions with the same charge. This invention utilizes a special membrane arrangement in ion distillation, controlling the pH to regulate the charge state of amino acids, thus differentiating the charge states of amino acids and inorganic ions. This achieves precise separation of multiple solute components in the amino acid fermentation broth, while simultaneously recovering corresponding acids and bases by combining the water molecule dissociation capability of bipolar membranes. Ultimately, this achieves precise separation of amino acids, inorganic ions, and neutral organic molecules in the amino acid fermentation broth, as well as the simultaneous recovery of acids and bases.

[0006] The present invention solves the technical problem by adopting the following technical solution: The method of extracting amino acids from amino acid fermentation broth using ion distillation is characterized by: controlling the charge state of amino acids by adjusting pH, differentiating the charge states of amino acids and inorganic ions in the amino acid fermentation broth, using the special membrane arrangement of the ion distillation system to achieve precise separation of amino acids from other components, and simultaneously recovering the corresponding acids and bases by combining the ability of bipolar membranes to dissociate water molecules.

[0007] An amino acid with an isoelectric point less than 5 is considered an acidic amino acid; an amino acid with an isoelectric point greater than 9 is considered a basic amino acid; and an amino acid with an isoelectric point greater than or equal to 5 and less than or equal to 9 is considered a neutral amino acid. The method of this invention is applicable to the extraction of acidic, basic, and neutral amino acids. Specifically, the amino acids include, but are not limited to, 20 common amino acids involved in human life activities, such as glutamic acid (GA), glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), phenylalanine (Phe), serine (Ser), and proline (Pro).

[0008] Because amino acids contain both amino and carboxyl groups, they exhibit amphoteric characteristics, meaning they display different charge states under different pH conditions: when the solution pH is below the amino acid's isoelectric point (pI), the amino acid is positively charged; when the solution pH is above the amino acid's isoelectric point, the amino acid is negatively charged; and when the solution pH is equal to the amino acid's isoelectric point, the amino acid is electrically neutral. Different ion distillation systems are selected based on the type of amino acid: for acidic amino acids (which are negatively charged under neutral conditions, consistent with the charge type of inorganic anions), anion distillation systems are used; for basic amino acids (which are positively charged under neutral conditions, consistent with the charge type of inorganic cations), cation distillation systems are used; for neutral amino acids (which are electrically neutral under neutral conditions), the solution pH is first adjusted to make the amino acid positively or negatively charged. If it is positively charged, a cation distillation system is used; otherwise, an anion distillation system is used. Amino acids first pass through the first ion exchange membrane with inorganic ions carrying the same charge. Neutral organic molecules are retained in the feed chamber. Subsequently, the pH of the solution in the first-stage distillation chamber is adjusted to change the charge state of the amino acids. At this point, the inorganic ions that have passed through the first ion exchange membrane can continue to pass through the second ion exchange membrane, while the amino acids will be blocked by the second ion exchange membrane and enriched in the first-stage distillation chamber, ultimately achieving the purpose of precise separation of multiple components.

[0009] The solutes in the amino acid fermentation broth include amino acid A, inorganic cation B, inorganic anion C, and neutral organic molecule D. Let the isoelectric point of amino acid A be pI. Specifically, the method for extracting amino acids from the amino acid fermentation broth using an ion distillation system is as follows: 1. If the isoelectric point pI of amino acid A is <5 (i.e., amino acid A is an acidic amino acid, and amino acid A is negatively charged under neutral conditions), the following steps can be used to extract amino acids from the amino acid fermentation broth: Set up an anion distillation system (a two-stage anion distillation system can be used), and seal both ends of the anion distillation system with bipolar membranes; first, adjust the pH of the amino acid fermentation broth to neutral so that amino acid A is negatively charged as a whole; then add the amino acid fermentation broth to be treated into the feed chamber, and continuously control the pH of the solution in the feed chamber to neutral during electrodialysis; add a strong electrolyte solution (such as sodium sulfate solution) to the anode and cathode chambers, add an auxiliary alkali solution to each stage of the cation retention chamber, and add an auxiliary acid solution to each stage of the anion distillation chamber.

[0010] Under the influence of an applied electric field: Inorganic cation B permeates through the cation exchange membrane and is enriched in the cation retention chamber, where it combines with hydroxide ions to form a base; Amino acid A and inorganic anion C simultaneously permeate through the first anion exchange membrane; Using an auxiliary acid solution to adjust the pH of the solution in the first-stage anion distillation chamber to be ≤ the isoelectric point pI of amino acid A, amino acid A enters the first-stage anion distillation chamber and, after combining with hydrogen ions, becomes either electrically neutral or positively charged, and is thus blocked by the second anion exchange membrane and enriched in the first-stage anion distillation chamber, while the charge state of inorganic anion C remains unchanged and continues to permeate through the second anion exchange membrane and be enriched in the second-stage anion distillation chamber, where it combines with hydrogen ions to form an acid; Neutral organic molecule D, being uncharged, is retained in the feed chamber.

[0011] Based on the above steps, the precise separation of amino acid A, inorganic cation B, inorganic anion C, and neutral organic molecule D in the amino acid fermentation broth was achieved, as well as the effective recovery of amino acids, acids, and bases.

[0012] 2. If the isoelectric point pI of amino acid A is >9 (i.e., amino acid A is a basic amino acid, and amino acid A is positively charged under neutral conditions), the following steps can be used to extract amino acids from the amino acid fermentation broth: A cation distillation system (a two-stage cation distillation system can be used) is set up, and both ends of the cation distillation system are sealed with bipolar membranes. First, the pH of the amino acid fermentation broth is adjusted to neutral so that amino acid A is positively charged as a whole. Then, the amino acid fermentation broth to be treated is added to the feed chamber, and the pH of the solution in the feed chamber is continuously controlled to be neutral during electrodialysis. A strong electrolyte solution (such as sodium sulfate solution) is added to the anode and cathode chambers, an auxiliary alkali solution is added to each stage of the cation distillation chamber, and an auxiliary acid solution is added to each stage of the anion retention chamber.

[0013] Under the influence of an applied electric field: Inorganic anions C pass through the anion exchange membrane and are enriched in the anion retention chamber, where they combine with hydrogen ions to form acids; Amino acid A and inorganic cation B simultaneously pass through the first cation exchange membrane. Using an auxiliary alkaline solution to adjust the pH of the solution in the first-stage cation distillation chamber to be greater than or equal to the isoelectric point pI of amino acid A, amino acid A enters the first-stage cation distillation chamber, loses hydrogen ions, and becomes either electrically neutral or negatively charged. It is then blocked by the second cation exchange membrane and enriched in the first-stage cation distillation chamber. Meanwhile, the charge state of inorganic cation B remains unchanged, continuing to pass through the second cation exchange membrane and be enriched in the second-stage cation distillation chamber, where it combines with hydroxide ions to form bases; Neutral organic molecules D are uncharged and are retained in the feed chamber.

[0014] Based on the above steps, the precise separation of amino acid A, inorganic cation B, inorganic anion C, and neutral organic molecule D in the amino acid fermentation broth was achieved, as well as the effective recovery of amino acids, acids, and bases.

[0015] 3. If the isoelectric point of amino acid A is greater than or equal to 5 and less than or equal to 9 (i.e., amino acid A is a neutral amino acid, and amino acid A is electrically neutral as a whole under neutral conditions), extract amino acids from the amino acid fermentation broth using either Method 1 or Method 2 as follows: Method 1: A cation distillation system (a two-stage cation distillation system can be used) is set up, and both ends of the cation distillation system are sealed with bipolar membranes. First, the pH of the amino acid fermentation broth is adjusted to <5 so that amino acid A in the amino acid fermentation broth is positively charged. Then, the amino acid fermentation broth to be treated is added to the feed chamber, and the pH of the solution in the feed chamber is continuously controlled to <5 during the electrodialysis process. A strong electrolyte solution (such as sodium sulfate solution) is added to the anode and cathode chambers, an auxiliary alkaline solution is added to each stage of the cation distillation chamber, and an auxiliary acid solution is added to each stage of the anion retention chamber.

[0016] Under the influence of an applied electric field: Inorganic anions C pass through the anion exchange membrane and are enriched in the anion retention chamber, where they combine with hydrogen ions to form acids; Amino acid A and inorganic cation B simultaneously pass through the first cation exchange membrane; Using an auxiliary alkaline solution to adjust the pH of the solution in the first-stage cation distillation chamber to be greater than or equal to the isoelectric point pI of amino acid A, amino acid A enters the first-stage cation distillation chamber, loses hydrogen ions, and becomes either electrically neutral or negatively charged, thus being blocked by the second cation exchange membrane and enriched in the first-stage cation distillation chamber, while the charge state of inorganic cation B remains unchanged and continues to pass through the second cation exchange membrane to be enriched in the second-stage cation distillation chamber, where it combines with hydroxide ions to form alkalis; Neutral organic molecules D are uncharged and are retained in the feed chamber.

[0017] Based on the above steps, the precise separation of amino acid A, inorganic cation B, inorganic anion C, and neutral organic molecule D in the amino acid fermentation broth was achieved, as well as the effective recovery of amino acids, acids, and bases.

[0018] Method 2: Set up an anion distillation system (a two-stage anion distillation system can be used), and seal both ends of the anion distillation system with bipolar membranes; first, adjust the pH of the amino acid fermentation broth to >9 so that amino acid A in the amino acid fermentation broth is negatively charged as a whole; then add the amino acid fermentation broth to be treated into the feed chamber, and continuously control the pH of the solution in the feed chamber to >9 during the electrodialysis process; add a strong electrolyte solution (such as sodium sulfate solution) to the anode and cathode chambers, add an auxiliary alkali solution to each stage of the cation retention chamber, and add an auxiliary acid solution to each stage of the anion distillation chamber.

[0019] Under the influence of an applied electric field: Inorganic cation B permeates through the cation exchange membrane and is enriched in the cation retention chamber, where it combines with hydroxide ions to form a base; Amino acid A and inorganic anion C simultaneously permeate through the first anion exchange membrane; Using an auxiliary acid solution to adjust the pH of the solution in the first-stage anion distillation chamber to be ≤ the isoelectric point pI of amino acid A, amino acid A enters the first-stage anion distillation chamber and, after combining with hydrogen ions, becomes either electrically neutral or positively charged, and is thus blocked by the second anion exchange membrane and enriched in the first-stage anion distillation chamber, while the charge state of inorganic anion C remains unchanged and continues to permeate through the second anion exchange membrane and be enriched in the second-stage anion distillation chamber, where it combines with hydrogen ions to form an acid; Neutral organic molecule D, being uncharged, is retained in the feed chamber.

[0020] Based on the above steps, the precise separation of amino acid A, inorganic cation B, inorganic anion C, and neutral organic molecule D in the amino acid fermentation broth was achieved, as well as the effective recovery of amino acids, acids, and bases.

[0021] Furthermore, when 5≤pI≤9, according to the relationship between amino acid ion distribution and pH, the proportion of positively or negatively charged amino acid ions of amino acid A in the fermentation broth is maximized. At this time, the pH of the feed solution is the optimal operating pH. Note that the pH of the feed solution chamber needs to be kept stable during the experiment. In the first stage cation distillation chamber of a two-stage cation distillation system or the first stage anion distillation chamber of a two-stage anion distillation system, the total amount of inorganic ions in the auxiliary solution is the same as the total amount of amino acid A in the feed solution chamber. At this time, the theoretical purity of extracted amino acid A is the highest.

[0022] Furthermore, the acid or base used to adjust the pH of the mixed amino acid solution is an inorganic acid or inorganic base.

[0023] Furthermore, the ion distillation system used has an asymmetric structure and has two distillation stages.

[0024] 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.

[0025] Furthermore, the end-capping diaphragm used in the ion distillation system is a bipolar membrane, used to recover the corresponding acids and bases.

[0026] The ion distillation system of the present invention includes a cation distillation system and an anion distillation system. The structure of the cation distillation system is described in patent CN 113663519 A, and the structure of the anion distillation system is described in patent CN 113663517 A. Alternatively, an ion-coordinated distillation system integrating cation and anion distillation functions can be used (the structure of which is described in patent CN113663518 A).

[0027] The beneficial effects of this invention are as follows: By precisely controlling the pH of the amino acid fermentation broth, this invention creates a difference in the charge states of amino acids and inorganic ions. Utilizing the unique membrane arrangement of ion distillation technology, it achieves effective separation of multiple components in the amino acid fermentation broth. The method of this invention can achieve precise separation of amino acids, inorganic anions and cations, and neutral organic molecules in various amino acid fermentation broths, while simultaneously recovering the corresponding acids and bases. This invention provides an innovative method for extracting amino acids from amino acid fermentation broth, and is expected to optimize the separation process route in amino acid production, thereby reducing the production cost of amino acids. Attached Figure Description

[0028] Figure 1 This is a schematic diagram showing the changes in the ionization state and ionic composition of glutamate ions with the pH of the fermentation broth. Figure 2 The membrane stack configuration of the anion distillation system used in the examples; Figure 3 The following is a schematic diagram showing the changes in ion concentration in different compartments under operating conditions of 0.22 A in the examples: (a) acid compartment, (b) product compartment, (c) feed compartment, (d) alkali compartment; Figure 4 The following is a schematic diagram showing the changes in ion concentration in different compartments under operating conditions of 0.44 A in the examples: (a) acid compartment, (b) product compartment, (c) feed compartment, (d) alkali compartment; Figure 5 The following is a schematic diagram showing the changes in ion concentration in different compartments under operating conditions of 0.66 A in the examples: (a) acid compartment, (b) product compartment, (c) feed compartment, (d) alkali compartment; Figure 6 The following is a schematic diagram of the changes in ion concentration in different compartments after condition optimization in the examples: (a) acid compartment, (b) product compartment, (c) feed compartment, (d) alkali compartment; Figure 7 The X-ray diffraction (XRD) analysis (a) and X-ray photoelectron spectroscopy (XPS) analysis (b) of the glutamic acid product in the examples are shown. Figure 8 The following are scanning electron microscopy (SEM) analyses (a corresponds to before the experiment, b corresponds to after the experiment) and infrared spectroscopy (ATR-FTIR) analyses (c corresponds to before the experiment, d corresponds to after the experiment) of the anion exchange membrane surface between the feed chamber and the product chamber before and after the experiment in the example. Detailed Implementation

[0029] 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.

[0030] The following examples use glutamic acid fermentation broth (the main components of which include glutamic acid GA, glucose Glu, and SO4). 2- NH 4+ Taking glutamic acid as an example, the effectiveness of the method of the present invention is verified. The structure of glutamic acid is shown below:

[0031] Glutamic acid (GA) is a typical acidic amino acid, containing two carboxyl groups and one amino group in its molecule. It is an organic compound with an isoelectric point of 3.22. In aqueous solution, glutamic acid (GA) undergoes the following dissociation: pK1=2.19; pK2=4.25; pK3=9.67; Where pK1 and pK2 represent the two-step dissociation constants of the carboxyl group of glutamic acid, and pK3 represents the dissociation constant of the amino group of glutamic acid. Its isoelectric point is 3.22, meaning that when the solution pH = 3.22, the glutamic acid in the solution is electroneutrally neutral. According to the relationship between glutamic acid ion distribution and pH (e.g....), Figure 1 As shown in the figure, when the solution pH < 2, glutamic acid is in a positively charged form; when the solution pH = 3.22, glutamic acid is electrically neutral; when the solution pH = 7, glutamic acid is in a negatively charged form; and when the solution pH > 12, glutamic acid is in a negatively charged form.

[0032] Example 1 This embodiment uses an anion distillation system to extract glutamic acid from the glutamic acid fermentation broth. The membrane stack configuration is as follows: Figure 2As shown, the system includes one cation exchange membrane (CEM), two anion exchange membranes (AEM), and two bipolar membranes (BP). Two ruthenium-iridium electrodes are installed on both sides of the ion distillation system as end plates and current collectors. One bipolar membrane is placed near the anode and one near the cathode as a sealing septum. Two anion exchange membranes are stacked repeatedly near the anode side, and another cation exchange membrane is installed near the cathode side. The commercially available ion exchange membranes used are CMX cation exchange membrane, AMV anion exchange membrane, and BP-1 bipolar membrane. The membrane stack configuration is: anode plate - anode chamber - bipolar membrane - acid chamber (second-stage anion distillation chamber) - anion exchange membrane - product chamber (first-stage anion distillation chamber) - anion exchange membrane - feed chamber - cation exchange membrane - alkali chamber (cation retention chamber) - bipolar membrane - cathode chamber - cathode plate. The effective area of ​​each membrane and electrode is 22 cm². 2 .

[0033] The simulated glutamic acid fermentation broth contains glucose, glutamic acid, sulfate, and ammonium. The pH of the simulated fermentation broth is adjusted to 7 using ammonia water. At this point, the glutamic acid in the fermentation broth is in a negatively charged form.

[0034] The feed chamber was circulated with 200 mL of simulated glutamic acid fermentation broth ((NH4)2SO4, GA-NH4, and Glu concentrations were all 0.05 mol / L), and the pH of the solution in the feed chamber was continuously adjusted to neutral by adding ammonia during electrodialysis. The first-stage anion distillation chamber was circulated with 100 mL of 0.05 mol / L sulfuric acid solution as an auxiliary acid solution, and the second-stage anion distillation chamber was circulated with 200 mL of 0.05 mol / L sulfuric acid solution as an auxiliary acid solution. The cation retention chamber was circulated with 200 mL of 0.1 mol / L ammonia solution as an auxiliary alkali solution, and the cathode and anode chambers were circulated with 200 mL of 3% sodium sulfate solution as electrode solutions.

[0035] The solutions in each chamber of the membrane stack were circulated in the ion distillation storage tank for 15 minutes until the liquid levels in each chamber 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 the conductivity changes in each chamber during operation. During operation, samples were taken periodically from the feed chamber and each anion distillation chamber, and the changes in glucose and glutamate concentrations in the feed chamber and each distillation chamber were analyzed using a bioanalyzer. Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to detect and analyze the changes in sulfate concentrations in the feed chamber and each distillation chamber.

[0036] In this embodiment, the solution was circulated between the compartments using a peristaltic pump at a flow rate of 200 mL / min. The experiment was conducted under constant current conditions (0.22 A, 0.44 A, 0.66 A) maintained by a DC power supply system. Operation was stopped when the conductivity of the solution in the feed chamber fell below 200 μS / cm.

[0037] Experimental results under a series of current conditions are as follows Figure 3-5 As shown in the figure, it can be seen from the entire experimental process that SO4 2- GA - NH4 + Glu and other ions showed a gradual separation and enrichment trend in different compartments. In the feed chamber, except for glucose which was retained due to its neutral charge, other charged ions were gradually removed. At 0.22 A, SO42- in the feed chamber... 2- and GA - The concentrations of SO42- decreased from 4.88 g / L and 6.3 g / L to 0 g / L and 0.4 g / L, respectively, achieving desalination efficiencies of 100% and 93.65%. SO42- in the acid chamber... 2- The concentration increased from 4.84 g / L to 11.12 g / L. In the product room, the initial GA... - The concentration remained stable until SO4 in the feed solution was stable. 2- The concentration decreased to 0.92 g / L, and the GA concentration in the product chamber... - The concentration rose sharply to 12.6 g / L. Similarly, the SO4 concentration in the product chamber... 2- The concentration initially remained stable, but subsequently decreased due to its interaction with GA. - The competitive migration gradually decreases. At 0.44 A and 0.66 A, the ion flux increases with increasing current density, but the operating time decreases significantly. At 0.22 A, 0.44 A, and 0.66 A, based on SO42-... 2- and GA - The calculated current efficiencies were 34.12%, 56.85%, and 61.70%, respectively. This is because the prolonged ion migration time at low currents enhances proton leakage from the acid chamber to the product chamber via diffusion, while the shorter operating time at high currents reduces the overall H₂O₂ concentration. + Leakage. Therefore, the process should continue to operate while maintaining high current control.

[0038] To further improve the purity of the amino acid product obtained in the product chamber, the glutamic acid separation experiment was optimized to a certain extent. In the optimized system, the buffering effect of the auxiliary electrolyte concentration (H₂SO₄) in the product chamber was minimized, and the concentration of the sulfuric acid solution in the first-stage anion distillation chamber was changed from 0.05 mol / L to 0.025 mol / L to ensure mass conservation. Figure 6The results show that after 200 min of treatment under a constant current of 0.44 A, no sulfate ions were detected in the feed chamber, and the glutamic acid concentration [GA] = 0.8 g / L; the sulfate concentration in the acid chamber changed from 4.76 g / L to 11.50 g / L, and no glucose or glutamic acid was detected in the acid chamber; the sulfate ion concentration in the product chamber [SO4]... 2- The concentration of glucose in the product was 0.030 g / L, the concentration of glutamate [GA] was 12.75 g / L, and no glucose was detected in the product chamber. The purity of glutamate in the product chamber was higher than 99%. The aqueous solution of the product was vacuum dried to obtain a homogeneous GA product, which was then analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Figure 7 As shown, the XRD curve of the product sample is similar to that of AR-grade GA. XPS analysis showed clear C1s, N1s, and O1s peaks, confirming the high purity of the solid product, which was identified as glutamic acid. Finally, scanning electron microscopy (SEM) analysis (a corresponds to before the experiment, b corresponds to after the experiment) and ATR-FTIR analysis (c corresponds to before the experiment, d corresponds to after the experiment) were performed on the surface of the anion exchange membrane between the feed chamber and the product chamber before and after the experiment. The results showed that there was no significant change in the morphology of the membrane surface before and after the experiment, and the characteristic peaks also remained unchanged, indicating that there was no organic contamination on the membrane surface, which proved the stability of the system.

[0039] The results above show that by adjusting the pH of the feed liquid and the first-stage ion distillation chamber, differentiating the charge states of amino acid ions and inorganic anions in the solution, and combining the special membrane arrangement of the same type and side in ion distillation, the present invention has successfully achieved the precise separation of amino acids, inorganic cations and anions, and neutral organic molecules in amino acid fermentation broth, while simultaneously recovering the corresponding acids and bases.

[0040] 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 extracting amino acids from amino acid fermentation broth using an ion distillation system, characterized in that: By adjusting the pH to control the charge state of amino acids, the charge states of amino acids and inorganic ions in the amino acid fermentation broth are differentiated. An ion distillation system is used to achieve precise separation of amino acids from other components. At the same time, the ability of bipolar membranes to dissociate water molecules is combined to recover the corresponding acids and bases.

2. The method for extracting amino acids from amino acid fermentation broth using an ion distillation system according to claim 1, characterized in that: When the amino acid is an acidic amino acid with an isoelectric point of less than 5, an anion distillation system is used to adjust the pH of the amino acid fermentation broth to neutral, so that the acidic amino acid as a whole is negatively charged, consistent with the charge type of inorganic anions. When the amino acid is a basic amino acid with an isoelectric point greater than 9, a cationic distillation system is used to adjust the pH of the amino acid fermentation broth to neutral, so that the basic amino acid as a whole is positively charged, consistent with the charge type of inorganic cations; when the amino acid is a neutral amino acid with an isoelectric point greater than or equal to 5 and less than or equal to 9, the pH of the amino acid fermentation broth is adjusted to make the amino acid as a whole positively or negatively charged. A cationic distillation system is used for overall positive charging, and an anionic distillation system is used for overall negative charging.

3. The method for extracting amino acids from amino acid fermentation broth using an ion distillation system according to claim 2, characterized in that: Amino acids first pass through the first ion exchange membrane with inorganic ions carrying the same charge, while neutral organic molecules are retained in the feed chamber. Subsequently, the pH of the solution in the first-stage distillation chamber is adjusted to change the charge state of the amino acids. At this time, the corresponding inorganic ions continue to pass through the second ion exchange membrane, while the amino acids are blocked by the second ion exchange membrane, thus achieving the separation of the components in the amino acid fermentation broth.

4. The method for extracting amino acids from amino acid fermentation broth using an ion distillation system according to claim 2, characterized in that, If the isoelectric point of the amino acid is less than 5, the specific steps for extracting the amino acid from the amino acid fermentation broth using an ion distillation system are as follows: An anion distillation system was set up, and both ends of the anion distillation system were sealed with bipolar membranes; first, the pH of the amino acid fermentation broth was adjusted to neutral conditions so that the amino acids were negatively charged as a whole; The amino acid fermentation broth to be treated was added to the feed chamber, and the pH of the solution in the feed chamber was continuously adjusted to be neutral during the electrodialysis process; strong electrolyte solutions were added to the anode and cathode chambers, auxiliary alkaline solutions were added to each stage of the cation retention chambers, and auxiliary acid solutions were added to each stage of the anion distillation chambers. Under the influence of an external electric field: Inorganic cations pass through the cation exchange membrane and are enriched in the cation retention chamber, where they combine with hydroxide ions to form a base; Negatively charged amino acids and inorganic anions pass through the first anion exchange membrane simultaneously; The pH of the solution in the first-stage anion distillation chamber is adjusted to be less than or equal to the isoelectric point of the amino acids using an auxiliary acid solution; After entering the first-stage anion distillation chamber and combining with hydrogen ions, the amino acids become either electrically neutral or positively charged as a whole, and are thus blocked by the second anion exchange membrane and enriched in the first-stage anion distillation chamber. Inorganic anions, whose charged state remains unchanged, continue to pass through the second anion exchange membrane and are enriched in the second-stage anion distillation chamber, where they combine with hydrogen ions to form acids; neutral organic molecules remain in the feed chamber. Based on the above steps, the precise separation of amino acids, inorganic cations, inorganic anions, and neutral organic molecules in the amino acid fermentation broth, as well as the effective recovery of amino acids, acids, and bases, were achieved.

5. The method for extracting amino acids from amino acid fermentation broth using an ion distillation system according to claim 2, characterized in that, If the isoelectric point of the amino acid is greater than 9, the specific steps for extracting the amino acid from the amino acid fermentation broth using an ion distillation system are as follows: A cation distillation system was set up, and both ends of the cation distillation system were sealed with bipolar membranes. First, the pH of the amino acid fermentation broth was adjusted to neutral conditions so that the amino acids were positively charged. The amino acid fermentation broth to be treated was added to the feed chamber, and the pH of the solution in the feed chamber was continuously adjusted to neutral during the electrodialysis process. Strong electrolyte solutions were added to the anode and cathode chambers, auxiliary alkaline solutions were added to each stage of the cation distillation chamber, and auxiliary acid solutions were added to each stage of the anion retention chamber. Under the influence of an applied electric field: Inorganic anions pass through the anion exchange membrane and are enriched in the anion retention chamber, where they combine with hydrogen ions to form acids; Positively charged amino acids and inorganic cations pass through the first cation exchange membrane simultaneously; The pH of the solution in the first-stage cation distillation chamber is adjusted to be greater than or equal to the isoelectric point of the amino acids using an auxiliary alkaline solution. After the amino acids enter the first-stage cation distillation chamber and lose hydrogen ions, they become either electrically neutral or negatively charged as a whole, and are thus blocked by the second cation exchange membrane and enriched in the first-stage cation distillation chamber. Inorganic cations, whose charged state remains unchanged, continue to pass through the second cation exchange membrane and accumulate in the second-stage cation distillation chamber, where they combine with hydroxide ions to form a base; neutral organic molecules remain in the feed chamber. Based on the above steps, the precise separation of amino acids, inorganic cations, inorganic anions, and neutral organic molecules in the amino acid fermentation broth, as well as the effective recovery of amino acids, acids, and bases, were achieved.

6. The method for extracting amino acids from amino acid fermentation broth using an ion distillation system according to claim 2, characterized in that, If the isoelectric point of the amino acid is greater than or equal to 5 and less than or equal to 9, the step of extracting the amino acid from the amino acid fermentation broth using an ion distillation system is either Method 1 or Method 2: Method 1: A cation distillation system was set up, and both ends of the cation distillation system were sealed with bipolar membranes; first, the pH of the amino acid fermentation broth was adjusted to <5 so that the amino acids in the amino acid fermentation broth were positively charged as a whole; The amino acid fermentation broth to be treated was added to the feed chamber, and the pH of the solution in the feed chamber was continuously controlled to be <5 during the electrodialysis process; strong electrolyte solutions were added to the anode and cathode chambers, auxiliary alkaline solutions were added to each stage of cation distillation chambers, and auxiliary acid solutions were added to each stage of anion retention chambers. Under the influence of an applied electric field: Inorganic anions pass through the anion exchange membrane and are enriched in the anion retention chamber, where they combine with hydrogen ions to form acids; Positively charged amino acids and inorganic cations pass through the first cation exchange membrane simultaneously; The pH of the solution in the first-stage cation distillation chamber is adjusted to be greater than or equal to the isoelectric point of the amino acids using an auxiliary alkaline solution. After the amino acids enter the first-stage cation distillation chamber and lose hydrogen ions, they become either electrically neutral or negatively charged as a whole, and are thus blocked by the second cation exchange membrane and enriched in the first-stage cation distillation chamber. Inorganic cations, whose charged state remains unchanged, continue to pass through the second cation exchange membrane and accumulate in the second-stage cation distillation chamber, where they combine with hydroxide ions to form a base; neutral organic molecules remain in the feed chamber. Based on the above steps, the precise separation of amino acids, inorganic cations, inorganic anions, and neutral organic molecules in the amino acid fermentation broth, as well as the effective recovery of amino acids, acids, and bases, were achieved. Method 2: An anion distillation system was set up, and both ends of the anion distillation system were sealed with bipolar membranes. First, the pH of the amino acid fermentation broth was adjusted to be greater than 9 so that the amino acids in the amino acid fermentation broth were negatively charged. The amino acid fermentation broth to be treated was added to the feed chamber, and the pH of the solution in the feed chamber was continuously adjusted to be greater than 9 during the electrodialysis process. Strong electrolyte solutions were added to the anode and cathode chambers, auxiliary alkaline solutions were added to each stage of the cation retention chamber, and auxiliary acid solutions were added to each stage of the anion distillation chamber. Under the influence of an external electric field: Inorganic cations pass through the cation exchange membrane and are enriched in the cation retention chamber, where they combine with hydroxide ions to form a base; Negatively charged amino acids and inorganic anions pass through the first anion exchange membrane simultaneously; The pH of the solution in the first-stage anion distillation chamber is adjusted to be less than or equal to the isoelectric point of the amino acids using an auxiliary acid solution; After entering the first-stage anion distillation chamber and combining with hydrogen ions, the amino acids become either electrically neutral or positively charged as a whole, and are thus blocked by the second anion exchange membrane and enriched in the first-stage anion distillation chamber. Inorganic anions, whose charged state remains unchanged, continue to pass through the second anion exchange membrane and are enriched in the second-stage anion distillation chamber, where they combine with hydrogen ions to form acids; neutral organic molecules remain in the feed chamber. Based on the above steps, the precise separation of amino acids, inorganic cations, inorganic anions, and neutral organic molecules in the amino acid fermentation broth, as well as the effective recovery of amino acids, acids, and bases, were achieved.

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