A method for extracting L-lysine from a fermentation broth

Abstract

The application discloses a method for extracting L-lysine from fermentation liquor and belongs to the technical field of L-lysine extraction. The method comprises the following steps: ceramic membrane filtration, inorganic salt removal, ion exchange, activated carbon decolorization and crystallization. In the ion exchange, distilled water and corn starch are mixed, gelatinized at 93-97 DEG C, naturally cooled to room temperature, polyethylene glycol 400 is added, stirred at room temperature, mixed with the fermentation liquor after inorganic salt removal, stirred at room temperature, adjusted to a pH value of 1.9-2.1, introduced into an ion exchange column for adsorption, introduced into the ion exchange column with ammonia water as an eluent for desorption, collected the effluent, and obtained an eluent containing L-lysine. The method can improve the yield and purity of the extracted L-lysine at the same time, and the yield of the extracted L-lysine is less affected by the residual sugar content in the fermentation liquor.

Description

Technical Field

[0001] This invention relates to the field of L-lysine extraction technology, and more specifically to a method for extracting L-lysine from fermentation broth. Background Technology

[0002] L-Lysine, chemically known as 2,6-diaminohexanoic acid, is one of the eight essential amino acids that humans and animals cannot synthesize themselves, and is also known as the first limiting amino acid. L-Lysine is a white hexagonal crystal, readily soluble in water, and widely used in food, feed, and pharmaceutical industries. In the food industry, L-Lysine is used as a food fortifier, promoting height and weight gain in children, promoting skeletal muscle growth in animals, and reducing unpleasant odors in food. Furthermore, L-Lysine can be used as a coloring and color-developing agent, preventing discoloration and fading of meat during storage. In the feed industry, given the low L-Lysine content in animal feed and the loss during processing, which can lead to nutritional imbalances, it is necessary to add L-Lysine to animal feed. Studies have found that adding appropriate amounts of L-Lysine to feed can effectively promote animal growth and development, increase protein synthesis in animals, save feed, and reduce costs. In the medical field, L-lysine can be used as a thrombosis preventive agent, an adjunct to diuretics, and has a significant effect on the adjunctive treatment of anemia. It can also improve drug solubility and reduce drug side effects.

[0003] The main methods for producing L-lysine include extraction, chemical synthesis, and microbial fermentation. Among these three methods, microbial fermentation is currently the most important industrial method for producing L-lysine. The main strains used in microbial fermentation are *Escherichia coli* and *Corynebacterium glutamicum*. Because *Escherichia coli* itself has a certain degree of toxicity, *Corynebacterium glutamicum* is currently the primary starting strain used for selecting L-lysine production strains.

[0004] When producing L-lysine via microbial fermentation using *Corynebacterium glutamicum* as the starting strain, glucose is the primary carbon source, and nitrogen sources are divided into inorganic and organic sources. The main inorganic nitrogen source is (NH4)2SO4, while organic nitrogen sources include corn steep liquor and soybean protein hydrolysate. Corn steep liquor, a byproduct of corn starch production, contains abundant polypeptides, auxins, free amino acids, and soluble proteins, making it a good nitrogen source for microbial amino acid fermentation. However, due to the presence of large amounts of pigments and other proteins in corn steep liquor, the fermentation broth after fermentation contains microbial cells, proteins, and inorganic salt ions (such as Mg2+). 2+ Ca 2+ K + NH4 + PO4 3- SO42- Cl - Impurities such as pigments, residual sugars, amino acids, and organic acids make it more difficult to extract L-lysine from the fermentation broth.

[0005] Currently, the main methods for extracting L-lysine from fermentation broth are as follows: Chinese patent CN104230732B discloses a method for extracting L-lysine from molasses fermentation broth, including solid-liquid separation, membrane filtration, solid recovery, chemical extraction, and back-extraction steps. Specifically, after removing solid substances such as bacteria and colloids from the molasses fermentation broth, it is thoroughly mixed with the extract, shaken at room temperature, and after the extraction reaches equilibrium, the extract and raffinate are separated. The extract is back-extracted with hydrochloric acid to recover the organic solvent, and the raffinate is directly recovered as a component of the fermentation medium. The extractant used in the chemical extraction is cyclohexane as a diluent, which is obtained by diluting 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester. The back-extraction agent used in the back-extraction is a hydrochloric acid solution. However, Li Qian disclosed in "Research on the Crystallization Process of L-Lysine Hydrochloride" (Master's Thesis, Hebei University of Science and Technology, 2010) that the introduction of the extractant will increase operating costs and input costs, lengthen the production process, and will inevitably have a certain impact on product quality.

[0006] Chinese patent CN103992964B discloses a method for producing lysine using a high-pH-tolerant bacterial strain and fermentation. Specifically, the fermentation broth is filtered through a membrane to remove impurities such as bacterial cells and large protein molecules. After filtration, the fermentation broth is not subjected to adsorption / desorption via ion exchange resin; instead, other ions and impurities are removed directly through decolorization filtration and other methods. Lysine hydrochloride is then directly produced through processes such as concentration, acid adjustment, crystallization, recrystallization (mother liquor), centrifugation, and drying. This patent simplifies the extraction method by eliminating the need for adsorption / desorption of the fermentation broth using ion exchange resin. However, this extraction method is only applicable to fermentation broths with low sulfate ion concentrations, limiting its applicability.

[0007] Chinese patent CN1041824C discloses a method for extracting L-lysine from fermentation broth. Specifically, the method involves first removing mycelium and protein from the fermentation broth using an organic or inorganic flocculant, and then removing calcium from the fermentation broth using oxalic acid and sodium tripolyphosphate. 2+ and Mg 2+ The process involves adsorption and desorption of L-lysine using ion exchange resin, followed by decolorization of the desorbed solution using an adsorbent. Finally, the decolorized solution is concentrated, and L-lysine is crystallized from the concentrate. While this patented method effectively removes impurities from the fermentation broth, it has the following drawbacks: In this patent, oxalic acid and sodium tripolyphosphate are used to remove Ca from the fermentation broth. 2+ and Mg 2+Then, the pH of the solution was adjusted to 6, polyacrylamide flocculant was added, and if necessary, a small amount of bentonite and a small amount of diatomaceous earth were added to aid filtration. After filtration, the pretreated L-lysine fermentation broth was obtained. The pH was then adjusted to 2 and passed through an ion exchange resin for adsorption and desorption. However, Song Mingyue disclosed in "Study on the Binding Ability of Chelating Agents to Calcium Ions and the Chelating Process of Polyphosphate" (Master's Thesis, Tianjin University, 2021) that sodium tripolyphosphate can chelate calcium ions. The pH value has a significant impact on the chelation process. The higher the pH value, the higher the content of soluble chelate products. However, after adjusting the pH value to 2, the content of soluble chelate products decreased, which in turn affected the adsorption process and led to a decrease in the yield of extracted L-lysine.

[0008] In this patent, after adjusting the pH to 2, adsorption and desorption are carried out by passing the solution through an ion exchange resin. Xiang Lingzhi et al., in their study "Performance Study of L-Tryptophan Adsorption by 732 Type Cation Exchange Resin" (Guangdong Chemical Industry, 2005), disclosed that glucose is a polyhydroxy aldehyde. The hydrogen bonding between glucose and water makes the arrangement of water molecules more ordered, hindering the rotation of water molecules and preventing them from orienting themselves according to an external electric field. Therefore, as the glucose content increases, the dielectric constant of the solution decreases, and the adsorption rate of amino acids by the ion exchange resin decreases. Similarly, for L-lysine, as the glucose concentration in the fermentation broth increases, the yield of extracted L-lysine also decreases.

[0009] In this patent, after adjusting the pH value to 2, ion exchange resin is passed through for adsorption and desorption, and then activated carbon is used to decolorize the desorbed solution. However, Chen Hengqing disclosed in "Study on Improving the Recovery Rate of L-Lysine by Ion Exchange Method - II. Selection of Resin Ionic State and Decolorization of L-Lysine-Containing Solution" (Journal of Fujian Normal University, 1990) that as the pH value of the fermentation broth decreases, the transmittance after decolorization increases (i.e., the purity of extracted L-lysine increases), but the loss of L-lysine also increases (i.e., the yield of extracted L-lysine decreases); and Li Baozhu disclosed in "Study on Separation and Extraction of Complex Amino Acids from Soybean Meal" (Master's Thesis of Fuzhou University, 2013) that 732 cation exchange resin is used. When ion exchange resins adsorb amino acids, within a solution pH range of 1-7, the adsorption capacity of the complex amino acids decreases as the initial pH decreases. This may be because lower pH values ​​result in more hydrogen ions in the solution, leading to competitive adsorption between the hydrogen ions and amino acids. The amino acids adsorbed onto the resin are then displaced by the excess hydrogen ions in the solution, reducing the equilibrium adsorption capacity of the amino acids on the resin. Alternatively, at lower pH values, amino acids primarily exist in ionic form, and the solid surface in such solutions carries a charge. Due to electrorepulsion, the adsorption degree of amino acid ions on the resin is reduced, making it difficult to simultaneously improve the purity and yield of L-lysine. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a method for extracting L-lysine from fermentation broth, which can simultaneously improve the yield and purity of extracted L-lysine, and the yield of extracted L-lysine is less affected by the residual sugar content in the fermentation broth.

[0011] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for extracting L-lysine from fermentation broth comprises the following steps: ceramic membrane filtration, removal of inorganic salts, ion exchange, activated carbon decolorization, and crystallization. The ceramic membrane filtration process involves passing the L-lysine fermentation broth through a ceramic membrane filtration device for filtration, and collecting the filtrate as the fermentation broth. In the ceramic membrane filtration, the filtration temperature is 63-67℃ and the filtration pressure is 0.28-0.32MPa. The ceramic membrane in the ceramic membrane filtration device has a pore size of 50 nm and a membrane flux of 60 L / (m²). 2 •h); To remove inorganic salts, an ammonium oxalate aqueous solution and a chelating agent are added to the fermentation broth, stirred at room temperature for 40-60 minutes, filtered, and the filtrate is collected as the fermentation broth after removing inorganic salts. The ratio of L-lysine fermentation broth used in the ceramic membrane filtration to the ammonium oxalate aqueous solution and chelating agent used for removing inorganic salts is 2000g:180-200mL:20-21g. In the removal of inorganic salts, the mass concentration of the ammonium oxalate aqueous solution is 4%. The chelating agent is prepared by mixing magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and a first portion of distilled water, stirring at room temperature for 20-30 minutes to obtain a metal salt aqueous solution; stirring a second portion of distilled water at room temperature, then adding the metal salt aqueous solution dropwise, while simultaneously adding sodium carbonate aqueous solution to maintain the pH value at 9.8-10.2; after the addition is complete, heating to 78-82℃ and reacting at 78-82℃ for 22-26 hours; cooling to room temperature, stirring under a nitrogen atmosphere at room temperature, then adding an L-lysine hydrochloride aqueous solution dropwise; after the addition is complete, stirring for 25-30 hours; filtering, washing, and vacuum drying the filter residue; mixing with a third portion of distilled water, stirring at 38-42℃ for 20-30 minutes, heating to 58-62℃, adding sodium tripolyphosphate, stirring for 2-2.5 hours, filtering, washing, and vacuum drying the filter residue to obtain the chelating agent; In the preparation of the chelating agent, the ratio of magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, first part distilled water, second part distilled water, L-lysine hydrochloride aqueous solution, third part distilled water, and sodium tripolyphosphate is 51-51.5g:37.2-37.5g:1980-2020mL:980-1020mL:570-600mL:190-210mL:3-3.2g; The sodium carbonate aqueous solution has a mass concentration of 3%; The mass concentration of the L-lysine hydrochloride aqueous solution is 1%; The dropping rate of the metal salt aqueous solution is 30-40 mL / min; The dropping rate for adding L-lysine hydrochloride aqueous solution is 30-40 mL / min; The ion exchange process involves mixing distilled water and corn starch, gelatinizing at 93-97°C for 30-40 minutes, naturally cooling to room temperature, adding polyethylene glycol 400, stirring at room temperature for 30-60 minutes, mixing with the fermentation broth after removing inorganic salts, stirring at room temperature for 10-20 minutes, adjusting the pH to 1.9-2.1, and passing the mixture into an ion exchange column for adsorption. Ammonia water is used as the eluent and passed into the ion exchange column for desorption. When L-lysine is detected in the effluent, the effluent is collected. When L-lysine is no longer detected in the effluent, elution is stopped, resulting in an eluent containing L-lysine. The ratio of L-lysine fermentation broth used in the ceramic membrane filtration to distilled water, corn starch, and polyethylene glycol 400 used in the ion exchange is 2000g:4080-5020mL:6.5-7g:2.3-2.5g; In the ion exchange process, the resin loading of the ion exchange column is 40L; When adjusting the pH value to 1.9-2.1, use a hydrochloric acid aqueous solution with a concentration of 5.5-6.5 mol / L. The flow rate for adsorption in the ion exchange column is 0.9-1.1 BV / h; The concentration of the ammonia solution is 1.9-2.1 mol / L; The flow rate for desorption in the ion exchange column is 0.45-0.55 BV / h; The ion exchange column is packed with 732 type cation exchange resin. Before packing the 732 type cation exchange resin into the column, pretreatment is required. The pretreatment method is as follows: swell the 732 type cation exchange resin with an average particle size of 0.783 mm using 5 times its volume of distilled water, then wash with distilled water until no floating matter remains; soak in 4 times its volume of 2 mol / L hydrochloric acid aqueous solution for 4 hours, remove the hydrochloric acid solution, and wash with distilled water until neutral; soak in 4 times its volume of 2 mol / L sodium hydroxide aqueous solution for 4 hours, remove the sodium hydroxide solution, and wash with distilled water until neutral; soak in 4 times its volume of 2 mol / L hydrochloric acid aqueous solution for 12 hours, remove the hydrochloric acid solution, and wash with distilled water until neutral. The activated carbon decolorization process involves passing an eluent containing L-lysine into an activated carbon decolorization column for decolorization, and collecting the effluent as the decolorized fermentation broth. In the activated carbon decolorization process, the flow rate for decolorization in the activated carbon decolorization column is 0.9-1.1 BV / h; The activated carbon decolorization column has an activated carbon content of 30L; The activated carbon decolorization column is filled with granular activated carbon. Before packing the granular activated carbon into the column, it needs to be pretreated to improve the decolorization ability of the activated carbon. The pretreatment method is as follows: dry the granular activated carbon with an average particle size of 20-30 mesh at 115-125℃ for 4-4.5h, then mix it with a citric acid aqueous solution with a concentration of 0.58-0.62mol / L at a mass ratio of 1:9-11, stir at room temperature for 2-2.5h, filter, dry at 58-62℃ for 46-50h, cool to room temperature, wash, and dry at 88-92℃ for 22-26h. The crystallization process involves concentrating the decolorized fermentation broth under reduced pressure, adjusting the pH to 4.8-5.2 using hydrochloric acid aqueous solution, cooling to crystallize, separating the crystals, and obtaining L-lysine hydrochloride. In the crystallization process, the concentration under reduced pressure is carried out to 28-32% of the original volume. The concentration of the hydrochloric acid aqueous solution is 5.8-6.2 mol / L; The cooling crystallization temperature is 9-11℃, and the time is 14-16h.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for extracting L-lysine according to the present invention can simultaneously improve the yield and purity of extracted L-lysine, and the yield of extracted L-lysine is less affected by the residual sugar content in the fermentation broth. According to the method of the present invention, when extracting from L-lysine fermentation broth with an L-lysine content of 16.20% by mass and a glucose content of 1.15% by mass, the purity of the obtained L-lysine hydrochloride is 99.82-99.89%, and the extraction yield is 88.3-88.8%. According to the method of the present invention, when extracting from L-lysine fermentation broth with an L-lysine content of 11.28% by mass and a glucose content of 2.17% by mass, the purity of the obtained L-lysine hydrochloride is 99.83-99.90%, and the extraction yield is 87.6-88.2%. Detailed Implementation

[0013] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0014] In Examples 1-3 and Comparative Examples 1-5 of the present invention, room temperature refers to 22±2℃.

[0015] In Examples 1-3 and Comparative Examples 1-5 of the present invention, the L-lysine fermentation broth samples were from the same batch of L-lysine fermentation broth. The method for obtaining the L-lysine fermentation broth was as follows: fermentation was carried out using Corynebacterium glutamicum as the starting strain, glucose as the carbon source, (NH4)2SO4 as the inorganic nitrogen source, and corn steep liquor as the organic nitrogen source. After centrifugation (8000 rpm, 10 min), the supernatant was taken as the L-lysine fermentation broth.

[0016] In Examples 1-3 and Comparative Examples 1-5 of the present invention, the detection method used when detecting transmittance is spectrophotometry.

[0017] In Examples 1-3 and Comparative Examples 1-5 of the present invention, the detection method used to detect the mass content of solids is as follows: Add 10 mL of sample to a pre-weighed dry petri dish, weigh it, and then dry it in an oven at 105℃ until constant weight. Weigh the sample and calculate the percentage of the sample mass after drying to the sample mass before drying. This percentage represents the solid content of the sample.

[0018] In Examples 1-3 and Comparative Examples 1-5 of the present invention, the detection method used to detect the mass content of L-lysine and L-lysine hydrochloride was high performance liquid chromatography; the detection method used to detect the mass content of glucose was anthrone colorimetric method; and the detection method used to detect the mass content of inorganic salts was gravimetric method.

[0019] Example 1 A method for extracting L-lysine from fermentation broth, specifically: Step 1. Ceramic membrane filtration: Take 2000g of L-lysine fermentation broth sample and pass it through a ceramic membrane filtration device for filtration. The filtration temperature is 65℃ and the filtration pressure is 0.3MPa. Collect the filtrate as fermentation broth. The pH of the L-lysine fermentation broth was 7.1, the light transmittance was 57.2%, the water content was 79.52%, and the solid content was 20.48% (L-lysine content was 16.20%, glucose content was 1.15%, inorganic salt content was 2.34%, and other substances content was 0.79%).

[0020] The ceramic membrane in the ceramic membrane filtration device has a pore size of 50 nm and a membrane flux of 60 L / (m²). 2 •h); Step 2. Removal of inorganic salts: Add 180 mL of ammonium oxalate aqueous solution and 20 g of chelating agent to the fermentation broth obtained in Step 1, stir continuously at 200 rpm for 40 min at room temperature, filter, and collect the filtrate as the fermentation broth after removal of inorganic salts. The mass concentration of the ammonium oxalate aqueous solution is 4%; The chelating agent is prepared as follows: 51g of magnesium nitrate hexahydrate, 37.2g of aluminum nitrate nonahydrate, and 2000mL of distilled water are mixed and continuously stirred at 100rpm for 20min at room temperature to obtain an aqueous solution of the metal salt. 1000mL of distilled water is then continuously stirred at 100rpm at room temperature, and the above aqueous solution of the metal salt is added dropwise at a rate of 30mL / min. Simultaneously, an aqueous solution of sodium carbonate is added dropwise to maintain the pH at 10. After the addition is complete, the temperature is raised to 80℃ and reacted at 80℃ for 24h. The mixture is then naturally cooled to room temperature and continuously stirred at 300rpm under a nitrogen atmosphere at room temperature. Finally, 570mL of [amount missing] mL of [amount missing] aqueous solution is added dropwise. The L-lysine hydrochloride aqueous solution was added at a rate of 30 mL / min. After the addition was completed, the mixture was stirred continuously for 25 h. The solution was then filtered, washed twice each with anhydrous ethanol and distilled water, dried under vacuum at 70 °C, and then mixed with 200 mL of distilled water. The mixture was stirred continuously at 100 rpm for 20 min at 40 °C, heated to 60 °C, and 3 g of sodium tripolyphosphate was added. The mixture was stirred continuously for 2 h, filtered, washed twice with distilled water, and dried under vacuum at 70 °C to obtain the chelating agent. The sodium carbonate aqueous solution has a mass concentration of 3%; The mass concentration of the L-lysine hydrochloride aqueous solution is 1%; Step 3. Ion exchange: Mix 5000 mL of distilled water and 6.5 g of corn starch, gelatinize at 95 °C for 30 min, cool naturally to room temperature, add 2.3 g of polyethylene glycol 400, and stir continuously at 200 rpm for 30 min at room temperature. Mix with the fermentation broth obtained in Step 2 after removing inorganic salts, and stir continuously at 200 rpm for 10 min at room temperature. Adjust the pH to 2 using a 6 mol / L hydrochloric acid aqueous solution, and pass it into the ion exchange column at a flow rate of 1 BV / h. Then use a 2 mol / L ammonia solution as the eluent, and pass it into the ion exchange column at a flow rate of 0.5 BV / h. When L-lysine is detected in the effluent (detected by ninhydrin colorimetric reaction), collect the effluent. When L-lysine is no longer detected in the effluent (detected by ninhydrin colorimetric reaction), stop elution to obtain an eluent containing L-lysine. The resin loading of the ion exchange column is 40L; The ion exchange column is packed with 732 type cation exchange resin. Before packing the 732 type cation exchange resin into the column, pretreatment is required. The pretreatment method is as follows: swell the 732 type cation exchange resin with an average particle size of 0.783 mm using 5 times its volume of distilled water, then wash with distilled water until no floating matter remains; soak in 4 times its volume of 2 mol / L hydrochloric acid aqueous solution for 4 hours, remove the hydrochloric acid solution, and wash with distilled water until neutral; soak in 4 times its volume of 2 mol / L sodium hydroxide aqueous solution for 4 hours, remove the sodium hydroxide solution, and wash with distilled water until neutral; soak in 4 times its volume of 2 mol / L hydrochloric acid aqueous solution for 12 hours, remove the hydrochloric acid solution, and wash with distilled water until neutral. Step 4. Activated carbon decolorization: The eluent containing L-lysine obtained in step 3 is passed into an activated carbon decolorization column at a flow rate of 1 BV / h, and the effluent is collected as the decolorized fermentation broth. The activated carbon decolorization column has an activated carbon content of 30L; The activated carbon decolorization column is filled with granular activated carbon. Before packing the granular activated carbon into the column, it needs to be pretreated. The pretreatment method is as follows: the granular activated carbon with an average particle size of 20 mesh is dried at 120°C for 4 hours, and then mixed with a 0.6 mol / L citric acid aqueous solution at a mass ratio of 1:10. The mixture is stirred continuously at 200 rpm for 2 hours at room temperature, filtered, dried at 60°C for 48 hours, naturally cooled to room temperature, washed with distilled water, and then dried at 90°C for 24 hours. Step 5. Crystallization: The decolorized fermentation broth was concentrated under reduced pressure to 30% of its original volume. The pH was adjusted to 5 using a 6 mol / L hydrochloric acid aqueous solution. The mixture was cooled and crystallized at 10°C for 15 hours. The crystals were then separated to obtain L-lysine hydrochloride.

[0021] Example 2 A method for extracting L-lysine from fermentation broth, specifically: Step 1. Ceramic membrane filtration: Take 2000g of L-lysine fermentation broth sample and pass it through a ceramic membrane filtration device for filtration. The filtration temperature is 65℃ and the filtration pressure is 0.3MPa. Collect the filtrate as fermentation broth. The pH of the L-lysine fermentation broth was 7.1, the light transmittance was 57.2%, the water content was 79.52%, and the solid content was 20.48% (L-lysine content was 16.20%, glucose content was 1.15%, inorganic salt content was 2.34%, and other substances content was 0.79%).

[0022] The ceramic membrane in the ceramic membrane filtration device has a pore size of 50 nm and a membrane flux of 60 L / (m²). 2 •h); Step 2. Removal of inorganic salts: Add 200 mL of ammonium oxalate aqueous solution and 21 g of chelating agent to the fermentation broth obtained in Step 1, stir continuously at 200 rpm for 60 min at room temperature, filter, and collect the filtrate as the fermentation broth after removal of inorganic salts; The mass concentration of the ammonium oxalate aqueous solution is 4%; The chelating agent is prepared as follows: 51.5g magnesium nitrate hexahydrate, 37.5g aluminum nitrate nonahydrate, and 2000mL distilled water are mixed and continuously stirred at 300rpm for 30min at room temperature to obtain a metal salt aqueous solution. 1000mL of distilled water is then continuously stirred at 300rpm at room temperature, and the above metal salt aqueous solution is added dropwise at a rate of 40mL / min. Simultaneously, sodium carbonate aqueous solution is added dropwise to maintain the pH at 10. After the addition is complete, the temperature is raised to 80℃ and reacted at 80℃ for 24h. The mixture is then naturally cooled to room temperature and continuously stirred at 500rpm under a nitrogen atmosphere at room temperature. Finally, 600mL of [amount missing] [unit missing] [of water] is added dropwise. The L-lysine hydrochloride aqueous solution was added at a rate of 40 mL / min. After the addition was completed, the mixture was stirred continuously for 30 h. The solution was then filtered, washed three times each with anhydrous ethanol and distilled water, dried under vacuum at 70 °C, and then mixed with 200 mL of distilled water. The mixture was stirred continuously at 300 rpm for 30 min at 40 °C, heated to 60 °C, and 3.2 g of sodium tripolyphosphate was added. The mixture was stirred continuously for 2.5 h, filtered, washed three times with distilled water, and dried under vacuum at 70 °C to obtain the chelating agent. The sodium carbonate aqueous solution has a mass concentration of 3%; The mass concentration of the L-lysine hydrochloride aqueous solution is 1%; Step 3. Ion exchange: Mix 5000 mL of distilled water and 6.5 g of corn starch, gelatinize at 95 °C for 30 min, cool naturally to room temperature, add 2.5 g of polyethylene glycol 400, and stir continuously at 200 rpm for 30 min at room temperature. Mix with the fermentation broth obtained in Step 2 after removing inorganic salts, and stir continuously at 200 rpm for 10 min at room temperature. Adjust the pH to 2 using a 6 mol / L hydrochloric acid aqueous solution, and pass it into the ion exchange column at a flow rate of 1 BV / h. Then use a 2 mol / L ammonia solution as the eluent, and pass it into the ion exchange column at a flow rate of 0.5 BV / h. When L-lysine is detected in the effluent (detected by ninhydrin colorimetric reaction), collect the effluent. When L-lysine is no longer detected in the effluent (detected by ninhydrin colorimetric reaction), stop elution to obtain an eluent containing L-lysine. The resin loading of the ion exchange column is 40L; The ion exchange column is packed with 732 type cation exchange resin. Before packing the 732 type cation exchange resin into the column, pretreatment is required. The pretreatment method is as follows: swell the 732 type cation exchange resin with an average particle size of 0.783 mm using 5 times its volume of distilled water, then wash with distilled water until no floating matter remains; soak in 4 times its volume of 2 mol / L hydrochloric acid aqueous solution for 4 hours, remove the hydrochloric acid solution, and wash with distilled water until neutral; soak in 4 times its volume of 2 mol / L sodium hydroxide aqueous solution for 4 hours, remove the sodium hydroxide solution, and wash with distilled water until neutral; soak in 4 times its volume of 2 mol / L hydrochloric acid aqueous solution for 12 hours, remove the hydrochloric acid solution, and wash with distilled water until neutral. Step 4. Activated carbon decolorization: The eluent containing L-lysine obtained in step 3 is passed into an activated carbon decolorization column at a flow rate of 1 BV / h, and the effluent is collected as the decolorized fermentation broth. The activated carbon decolorization column has an activated carbon content of 30L; The activated carbon decolorization column is filled with granular activated carbon. Before packing the granular activated carbon into the column, it needs to be pretreated. The pretreatment method is as follows: the granular activated carbon with an average particle size of 20 mesh is dried at 120°C for 4 hours, and then mixed with a 0.6 mol / L citric acid aqueous solution at a mass ratio of 1:10. The mixture is stirred continuously at 200 rpm for 2 hours at room temperature, filtered, dried at 60°C for 48 hours, naturally cooled to room temperature, washed with distilled water, and then dried at 90°C for 24 hours. Step 5. Crystallization: The decolorized fermentation broth was concentrated under reduced pressure to 30% of its original volume. The pH was adjusted to 5 using a 6 mol / L hydrochloric acid aqueous solution. The mixture was cooled and crystallized at 10°C for 15 hours. The crystals were then separated to obtain L-lysine hydrochloride.

[0023] Example 3 A method for extracting L-lysine from fermentation broth, specifically: Step 1. Ceramic membrane filtration: Take 2000g of L-lysine fermentation broth sample and pass it through a ceramic membrane filtration device for filtration. The filtration temperature is 65℃ and the filtration pressure is 0.3MPa. Collect the filtrate as fermentation broth. The pH of the L-lysine fermentation broth was 7.1, the light transmittance was 57.2%, the water content was 79.52%, and the solid content was 20.48% (L-lysine content was 16.20%, glucose content was 1.15%, inorganic salt content was 2.34%, and other substances content was 0.79%).

[0024] The ceramic membrane in the ceramic membrane filtration device has a pore size of 50 nm and a membrane flux of 60 L / (m²).2 •h); Step 2. Removal of inorganic salts: Add 200 mL of ammonium oxalate aqueous solution and 21 g of chelating agent to the fermentation broth obtained in Step 1, stir continuously at 200 rpm for 60 min at room temperature, filter, and collect the filtrate as the fermentation broth after removal of inorganic salts; The mass concentration of the ammonium oxalate aqueous solution is 4%; The chelating agent is prepared as follows: 51.5g magnesium nitrate hexahydrate, 37.5g aluminum nitrate nonahydrate, and 2000mL distilled water are mixed and continuously stirred at 300rpm for 30min at room temperature to obtain a metal salt aqueous solution. 1000mL of distilled water is then continuously stirred at 300rpm at room temperature, and the above metal salt aqueous solution is added dropwise at a rate of 40mL / min. Simultaneously, sodium carbonate aqueous solution is added dropwise to maintain the pH at 10. After the addition is complete, the temperature is raised to 80℃ and reacted at 80℃ for 24h. The mixture is then naturally cooled to room temperature and continuously stirred at 500rpm under a nitrogen atmosphere at room temperature. Finally, 600mL of [amount missing] [unit missing] [of water] is added dropwise. The L-lysine hydrochloride aqueous solution was added at a rate of 40 mL / min. After the addition was completed, the mixture was stirred continuously for 30 h. The solution was then filtered, washed three times each with anhydrous ethanol and distilled water, dried under vacuum at 70 °C, and then mixed with 200 mL of distilled water. The mixture was stirred continuously at 300 rpm for 30 min at 40 °C, heated to 60 °C, and 3.2 g of sodium tripolyphosphate was added. The mixture was stirred continuously for 2.5 h, filtered, washed three times with distilled water, and dried under vacuum at 70 °C to obtain the chelating agent. The sodium carbonate aqueous solution has a mass concentration of 3%; The mass concentration of the L-lysine hydrochloride aqueous solution is 1%; Step 3. Ion exchange: Mix 5000 mL of distilled water and 7 g of corn starch, gelatinize at 95 °C for 30 min, cool naturally to room temperature, add 2.5 g of polyethylene glycol 400, and stir continuously at 300 rpm for 60 min at room temperature. Mix with the fermentation broth obtained in Step 2 after removing inorganic salts, and stir continuously at 300 rpm for 20 min at room temperature. Adjust the pH to 2 using a 6 mol / L hydrochloric acid aqueous solution, and pass it into the ion exchange column at a flow rate of 1 BV / h. Then use a 2 mol / L ammonia solution as the eluent, and pass it into the ion exchange column at a flow rate of 0.5 BV / h. When L-lysine is detected in the effluent (detected by ninhydrin colorimetric reaction), collect the effluent. When L-lysine is no longer detected in the effluent (detected by ninhydrin colorimetric reaction), stop elution to obtain an eluent containing L-lysine. The resin loading of the ion exchange column is 40L; The ion exchange column is packed with 732 type cation exchange resin. Before packing the 732 type cation exchange resin into the column, pretreatment is required. The pretreatment method is as follows: swell the 732 type cation exchange resin with an average particle size of 0.783 mm using 5 times its volume of distilled water, then wash with distilled water until no floating matter remains; soak in 4 times its volume of 2 mol / L hydrochloric acid aqueous solution for 4 hours, remove the hydrochloric acid solution, and wash with distilled water until neutral; soak in 4 times its volume of 2 mol / L sodium hydroxide aqueous solution for 4 hours, remove the sodium hydroxide solution, and wash with distilled water until neutral; soak in 4 times its volume of 2 mol / L hydrochloric acid aqueous solution for 12 hours, remove the hydrochloric acid solution, and wash with distilled water until neutral. Step 4. Activated carbon decolorization: The eluent containing L-lysine obtained in step 3 is passed into an activated carbon decolorization column at a flow rate of 1 BV / h, and the effluent is collected as the decolorized fermentation broth. The activated carbon decolorization column has an activated carbon content of 30L; The activated carbon decolorization column is filled with granular activated carbon. Before packing the granular activated carbon into the column, it needs to be pretreated. The pretreatment method is as follows: the granular activated carbon with an average particle size of 20 mesh is dried at 120°C for 4 hours, and then mixed with a 0.6 mol / L citric acid aqueous solution at a mass ratio of 1:10. The mixture is stirred continuously at 200 rpm for 2 hours at room temperature, filtered, dried at 60°C for 48 hours, naturally cooled to room temperature, washed with distilled water, and then dried at 90°C for 24 hours. Step 5. Crystallization: The decolorized fermentation broth was concentrated under reduced pressure to 30% of its original volume. The pH was adjusted to 5 using a 6 mol / L hydrochloric acid aqueous solution. The mixture was cooled and crystallized at 10°C for 15 hours. The crystals were then separated to obtain L-lysine hydrochloride.

[0025] Comparative Example 1 The method for extracting L-lysine from the fermentation broth was basically the same as in Example 1, except that in step 2, removing inorganic salts, 3g of sodium tripolyphosphate was used instead of 20g of chelating agent.

[0026] Comparative Example 2 The method for extracting L-lysine from the fermentation broth is basically the same as in Example 1, except that in step 2, removing inorganic salts, the addition of L-lysine hydrochloride aqueous solution is omitted in the preparation method of the chelating agent. Specifically, the preparation method of the chelating agent is changed to: 51g magnesium nitrate hexahydrate, 37.2g aluminum nitrate nonahydrate, and 2000mL distilled water were mixed and stirred continuously at 100rpm for 20min at room temperature to obtain an aqueous solution of the metal salt. 1000mL distilled water was stirred continuously at 100rpm at room temperature, and the above aqueous solution of the metal salt was added dropwise at a rate of 30mL / min. At the same time, an aqueous solution of sodium carbonate was added dropwise to maintain the pH value at 10. After the addition was completed, the temperature was raised to 80℃ and reacted at 80℃ for 24h. The temperature was then lowered to 60℃, 3g sodium tripolyphosphate was added, and the mixture was stirred continuously at 100rpm for 2h at 60℃. The mixture was filtered, washed twice with distilled water, and dried under vacuum at 70℃ to obtain the chelating agent. The sodium carbonate aqueous solution has a mass concentration of 3%.

[0027] Comparative Example 3 The method for extracting L-lysine from the fermentation broth is basically the same as in Example 1, except that the addition of corn starch is omitted in step 3. Ion exchange. Specifically, step 3. Ion exchange is changed to: Mix 5000 mL of distilled water and 2.3 g of polyethylene glycol 400, and stir continuously at 200 rpm for 30 min at room temperature. Mix with the fermentation broth obtained in step 2 after removing inorganic salts, and stir continuously at 200 rpm for 10 min at room temperature. Adjust the pH to 2 using a 6 mol / L hydrochloric acid aqueous solution, and pass it into an ion exchange column at a flow rate of 1 BV / h. Then use 2 mol / L ammonia water as the eluent, and pass it into the ion exchange column at a flow rate of 0.5 BV / h. When L-lysine is detected in the eluent (by ninhydrin colorimetric reaction), collect the eluent. When L-lysine is no longer detected in the eluent (by ninhydrin colorimetric reaction), stop elution to obtain an eluent containing L-lysine.

[0028] Comparative Example 4 The method for extracting L-lysine from the fermentation broth is basically the same as in Example 1, except that in step 3. Ion exchange, the addition of polyethylene glycol 400 is omitted. Specifically, step 3. Ion exchange is changed to: Mix 5000 mL of distilled water and 6.5 g of corn starch, gelatinize at 95 °C for 30 min, cool naturally to room temperature, and mix with the fermentation broth obtained in step 2 after removing inorganic salts. Stir continuously at 200 rpm for 10 min at room temperature. Adjust the pH to 2 using a 6 mol / L hydrochloric acid aqueous solution and pass it into an ion exchange column at a flow rate of 1 BV / h. Then, use 2 mol / L ammonia water as the eluent and pass it into the ion exchange column at a flow rate of 0.5 BV / h. When L-lysine is detected in the eluent (by ninhydrin colorimetric reaction), collect the eluent. When L-lysine is no longer detected in the eluent (by ninhydrin colorimetric reaction), stop elution to obtain an eluent containing L-lysine.

[0029] Comparative Example 5 The method for extracting L-lysine from the fermentation broth is basically the same as in Example 1, except that in step 3. Ion exchange, the addition of corn starch and polyethylene glycol 400 is omitted. Specifically, step 3. Ion exchange is changed to: Mix 5000 mL of distilled water with the fermentation broth obtained in step 2 after removing inorganic salts, and stir continuously at 200 rpm for 10 min at room temperature. Adjust the pH to 2 using a 6 mol / L hydrochloric acid aqueous solution and pass it into an ion exchange column at a flow rate of 1 BV / h. Then, use 2 mol / L ammonia water as the eluent and pass it into the ion exchange column at a flow rate of 0.5 BV / h. When L-lysine is detected in the eluent (by ninhydrin colorimetric reaction), collect the eluent. When L-lysine is no longer detected in the eluent (by ninhydrin colorimetric reaction), stop elution to obtain an eluent containing L-lysine.

[0030] Results and Analysis The purity of L-lysine hydrochloride obtained in Examples 1-3 and Comparative Examples 1-5 was tested, and the mass of L-lysine hydrochloride obtained was counted. After converting the mass of L-lysine in the L-lysine fermentation broth into the mass of L-lysine hydrochloride (2000g×16.20%×182.65 / 146.19), the extraction yield was calculated. The final results are shown in Table 1. Table 1

[0031] Furthermore, to verify the extraction efficiency of the methods in Examples 1-3 and Comparative Examples 1-5 for L-lysine fermentation broth with high residual sugar content, another batch of L-lysine fermentation broth was used for testing. The indicators of the L-lysine fermentation broth are as follows: The pH value of the L-lysine fermentation broth was 7.0, the light transmittance was 61.4%, the water content was 83.20%, and the solid content was 16.80% (L-lysine content was 11.28%, glucose content was 2.17%, inorganic salt content was 2.51%, and other substances content was 0.84%).

[0032] Then, after extracting L-lysine according to the methods of Examples 1-3 and Comparative Examples 1-5, the purity, mass, and calculated extraction yield of the obtained L-lysine hydrochloride are shown in Table 2: Table 2

[0033] After comparing the extraction results of Comparative Examples 1-5 with those of Example 1, it was found that the purity and extraction yield of L-lysine obtained by the methods of Comparative Examples 1-2 were lower than those of the method of Example 1, but the extraction results were less affected by the glucose content in the L-lysine fermentation broth; the purity and extraction yield of L-lysine obtained by the methods of Comparative Examples 3-5 were also lower than those of the method of Example 1, and the extraction results were less affected by the glucose content in the L-lysine fermentation broth.

[0034] Analysis revealed that the methods of Comparative Examples 1-2 differed from those of Example 1 primarily in the addition of the chelating agent and the preparation method of the chelating agent. In Example 1, a chelating agent was added. Specifically, in the preparation of the chelating agent, magnesium aluminum hydrotalcite was first synthesized. Then, following the method disclosed by Guo Junqing et al. in "Preparation and Characterization of L-Lysine Intercalated Hydrotalcite-Montmorillonite Composite" (New Chemical Materials, 2018), L-lysine was used for intercalation. Following the method disclosed by Xu Sheng et al. in "Surface Modification and Mechanism of Magnesium Aluminum Hydrotalcite Flame Retardant" (Journal of the Chinese Ceramic Society, 2013), sodium tripolyphosphate was introduced onto its surface to obtain the chelating agent. The L-lysine in the chelating agent increased the binding amount of sodium tripolyphosphate, preventing the introduction of impurities during chelation and thus improving the chelation effect of sodium tripolyphosphate. Sodium tripolyphosphate could chelate calcium and magnesium ions onto the surface of magnesium aluminum hydrotalcite, thereby improving the removal effect of calcium and magnesium ions and avoiding subsequent impact on ion exchange. The difference between the methods in Comparative Examples 3-4 and those in Example 1 lies in the addition of corn starch and polyethylene glycol 400 during ion exchange. In the method of Example 1, corn starch and polyethylene glycol 400 were used simultaneously during ion exchange. The addition of these components was based on the principles described in Wang Zihan's "The Influence of Sugars and Sugar Alcohols on the Gelatinization and Retrogradation Characteristics of Starch in Grain Crops with Different Molecular Structures" (Master's Thesis, Yangzhou University, 2025). Starch interacts with glucose, thus reducing the influence of glucose. Furthermore, starch hydrolysis can adsorb hydrogen ions, thereby avoiding the influence of hydrogen ions. The method also referenced Yan Husheng's "Multiple Non-Covalent Interactions and Their Synergistic Effects in Adsorption..." The principles of polyethylene glycol 400 in applications such as separation and controlled release of drugs (Polymer Bulletin, 2013), Li Baozhu's study on the separation and extraction of complex amino acids from soybean meal (Master's thesis, Fuzhou University, 2013), and Li Wei et al.'s study on the influence of polyethylene glycol molecular weight and dosage on the properties of starch slurry film (Journal of Anhui University of Technology, 2018) suggest that there is a hydrogen bond between polyethylene glycol 400 and starch, which weakens the degree of directional aggregation between starch molecules, promotes the dispersion of starch, and helps starch to play a better role. Polyethylene glycol 400 can also act as a surfactant to promote the binding of hydrophobic groups of L-lysine with cation exchange resin, further reducing the influence of glucose concentration and hydrogen ions.

[0035] Compared with the method of Comparative Example 5, the difference lies in the simultaneous addition of corn starch and polyethylene glycol 400 during ion exchange. Comparing the results of Comparative Examples 3-5 with those of Example 1, the sum of the total differences in extraction yield between Comparative Examples 3 and 4 and Example 1 is greater than the difference in extraction yield between Comparative Example 5 and Example 1. After changing the glucose concentration, the sum of the decreases in extraction yield between Comparative Examples 3 and 4 is greater than the decrease in extraction yield between Comparative Example 5, indicating that there is a certain synergistic effect between starch and polyethylene glycol 400. Analysis suggests that this may be related to the fact that polyethylene glycol 400 can promote starch dispersion and that starch can enhance the promoting effect of polyethylene glycol 400.

Claims

1. A method for extracting L-lysine from fermentation broth, characterized in that, It consists of the following steps: ceramic membrane filtration, removal of inorganic salts, ion exchange, activated carbon decolorization, and crystallization; The ceramic membrane filtration process involves passing the L-lysine fermentation broth through a ceramic membrane filtration device for filtration, and collecting the filtrate as the fermentation broth. To remove inorganic salts, an ammonium oxalate aqueous solution and a chelating agent are added to the fermentation broth, stirred at room temperature, filtered, and the filtrate is collected as the fermentation broth after removing inorganic salts. The chelating agent is prepared by mixing magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and a first portion of distilled water, stirring to obtain an aqueous solution of the metal salt; stirring a second portion of distilled water, adding the aqueous solution of the metal salt dropwise, and adding an aqueous solution of sodium carbonate dropwise to maintain the pH value at 9.8-10.

2. After the dropwise addition is completed, reacting at 78-82℃ under a nitrogen atmosphere, stirring, adding an aqueous solution of L-lysine hydrochloride dropwise, stirring, filtering, washing, and vacuum drying the filter residue, mixing with a third portion of distilled water, stirring at 38-42℃, heating to 58-62℃, adding sodium tripolyphosphate, stirring, filtering, washing, and vacuum drying the filter residue to obtain the chelating agent. The ion exchange process involves mixing distilled water and corn starch, gelatinizing the mixture at 93-97°C, cooling it, adding polyethylene glycol 400, stirring, mixing it with the fermentation broth after removing inorganic salts, stirring, adjusting the pH to 1.9-2.1, and passing it through an ion exchange column for adsorption. Ammonia water is used as the eluent and passed through the ion exchange column for desorption. The effluent is collected to obtain an eluent containing L-lysine.

2. The method for extracting L-lysine from fermentation broth according to claim 1, characterized in that, In the ceramic membrane filtration, the filtration temperature is 63-67℃ and the filtration pressure is 0.28-0.32MPa. The ceramic membrane in the ceramic membrane filtration device has a pore size of 50 nm and a membrane flux of 60 L / (m²). 2 •h).

3. The method for extracting L-lysine from fermentation broth according to claim 1, characterized in that, The ratio of L-lysine fermentation broth used in the ceramic membrane filtration to the ammonium oxalate aqueous solution and chelating agent used for removing inorganic salts is 2000g:180-200mL:20-21g. In the process of removing inorganic salts, the mass concentration of the ammonium oxalate aqueous solution is 4%.

4. The method for extracting L-lysine from fermentation broth according to claim 1, characterized in that, In the preparation of the chelating agent, the ratio of magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, first part distilled water, second part distilled water, L-lysine hydrochloride aqueous solution, third part distilled water, and sodium tripolyphosphate is 51-51.5g:37.2-37.5g:1980-2020mL:980-1020mL:570-600mL:190-210mL:3-3.2g.

5. The method for extracting L-lysine from fermentation broth according to claim 1, characterized in that, In the preparation of the chelating agent, the mass concentration of the sodium carbonate aqueous solution is 3%; The mass concentration of the L-lysine hydrochloride aqueous solution is 1%; The dropping rate of the metal salt aqueous solution is 30-40 mL / min; The dropping rate for adding L-lysine hydrochloride aqueous solution is 30-40 mL / min.

6. The method for extracting L-lysine from fermentation broth according to claim 1, characterized in that, The ratio of L-lysine fermentation broth used in the ceramic membrane filtration to distilled water, corn starch, and polyethylene glycol 400 used in the ion exchange is 2000g:4080-5020mL:6.5-7g:2.3-2.5g.

7. The method for extracting L-lysine from fermentation broth according to claim 1, characterized in that, In the ion exchange process, the resin loading of the ion exchange column is 40L; When adjusting the pH value to 1.9-2.1, use a hydrochloric acid aqueous solution with a concentration of 5.5-6.5 mol / L. The flow rate for adsorption in the ion exchange column is 0.9-1.1 BV / h; The concentration of the ammonia solution is 1.9-2.1 mol / L; The flow rate for desorption in the ion exchange column is 0.45-0.55 BV / h.

8. The method for extracting L-lysine from fermentation broth according to claim 1, characterized in that, In the ion exchange process, the ion exchange column is packed with 732 type cation exchange resin. Before packing the 732 type cation exchange resin into the column, pretreatment is required. The pretreatment method is as follows: swell the 732 type cation exchange resin with an average particle size of 0.783 mm using 5 times its volume of distilled water, then wash it with distilled water until no floating matter remains; soak it in 4 times its volume of 2 mol / L hydrochloric acid aqueous solution for 4 hours, remove the hydrochloric acid aqueous solution, and wash it with distilled water until neutral. Soak for 4 hours with 4 times the volume of a 2 mol / L sodium hydroxide aqueous solution, remove the sodium hydroxide aqueous solution, and wash with distilled water until neutral; Soak for 12 hours with 4 times the volume of 2 mol / L hydrochloric acid solution, remove the hydrochloric acid solution, and wash with distilled water until neutral.

9. The method for extracting L-lysine from fermentation broth according to claim 1, characterized in that, The activated carbon decolorization process involves passing an eluent containing L-lysine into an activated carbon decolorization column for decolorization, and collecting the effluent as the decolorized fermentation broth. In the activated carbon decolorization process, the flow rate for decolorization in the activated carbon decolorization column is 0.9-1.1 BV / h; The activated carbon decolorization column has an activated carbon content of 30L; The activated carbon decolorization column is filled with granular activated carbon. Before packing the granular activated carbon into the column, it needs to be pretreated. The pretreatment method is as follows: the granular activated carbon with an average particle size of 20-30 mesh is dried at 115-125℃, then mixed with a citric acid aqueous solution with a concentration of 0.58-0.62mol / L at a mass ratio of 1:9-11, stirred, filtered, dried at 58-62℃, cooled to room temperature, washed, and dried at 88-92℃.

10. The method for extracting L-lysine from fermentation broth according to claim 1, characterized in that, The crystallization process involves concentrating the decolorized fermentation broth under reduced pressure, adjusting the pH to 4.8-5.2 using hydrochloric acid aqueous solution, cooling to crystallize, separating the crystals, and obtaining L-lysine hydrochloride. In the crystallization process, the concentration under reduced pressure is carried out to 28-32% of the original volume. The concentration of the hydrochloric acid aqueous solution is 5.8-6.2 mol / L; The cooling crystallization temperature is 9-11℃, and the time is 14-16h.

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