A method for recovering glutamic acid, ammonium sulfate and pyroglutamic acid from an isoelectric mother liquor of glutamic acid

Abstract

This invention relates to the field of biochemical technology, specifically to a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor containing glutamic acid. The method includes: crystallizing and separating ammonium sulfate and a secondary mother liquor from an isoelectric mother liquor containing no bacteria; chromatographically separating the secondary mother liquor to obtain a first eluent containing pyroglutamic acid and ammonium sulfate and a second eluent containing glutamic acid; precipitating and separating the ammonium sulfate and pyroglutamic acid in the first eluent using an organic solvent; and separating glutamic acid from the second eluent. This method can simultaneously obtain three products: glutamic acid, pyroglutamic acid, and ammonium sulfate, while ensuring high yields and purity of all three products. It offers advantages such as mild conditions, low energy consumption, and low cost, enabling industrial-scale production and possessing significant practical application value.

Description

Technical Field

[0001] This invention relates to the field of biochemical technology, specifically to a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid. Background Technology

[0002] The isoelectric mother liquor of glutamic acid is the waste liquid produced after isoelectric crystallization and centrifugation during the extraction of glutamic acid. Its main components are glutamic acid, ammonium sulfate, pyroglutamic acid, bacterial protein, and pigments. The composition of the isoelectric mother liquor varies slightly depending on the glutamic acid extraction process. Currently, commonly used isoelectric crystallization processes include the room temperature isoelectric point process (30℃), the low temperature isoelectric point process (0-4℃), and the bacterial-concentrated isoelectric point process. The glutamic acid content in the isoelectric mother liquor is between 2% and 4%, the ammonium sulfate content in the unconcentrated isoelectric mother liquor is between 3% and 6%, and the ammonium sulfate content in the concentrated isoelectric mother liquor is between 8% and 14%. Typically, the pyroglutamic acid content in glutamic acid fermentation broth is low, around 3% of the total glutamic acid content. However, as the extraction process progresses, the pyroglutamic acid content gradually increases: during the glutamic acid concentration stage, due to water shortage and prolonged heating, glutamic acid undergoes dehydration and cyclization to form pyroglutamic acid; during the isoelectric stage, the addition of a large amount of acid releases a large amount of heat, further increasing the pyroglutamic acid content. The pyroglutamic acid content in the concentrated isoelectric mother liquor is between 1% and 3%.

[0003] 2-Pyrrolidone-5-carboxylic acid (PCA), also known as 5-carboxypyrrolidone, oxidized proline, or 2-pyrrolidone-5-carboxylic acid, has the molecular formula C5H7NO3, a molecular weight of 129.11, and an isoelectric point of 0.94. Pyroglutamic acid is a cyclic amino acid that can be generated as an intermediate in amino acid metabolism and transport via enzymatic reactions. It is also a component of many important peptides and proteins in the biosynthesis of proteins, and therefore has wide applications in the daily chemical and pharmaceutical industries. Glutamic acid and pyroglutamic acid can interconvert: glutamic acid undergoes dehydration and cyclization under prolonged heating to form pyroglutamic acid, and pyroglutamic acid hydrolyzes under acidic or alkaline conditions to regenerate glutamic acid. The reaction equations are as follows: Figure 1 As shown.

[0004] Currently, the monosodium glutamate (MSG) industry mainly treats the isoelectric mother liquor of glutamic acid by flocculation and precipitation to extract microbial protein, concentration and crystallization to precipitate ammonium sulfate, and then concentrates and spray-dries the mother liquor to prepare bio-organic fertilizer. However, glutamic acid and pyroglutamic acid in the isoelectric mother liquor are not recovered and utilized, resulting in low glutamic acid extraction yield and waste of valuable resources. Most current research still focuses on how to recover glutamic acid from the mother liquor: Patents CN110372527A and CN110437088A disclose a method for recovering glutamic acid from concentrated isoelectric mother liquor and glutamic acid isoelectric mother liquor. The concentrated isoelectric mother liquor of glutamic acid is treated by ultrafiltration membrane treatment, activated carbon decolorization, electrodialysis treatment, evaporation concentration, cooling crystallization and centrifugation separation to obtain glutamic acid crystals. Some studies have also explored converting pyroglutamic acid in isoelectric mother liquor into glutamic acid or converting glutamic acid into pyroglutamic acid for recycling: The paper "Removal of Pyroglutamic Acid from Glutamic Acid Mother Liquor by Sulfuric Acid Hydrolysis" investigated the optimal hydrolysis conditions for pyroglutamic acid using sulfuric acid hydrolysis; CN104177269A discloses a method for separating L-glutamic acid and L-pyroglutamic acid from L-glutamate refining mother liquor. This method primarily involves concentrating and crystallizing the L-glutamate refining mother liquor obtained after redissolving, recrystallizing, and repeatedly reusing crude glutamate to obtain glutamic acid. Subsequently, the secondary mother liquor is subjected to a coking reaction to convert the glutamic acid into pyroglutamic acid, followed by concentration and crystallization to obtain pyroglutamic acid. Although some glutamic acid or pyroglutamic acid can be recycled through interconversion, the conversion process requires high temperature or high pressure reaction conditions, resulting in large equipment investment and high energy consumption. Furthermore, because complete conversion cannot be achieved, glutamic acid and pyroglutamic acid cannot be completely separated, leading to low product purity. Summary of the Invention

[0005] The purpose of this invention is to provide a method for recovering glutamic acid, ammonium sulfate and pyroglutamic acid from an isoelectric mother liquor of glutamic acid.

[0006] This invention, through extensive analysis of the resource-recoverable products and impurities and their characteristics in glutamic acid isoelectric mother liquor, has developed a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from the isoelectric mother liquor via stepwise processing. Compared with existing methods that recover glutamic acid separately or recover glutamic acid and ammonium sulfate separately, this invention not only systematically recovers glutamic acid, ammonium sulfate, and pyroglutamic acid through a unified method, but also achieves higher yields and purities of glutamic acid, ammonium sulfate, and pyroglutamic acid, demonstrating significant practical application value.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] This invention provides a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor containing glutamic acid. The method includes: separating ammonium sulfate and a secondary mother liquor by crystallization from an isoelectric mother liquor containing no bacteria; separating the secondary mother liquor by chromatography to obtain a first eluent containing pyroglutamic acid and ammonium sulfate and a second eluent containing glutamic acid; separating the ammonium sulfate and pyroglutamic acid in the first eluent by precipitation with an organic solvent; and separating glutamic acid from the second eluent.

[0009] In the process of substance separation and extraction, although multi-step extraction and purification can better ensure the purity of the target substance, it often has an adverse effect on the yield. Maintaining both the yield and purity of different target substances simultaneously is particularly difficult in the recovery of multiple target substances. This invention uses glutamic acid, ammonium sulfate, and pyroglutamic acid as target recoveries. Extensive trials were conducted on the recovery sequence and extraction methods for these target substances. It was found that the following recovery process—namely, recovering most of the ammonium sulfate from the isoelectric mother liquor of glutamic acid through crystallization, then separating the pyroglutamic acid and ammonium sulfate from glutamic acid using chromatographic separation techniques, and finally separating the pyroglutamic acid and ammonium sulfate through organic solvent treatment—can significantly improve the yield and purity of glutamic acid, ammonium sulfate, and pyroglutamic acid simultaneously while employing relatively simple separation and extraction steps.

[0010] In the methods described above, the chromatographic separation preferably uses an ammonium-type strong acid cation exchange resin, with 2-4% ammonia water as the eluent.

[0011] Preferably, the eluent is 2-3% ammonia.

[0012] This invention reveals that using an ammonium-type strong acid cation exchange resin is more advantageous for separating pyroglutamic acid and ammonium sulfate from glutamic acid. When used in conjunction with this resin, 2-4% ammonia water as the eluent provides significantly better separation of pyroglutamic acid and ammonium sulfate from glutamic acid compared to other eluents. Simultaneously, it effectively removes other impurities from the isoelectric mother liquor, improving the purity of the target analyte.

[0013] Preferably, the ammonium-type strong acid cation exchange resin is 732 ammonium-type strong acid cation exchange resin, D001 ammonium-type strong acid cation exchange resin, JK008 ammonium-type strong acid cation exchange resin, WA-2 ammonium-type strong acid cation exchange resin, or D61 ammonium-type strong acid cation exchange resin.

[0014] All of the above-mentioned ammonium-type strong acid cation exchange resins are commercially available.

[0015] In the above method, the first eluent is fast component A containing pyroglutamic acid and ammonium sulfate. Since pyroglutamic acid is uncharged near its isoelectric point, ammonium sulfate does not undergo ion exchange with the ammonium-type cation exchange resin, and both will elute from the chromatographic column first. The second eluent is slow component B containing glutamic acid. Since glutamic acid is positively charged at pH 0.8–1.2, it undergoes ion exchange with the ammonium-type cation exchange resin. Subsequently, as the pH increases with ammonia elution, glutamic acid becomes uncharged and elutes from the resin. Ammonium ions then re-adsorb onto the resin, completing resin regeneration.

[0016] Under the above-mentioned resin and eluent conditions, the preferred temperature for chromatographic separation is 25–30°C.

[0017] The above chromatographic separation preferably uses a simulated moving bed continuous chromatographic separation system, with a preferred feed flow rate of 10-16 mL / min, an eluent flow rate of 22-36 mL / min, and a resin column rotation time of 5-7 min / column.

[0018] The number of resin columns in a simulated moving bed continuous chromatography separation system is preferably 15 to 25.

[0019] Preferably, before chromatographic separation, the secondary mother liquor is first decolorized to obtain a decolorized solution, and the pH of the decolorized solution is adjusted to 0.8-1.2 before chromatographic separation.

[0020] For the decolorization treatment method, activated carbon is preferably used to decolorize the secondary mother liquor, and the decolorized liquid is obtained by filtration.

[0021] Preferably, monosodium glutamate-specific charcoal (preferably added at a rate of 2-3%) is used to decolorize the secondary mother liquor. The decolorization conditions are 50-55℃ for 30-60 minutes (preferably 40-50 minutes), and then plate and frame filtration is used to obtain the decolorized liquid.

[0022] The first eluent obtained by the above chromatographic separation is processed to separate ammonium sulfate and pyroglutamic acid. The specific method includes: firstly evaporating and drying the first eluent to obtain a crude mixture of pyroglutamic acid and ammonium sulfate, then mixing the crude product with an organic solvent, separating it to obtain ammonium sulfate and a clear liquid, and then concentrating and crystallizing the clear liquid to obtain pyroglutamic acid.

[0023] The organic solvent used in the above separation is one that can separate pyroglutamic acid and ammonium sulfate by utilizing their different solubilities in the organic solvent. After mixing the crude mixture of pyroglutamic acid and ammonium sulfate with the organic solvent, the two are separated by the fact that one of the two substances is soluble in the organic solvent while the other is insoluble.

[0024] Among organic solvents that meet the above requirements, ethanol (anhydrous ethanol) is preferred for the separation of pyroglutamic acid and ammonium sulfate. Since ammonium sulfate is insoluble in ethanol, it is obtained through solid-liquid separation (e.g., filtration) and drying, while pyroglutamic acid is present in the resulting supernatant. The supernatant is then concentrated and crystallized to obtain pyroglutamic acid. Using ethanol for separation better ensures both the yield and purity of ammonium sulfate and pyroglutamic acid.

[0025] After the above ethanol precipitation separation, the purity of the ammonium sulfate obtained can reach 94-96%, and the yield can reach 92-96%. The purity of the pyroglutamic acid can reach 96-98.5%, and the yield can reach 90-95%.

[0026] The preferred conditions for pyroglutamic acid concentration and crystallization are: concentration temperature 55-65℃, vacuum degree -0.08--0.09MPa, concentration to 1 / 6-1 / 8 of the original volume, and crystallization temperature 10-15℃.

[0027] The yield of glutamic acid in the second eluent obtained by the above chromatographic separation can reach 94-98%, and the purity can reach 90-95%. Glutamic acid can be separated from the second eluent by methods such as crystallization. Preferably, the second eluent is reused in an isoelectric crystallization apparatus for glutamic acid crystallization.

[0028] The preferred crystallization method is isoelectric pull-cool crystallization, adjusting the pH to 3.2-3.3 with concentrated sulfuric acid, cooling to 10-12℃ (cooling water or other methods can be used), and crystallizing for 2-6 hours.

[0029] In the methods described above, the concentration crystallization method is preferred for the crystallization of ammonium sulfate. The specific conditions are as follows: the isoelectric mother liquor of glutamic acid without bacteria is continuously concentrated to 45-50 Baumé under the conditions of 70-80℃ and vacuum degree of -0.08 to -0.09 MPa, and then subjected to cooling crystallization at a cooling rate of 3-5℃ / h, a crystallization temperature of 20-25℃, and a crystallization time of 4-6h.

[0030] The ammonium sulfate obtained through the above crystallization steps has a purity of 82-87% and a yield of 60-65%.

[0031] In this invention, the concentration of glutamic acid in the bacterial-free glutamic acid isoelectric mother liquor is ≥10g / L, the concentration of pyroglutamic acid is ≥5g / L, and the concentration of ammonium sulfate is ≥20g / L.

[0032] Preferably, the concentration of glutamic acid in the isoelectric mother liquor containing no bacteria is ≥15 g / L (more preferably ≥20 g / L, even more preferably 20-40 g / L), the concentration of pyroglutamic acid is greater than 5 g / L (more preferably ≥8 g / L, even more preferably 8-20 g / L), and the concentration of ammonium sulfate is greater than 20 g / L (more preferably ≥30 g / L, even more preferably ≥50 g / L, even more preferably 100-150 g / L).

[0033] The method of the present invention can directly use the isoelectric mother liquor of glutamic acid without bacteria, or it can use the isoelectric mother liquor containing bacteria, and then filter out the bacteria to obtain the isoelectric mother liquor of glutamic acid without bacteria.

[0034] For isoelectric mother liquor raw materials containing bacteria, the method for removing bacteria includes: filtering the isoelectric mother liquor containing bacteria through a ceramic membrane to remove bacteria. The ceramic membrane has a pore size of 50-200 nm, an inlet pressure of 0.2-0.3 MPa (more preferably 0.2-0.25 MPa), a temperature of 50-60 °C, and a circulation flow rate of 2-5 m³ / h. 3 / h (more preferably 3-4m) 3 / h), with an outlet pressure of 0.10 to 0.15 MPa (more preferably 0.13 to 0.15 MPa).

[0035] During ceramic membrane filtration, when the volume of the retentate drops to 15-20% of the initial volume, water is added for dialysis. When the concentration of glutamic acid in the dialysate is less than 2 g / L, dialysis is stopped. The resulting dialysate is the isoelectric mother liquor of glutamic acid without bacteria.

[0036] The present invention also provides the application of the above-described method for recovering glutamic acid, ammonium sulfate and pyroglutamic acid from glutamic acid isoelectric mother liquor in the resource utilization treatment of glutamic acid production waste liquid.

[0037] The beneficial effects of this invention are as follows: The method provided by this invention can simultaneously obtain three products: glutamic acid, pyroglutamic acid, and ammonium sulfate, and can simultaneously ensure that glutamic acid, pyroglutamic acid, and ammonium sulfate all have high yields and purity; the method uses chromatographic separation technology to separate glutamic acid from pyroglutamic acid and ammonium sulfate, the separation conditions are mild, the energy consumption is low, and the isoelectric mother liquor is filtered to remove bacterial cells and proteins before chromatographic separation, and then concentrated and salted out to remove most of the ammonium sulfate, which can reduce the impact of bacterial adsorption on the resin and reduce the chromatographic separation load, save equipment investment, realize industrial production, and has good practical application value. Attached Figure Description

[0038] Figure 1 The equation for the interconversion of pyroglutamic acid and glutamic acid in the background technology of this invention is shown below.

[0039] Figure 2This is a process flow diagram of the production process for recovering glutamic acid, ammonium sulfate and pyroglutamic acid from the isoelectric mother liquor of glutamic acid in Example 1 of the present invention.

[0040] Figure 3 This is a schematic diagram of the simulated moving bed continuous chromatography system in Embodiment 1 of the present invention. Detailed Implementation

[0041] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0042] In the following examples, the glutamic acid content was determined using a biosensor SBA-40C; the pyroglutamic acid content was determined using high performance liquid chromatography (HPLC) according to GB / T 35799-2018; the ammonium sulfate content was determined by converting the free ammonium nitrogen content using a nitrogen analyzer according to GB / T22923-2008; and the transmittance was determined using a spectrophotometer.

[0043] In the following examples, the isoelectric mother liquor of glutamic acid was derived from the isoelectric concentration process using bacteria (referencing the *Monopolysaccharide Industry Handbook*). First, a temperature-sensitive *Corynebacterium glutamicum* strain was used for seed culture. Then, the seed liquor was transferred to a fermentation medium for fermentation, with the culture temperature controlled at 33-37°C, pH 7.0, and DO 10-30%, for 30-36 hours. The fermentation broth was then continuously concentrated in a multi-effect evaporator until the glutamic acid concentration reached 30%. Concentrated sulfuric acid was continuously added to the concentrated broth to adjust the pH to 3.2-3.3, followed by a gradient cooling process, with the temperature lowered to 12°C for crystallization for 5 hours. Finally, a centrifuge was used to separate the glutamic acid and the isoelectric mother liquor. The isoelectric mother liquor mainly contains bacterial protein, glutamic acid, pyroglutamic acid, and ammonium sulfate.

[0044] Example 1

[0045] This embodiment provides a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid (flow diagram shown below). Figure 2 As shown), it includes the following steps:

[0046] (1) Take 100L of isoelectric stock solution of glutamic acid, in which the concentration of glutamic acid is 20g / L, the concentration of pyroglutamic acid is 10g / L, and the concentration of ammonium sulfate is 100g / L. Use ceramic membrane filtration for sterilization. The membrane pore size is 50nm, the inlet pressure is 0.2MPa, the temperature is 50℃, and the circulation flow rate is 4m³ / h. 3 / h, outlet pressure 0.13Mpa, when the retentate volume drops to one-fifth of the initial volume, water is added for dialysis, the glutamate concentration in the dialysate is detected, and dialysis is stopped when the glutamate concentration is less than 2g / L;

[0047] (2) The dialysate was pumped into a falling film evaporator for continuous concentration at a concentration temperature of 70°C and a vacuum of -0.09 MPa until it reached 45 Baume. Then it was transferred to a crystallizer for cooling and crystallization at a controlled cooling rate of 5°C / h until it reached 20°C for 4 hours. After that, ammonium sulfate and secondary mother liquor were obtained by centrifugation. The purity of ammonium sulfate was 86% and the yield was 60%.

[0048] (3) Add 2% MSG-specific charcoal to the secondary mother liquor, decolorize at 50℃ for 40 min, and then filter through a plate and frame filter to obtain the decolorized liquor;

[0049] (4) The decolorizing solution was adjusted to pH 0.9 with sulfuric acid before being introduced into a simulated moving bed continuous chromatography system (see schematic diagram). Figure 3 As shown), the system contains 20 chromatographic columns, uses 732 ammonium type strong acid cation exchange resin for separation, separation temperature is 25℃, feed flow rate is 10mL / min, elution is performed with 2% ammonia water, eluent flow rate is 22mL / min, and resin column rotation time is 6min / column.

[0050] (5) Collect the first eluent (fast component A), which mainly contains pyroglutamic acid and ammonium sulfate; evaporate the water and then dry to obtain the crude product. Dissolve the crude product in anhydrous ethanol. Ammonium sulfate is insoluble in anhydrous ethanol. Filter and dry to obtain ammonium sulfate. The purity of ammonium sulfate reaches 94% and the yield is 95%. The clear liquid is concentrated by distillation. The vacuum degree is controlled at -0.08 MPa and the distillation temperature is 65℃. The liquid is concentrated to 1 / 8 of the initial volume. The liquid is cooled to 10℃ to crystallize. Centrifuge and dry to obtain pure pyroglutamic acid. The purity of pyroglutamic acid reaches 96% and the yield reaches 94%.

[0051] (6) Collect the second eluent (slow component B), in which the purity of glutamic acid is 95% and the yield is 94%, and reuse it in the isoelectric crystallizer.

[0052] Example 2

[0053] This embodiment provides a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid, comprising the following steps:

[0054] (1) Take 100L of isoelectric stock solution of glutamic acid, in which the concentration of glutamic acid is 35g / L, the concentration of pyroglutamic acid is 12g / L, and the concentration of ammonium sulfate is 150g / L. Use ceramic membrane filtration for sterilization. The membrane pore size is 100nm, the inlet pressure is 0.25MPa, the temperature is 60℃, and the circulation flow rate is 3m³ / h. 3 / h, outlet pressure 0.15Mpa, when the retentate volume drops to one-fifth of the initial volume, water is added for dialysis, the glutamate concentration in the dialysate is detected, and dialysis is stopped when the glutamate concentration is less than 2g / L;

[0055] (2) The dialysate was pumped into a falling film evaporator for continuous concentration at a concentration temperature of 80°C and a vacuum of -0.09 MPa. It was concentrated to 50 Baume', and then transferred to a crystallizer for cooling and crystallization. The cooling rate was controlled at 4°C / h. The crystals were grown at 20°C for 6 hours. After that, ammonium sulfate and secondary mother liquor were obtained by centrifugation. The purity of ammonium sulfate was 82% and the yield was 65%.

[0056] (3) Add 3% MSG-specific charcoal to the secondary mother liquor, decolorize at 50℃ for 50 min, and then filter through a plate and frame filter to obtain the decolorized liquor;

[0057] (4) The decolorizing solution was adjusted to pH 1.0 with sulfuric acid and then entered a simulated moving bed continuous chromatography system. The system contains 20 chromatographic columns and uses D001 ammonium type strong acid cation exchange resin for separation. The separation temperature is 30℃, the feed flow rate is 16mL / min, and 2% ammonia water is used for elution. The eluent flow rate is 36mL / min, and the resin column rotation time is 5min / column.

[0058] (5) Collect the first eluent (fast component A), which mainly contains pyroglutamic acid and ammonium sulfate; evaporate the water and then dry to obtain the crude product. Dissolve the crude product in anhydrous ethanol. Ammonium sulfate is insoluble in anhydrous ethanol. Filter and dry to obtain ammonium sulfate. The purity of ammonium sulfate reaches 95% and the yield is 96%. The clear liquid is concentrated by distillation. The vacuum degree is controlled at -0.085 MPa and the distillation temperature is 60℃. The liquid is concentrated to 1 / 8 of the initial volume. The liquid is cooled to 10℃ to crystallize. Centrifuge and dry to obtain pure pyroglutamic acid. The purity of pyroglutamic acid reaches 96% and the yield reaches 94.5%.

[0059] (6) Collect the second eluent (slow component B), in which the purity of glutamic acid is 92% and the yield is 96%, and reuse it in the isoelectric crystallizer.

[0060] Example 3

[0061] This embodiment provides a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid, comprising the following steps:

[0062] (1) Take 100L of isoelectric stock solution of glutamic acid, in which the concentration of glutamic acid is 40g / L, the concentration of pyroglutamic acid is 15g / L, and the concentration of ammonium sulfate is 130g / L. Use ceramic membrane filtration for sterilization. The membrane pore size is 200nm, the inlet pressure is 0.22MPa, the temperature is 50℃, and the circulation flow rate is 4m³ / h. 3 / h, outlet pressure 0.15Mpa, when the retentate volume drops to one-fifth of the initial volume, water is added for dialysis, the glutamate concentration in the dialysate is detected, and dialysis is stopped when the glutamate concentration is less than 2g / L;

[0063] (2) The dialysate was pumped into a falling film evaporator for continuous concentration at a concentration temperature of 80°C and a vacuum of -0.08 MPa until it reached 45 Baume. Then it was transferred to a crystallizer for cooling and crystallization at a control cooling rate of 5°C / h until it reached 25°C for crystal growth for 5 hours. After that, ammonium sulfate and secondary mother liquor were obtained by centrifugation. The purity of ammonium sulfate was 84% ​​and the yield was 63%.

[0064] (3) Add 2% MSG-specific charcoal to the secondary mother liquor, decolorize at 55℃ for 40 min, and then filter through a plate and frame filter to obtain the decolorized liquor;

[0065] (4) The decolorizing solution was adjusted to pH 1.1 with sulfuric acid and then entered a simulated moving bed continuous chromatography system. The system contains 20 chromatographic columns and is separated using JK008 ammonium type strong acid cation exchange resin. The separation temperature is 30℃, the feed flow rate is 12mL / min, and 3% ammonia water is used for elution. The eluent flow rate is 35mL / min, and the resin column rotation time is 7min / column.

[0066] (5) Collect the first eluent (fast component A), which mainly contains pyroglutamic acid and ammonium sulfate; evaporate the water and then dry to obtain the crude product. Dissolve the crude product in anhydrous ethanol. Ammonium sulfate is insoluble in anhydrous ethanol. Filter and dry to obtain ammonium sulfate. The purity of ammonium sulfate reaches 96% and the yield is 92%. The clear liquid is concentrated by distillation. The vacuum degree is controlled at -0.09 MPa and the distillation temperature is 55°C. The liquid is concentrated to 1 / 6 of the initial volume. The liquid is cooled to 12°C to crystallize. Centrifuge and dry to obtain pure pyroglutamic acid. The purity of pyroglutamic acid reaches 98% and the yield reaches 90%.

[0067] (6) Collect the second eluent (slow component B), in which the purity of glutamic acid is 90% and the yield is 98%, and reuse it in the isoelectric crystallizer.

[0068] Example 4

[0069] This embodiment provides a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid, comprising the following steps:

[0070] (1) Take 100L of isoelectric stock solution of glutamic acid, in which the concentration of glutamic acid is 30g / L, the concentration of pyroglutamic acid is 8g / L, and the concentration of ammonium sulfate is 150g / L. Use ceramic membrane filtration for sterilization. The membrane pore size is 50nm, the inlet pressure is 0.25MPa, the temperature is 55℃, and the circulation flow rate is 4m³ / h. 3 / h, outlet pressure 0.13Mpa, when the retentate volume drops to one-fifth of the initial volume, water is added for dialysis, the glutamate concentration in the dialysate is detected, and dialysis is stopped when the glutamate concentration is less than 2g / L;

[0071] (2) The dialysate was pumped into a falling film evaporator for continuous concentration at a concentration temperature of 70°C and a vacuum of -0.08 MPa until it reached 45 Baume. Then it was transferred to a crystallizer for cooling and crystallization at a controlled cooling rate of 3°C / h until it reached 25°C for crystal growth for 4 hours. After that, ammonium sulfate and secondary mother liquor were obtained by centrifugation. The purity of ammonium sulfate was 86.5% and the yield was 62%.

[0072] (3) Add 3% MSG-specific charcoal to the secondary mother liquor, decolorize at 55℃ for 50 min, and then filter through a plate and frame filter to obtain the decolorized liquor;

[0073] (4) The decolorizing solution was adjusted to pH 1.0 with sulfuric acid and then entered a simulated moving bed continuous chromatography system. The system contains 20 chromatographic columns and is separated using WA-2 ammonium type strong acid cation exchange resin. The separation temperature is 25℃, the feed flow rate is 14mL / min, and 3% ammonia water is used for elution. The eluent flow rate is 30mL / min, and the resin column rotation time is 6min / column.

[0074] (5) Collect the first eluent (fast component A), which mainly contains pyroglutamic acid and ammonium sulfate; evaporate the water and then dry to obtain the crude product. Dissolve the crude product in anhydrous ethanol. Ammonium sulfate is insoluble in anhydrous ethanol. Filter and dry to obtain ammonium sulfate. The purity of ammonium sulfate reaches 94% and the yield is 94%. The clear liquid is concentrated by distillation. The vacuum degree is controlled at -0.08 MPa and the distillation temperature is 65℃. The liquid is concentrated to 1 / 7 of the initial volume. The liquid is cooled to 12℃ to crystallize. Centrifuge and dry to obtain pure pyroglutamic acid. The purity of pyroglutamic acid reaches 97% and the yield reaches 92%.

[0075] (6) Collect the second eluent (slow component B), in which the purity of glutamic acid is 95% and the yield is 95%, and reuse it in the isoelectric crystallizer.

[0076] Example 5

[0077] This embodiment provides a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid, comprising the following steps:

[0078] (1) Take 100L of isoelectric stock solution of glutamic acid, in which the concentration of glutamic acid is 20g / L, the concentration of pyroglutamic acid is 20g / L, and the concentration of ammonium sulfate is 120g / L. Use ceramic membrane filtration for sterilization. The membrane pore size is 200nm, the inlet pressure is 0.25MPa, the temperature is 60℃, and the circulation flow rate is 3m³ / h. 3 / h, outlet pressure 0.15Mpa, when the retentate volume drops to one-fifth of the initial volume, water is added for dialysis, the glutamate concentration in the dialysate is detected, and dialysis is stopped when the glutamate concentration is less than 2g / L;

[0079] (2) The dialysate was pumped into a falling film evaporator for continuous concentration at a concentration temperature of 80°C and a vacuum of -0.09 MPa. It was concentrated to 50 Baume', and then transferred to a crystallizer for cooling and crystallization. The cooling rate was controlled at 3°C / h. The crystals were grown at 20°C for 5h. After that, ammonium sulfate and secondary mother liquor were obtained by centrifugation. The purity of ammonium sulfate was 85% and the yield was 64%.

[0080] (3) Add 2% MSG-specific charcoal to the secondary mother liquor, decolorize at 50℃ for 50 min, and then filter through a plate and frame filter to obtain the decolorized liquor;

[0081] (4) The decolorizing solution was adjusted to pH 1.0 with sulfuric acid and then entered a simulated moving bed continuous chromatography system. The system contains 20 chromatographic columns and uses D61 ammonium type strong acid cation exchange resin for separation. The separation temperature is 30℃, the feed flow rate is 10mL / min, and 2% ammonia water is used for elution. The eluent flow rate is 25mL / min, and the resin column rotation time is 5min / column.

[0082] (5) Collect the first eluent (fast component A), which mainly contains pyroglutamic acid and ammonium sulfate; evaporate the water and then dry to obtain the crude product. Dissolve the crude product in anhydrous ethanol. Ammonium sulfate is insoluble in anhydrous ethanol. Filter and dry to obtain ammonium sulfate. The purity of ammonium sulfate reaches 94.5% and the yield is 93.5%. The clear liquid is concentrated by distillation, and the vacuum degree is controlled at -0.085 MPa. The distillation temperature is 65℃. The liquid is concentrated to 1 / 7 of the initial volume, cooled to 15℃ to crystallize, centrifuged and dried to obtain pure pyroglutamic acid. The purity of pyroglutamic acid reaches 98.5% and the yield reaches 93%.

[0083] (6) Collect the second eluent (slow component B), in which the purity of glutamic acid is 94.5% and the yield is 94.6%, and reuse it in the isoelectric crystallizer.

[0084] Comparative Example 1

[0085] This comparative example provides a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid, comprising the following steps:

[0086] (1) Take 100L of isoelectric stock solution of glutamic acid, in which the concentration of glutamic acid is 20g / L, the concentration of pyroglutamic acid is 20g / L, and the concentration of ammonium sulfate is 120g / L. Use ceramic membrane filtration for sterilization. The membrane pore size is 200nm, the inlet pressure is 0.25MPa, the temperature is 60℃, and the circulation flow rate is 3m³ / h. 3 / h, outlet pressure 0.15Mpa, when the retentate volume drops to one-fifth of the initial volume, water is added for dialysis, the glutamate concentration in the dialysate is detected, and dialysis is stopped when the glutamate concentration is less than 2g / L;

[0087] (2) Add 2% MSG-specific charcoal to the dialysis solution, decolorize at 50°C for 50 min, and then filter through a plate and frame filter to obtain the decolorized solution;

[0088] (3) The decolorizing solution was adjusted to pH 1.0 with sulfuric acid and then entered a simulated moving bed continuous chromatography system. The system contains 20 chromatographic columns and uses D61 ammonium type strong acid cation exchange resin for separation. The separation temperature is 30℃, the feed flow rate is 10mL / min, and 2% ammonia water is used for elution. The eluent flow rate is 25mL / min, and the resin column rotation time is 5min / column.

[0089] (4) Collect the first eluent (fast component A), which mainly contains pyroglutamic acid and ammonium sulfate; pump the eluent into a falling film evaporator for pre-concentration, then continue to evaporate the water, dry to obtain crude product, add anhydrous ethanol to dissolve the crude product, ammonium sulfate is insoluble in anhydrous ethanol, filter and dry to obtain ammonium sulfate, the purity of ammonium sulfate reaches 82%, and the yield is 83%; the clear liquid is concentrated by distillation, cooled and crystallized under vacuum of -0.085 MPa, distillation temperature of 65℃, concentrated to 1 / 7 of the initial volume, cooled to 15℃ for crystallization, centrifuged and dried to obtain pure pyroglutamic acid, the purity of pyroglutamic acid reaches 90%, and the yield reaches 88%;

[0090] (5) Collect the second eluent (slow component B), in which the purity of glutamic acid is 85% and the yield is 90%.

[0091] Comparative Example 2

[0092] This comparative example provides a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid, comprising the following steps:

[0093] (1) Take 100L of isoelectric stock solution of glutamic acid, in which the concentration of glutamic acid is 20g / L, the concentration of pyroglutamic acid is 20g / L, and the concentration of ammonium sulfate is 120g / L. Use ceramic membrane filtration for sterilization. The membrane pore size is 200nm, the inlet pressure is 0.25MPa, the temperature is 60℃, and the circulation flow rate is 3m³ / h. 3 / h, outlet pressure 0.15Mpa, when the retentate volume drops to one-fifth of the initial volume, water is added for dialysis, the glutamate concentration in the dialysate is detected, and dialysis is stopped when the glutamate concentration is less than 2g / L;

[0094] (2) The dialysate was pumped into a falling film evaporator for continuous concentration at a concentration temperature of 80°C and a vacuum of -0.09 MPa. It was concentrated to 50 Baume', and then transferred to a crystallizer for cooling and crystallization. The cooling rate was controlled at 3°C / h. The crystals were grown at 20°C for 5h. After that, ammonium sulfate and secondary mother liquor were obtained by centrifugation. The purity of ammonium sulfate was 85% and the yield was 64%.

[0095] (3) Add 2% MSG-specific charcoal to the secondary mother liquor, decolorize at 50℃ for 50 min, and then filter through a plate and frame filter to obtain the decolorized liquor;

[0096] (4) The decolorizing solution was adjusted to pH 1.0 with sulfuric acid and then entered a simulated moving bed continuous chromatography system. The system contains 20 chromatographic columns and uses D61 ammonium type strong acid cation exchange resin for separation. The separation temperature is 30℃, the feed flow rate is 10mL / min, and 2% ammonium sulfate solution is used for elution. The eluent flow rate is 25mL / min, and the resin column rotation time is 5min / column.

[0097] (5) Collect the first eluent (fast component A), which mainly contains pyroglutamic acid and ammonium sulfate; evaporate the water and then dry to obtain the crude product. Dissolve the crude product in anhydrous ethanol. Sodium sulfate and ammonium sulfate are insoluble in anhydrous ethanol. Filter and dry to obtain a mixture of sodium sulfate and ammonium sulfate. The purity of ammonium sulfate reaches 92% and the yield is 94%. The clear liquid is concentrated by distillation, and the vacuum degree is controlled at -0.085 MPa. The distillation temperature is 65℃, and the liquid is concentrated to 1 / 7 of the initial volume. The liquid is cooled to 15℃ to crystallize. Centrifuge and dry to obtain pure pyroglutamic acid. The purity of pyroglutamic acid reaches 94% and the yield reaches 91%.

[0098] (6) Collect the second eluent (slow component B), in which the purity of glutamic acid is 87% and the yield is 83%, and reuse it in the isoelectric crystallizer.

[0099] Comparative Example 3

[0100] This comparative example provides a method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid, comprising the following steps:

[0101] (1) Take 100L of isoelectric stock solution of glutamic acid, in which the concentration of glutamic acid is 20g / L, the concentration of pyroglutamic acid is 20g / L, and the concentration of ammonium sulfate is 120g / L. Use ceramic membrane filtration for sterilization. The membrane pore size is 200nm, the inlet pressure is 0.25MPa, the temperature is 60℃, and the circulation flow rate is 3m³ / h. 3 / h, outlet pressure 0.15Mpa, when the retentate volume drops to one-fifth of the initial volume, water is added for dialysis, the glutamate concentration in the dialysate is detected, and dialysis is stopped when the glutamate concentration is less than 2g / L;

[0102] (2) The dialysate was pumped into a falling film evaporator for continuous concentration at a concentration temperature of 80°C and a vacuum of -0.09 MPa. It was concentrated to 50 Baume', and then transferred to a crystallizer for cooling and crystallization. The cooling rate was controlled at 3°C / h. The crystals were grown at 20°C for 5h. After that, ammonium sulfate and secondary mother liquor were obtained by centrifugation. The purity of ammonium sulfate was 85% and the yield was 64%.

[0103] (3) Add 2% MSG-specific charcoal to the secondary mother liquor, decolorize at 50℃ for 50 min, and then filter through a plate and frame filter to obtain the decolorized liquor;

[0104] (4) The decolorizing solution was adjusted to pH 1.0 with sulfuric acid and then entered a simulated moving bed continuous chromatography system. The system contains 20 chromatographic columns and uses D61 ammonium type strong acid cation exchange resin for separation. The separation temperature is 30℃, the feed flow rate is 10mL / min, and 2% ammonia water is used for elution. The eluent flow rate is 25mL / min, and the resin column rotation time is 5min / column.

[0105] (5) Collect the first eluent (fast component A), which mainly contains pyroglutamic acid and ammonium sulfate; evaporate the water and then dry to obtain the crude product. Dissolve the crude product in methanol. Ammonium sulfate is insoluble in methanol. Filter and dry to obtain ammonium sulfate. The purity of ammonium sulfate reaches 92% and the yield is 90%. The clear liquid is concentrated by distillation, and the vacuum degree is controlled at -0.085 MPa. The distillation temperature is 60℃. The liquid is concentrated to 1 / 7 of the initial volume, cooled to 15℃ to crystallize, centrifuged and dried to obtain pure pyroglutamic acid. The purity of pyroglutamic acid reaches 96.5% and the yield reaches 90%.

[0106] (6) Collect the second eluent (slow component B), in which the purity of glutamic acid is 94% and the yield is 95%, and reuse it in the isoelectric crystallizer.

[0107] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for recovering glutamic acid, ammonium sulfate, and pyroglutamic acid from an isoelectric mother liquor of glutamic acid, characterized in that, The method includes: isoelectric mother liquor containing no bacteria is crystallizing to obtain ammonium sulfate and a secondary mother liquor; chromatographically separating the secondary mother liquor to obtain a first eluent containing pyroglutamic acid and ammonium sulfate and a second eluent containing glutamic acid; evaporating and drying the first eluent to obtain a crude mixture of pyroglutamic acid and ammonium sulfate; mixing the crude product with ethanol and separating to obtain ammonium sulfate and a clear liquid; concentrating and crystallizing the clear liquid to obtain pyroglutamic acid; and separating glutamic acid from the second eluent. The chromatographic separation uses an ammonium-type strong acid cation exchange resin with 2-4% ammonia water as the eluent.

2. The method according to claim 1, characterized in that, The chromatographic separation temperature is 25–30°C.

3. The method according to claim 1, characterized in that, The chromatographic separation uses a simulated moving bed continuous chromatography system with a feed flow rate of 10–16 mL / min, an eluent flow rate of 22–36 mL / min, and a resin column rotation time of 5–7 min / column.

4. The method according to any one of claims 1 to 3, characterized in that, The secondary mother liquor is first decolorized to obtain a decolorized solution. The pH of the decolorized solution is then adjusted to 0.8-1.2 before chromatographic separation.

5. The method according to claim 4, characterized in that, The secondary mother liquor was decolorized using activated carbon, and the resulting decolorized solution was obtained by filtration.

6. The method according to any one of claims 1 to 3, 5, characterized in that, The crystallization method for ammonium sulfate is concentration crystallization. The conditions for concentration crystallization are as follows: the isoelectric mother liquor containing no bacteria is continuously concentrated to 45-50 Baumé under the conditions of 70-80℃ and vacuum degree of -0.08 to -0.09 MPa, followed by cooling crystallization at a cooling rate of 3-5℃ / h, a crystallization temperature of 20-25℃, and a crystallization time of 4-6h.

7. The method according to any one of claims 1 to 3 and 5, characterized in that, The concentration of glutamic acid in the bacterial-free glutamic acid isoelectric mother liquor is ≥10 g / L, the concentration of pyroglutamic acid is ≥5 g / L, and the concentration of ammonium sulfate is ≥20 g / L.

8. The method according to claim 7, characterized in that, The method for preparing the cell-free glutamic acid isoelectric mother liquor includes: removing the cells from the cell-containing isoelectric mother liquor by filtration through a ceramic membrane, wherein the ceramic membrane has a pore size of 50-200 nm, an inlet pressure of 0.2-0.3 MPa, a temperature of 50-60 °C, and a circulation flow rate of 2-5 m³ / h. 3 / h, with an outlet pressure of 0.10~0.15Mpa.

9. The application of the method according to any one of claims 1 to 8 in the resource utilization treatment of glutamic acid production waste liquid.

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