Process for the recovery of pyroglutamic acid from glutamic acid fermentation broth

Abstract

The application provides a method for recovering pyroglutamic acid from glutamic acid fermentation liquor, which comprises the following steps: removing bacteria bodies from the glutamic acid fermentation liquor through centrifugation; extracting glutamic acid from the supernatant through isoelectric separation after concentration; separating ammonium sulfate from the glutamic acid isoelectric mother liquor through concentration and crystallization; separating through electrodialysis after decolorization and filtration of the secondary mother liquor; collecting concentrated water and dilute water respectively; recycling the dilute water to the isoelectric separation process; and separating ammonium sulfate and pyroglutamic acid through alcohol extraction and filtration of the concentrated water. The method can reduce production cost and provide a new means for effective recovery and utilization of pyroglutamic acid in the monosodium glutamate industry by treating the glutamic acid isoelectric mother liquor through electrodialysis to recover high-value-added product pyroglutamic acid.

Description

Technical Field

[0001] This invention relates to the field of biochemical engineering, and more specifically, to a method for recovering pyroglutamic acid from glutamic acid fermentation broth. Background Technology

[0002] Pyroglutamic acid, also known as 5-carboxypyrrolidone, oxidized proline, and 2-pyrrolidone-5-carboxylic acid (PCA), has the molecular formula C5H7NO3 and a molecular weight of 129.11. It is a white crystalline powder, readily soluble in water, ethanol, acetone, and glacial acetic acid, slightly soluble in ethyl acetate, and insoluble in ether. Its solubility in water at 25°C is over 40g / 100g. Its molecular structure is as follows:

[0003]

[0004] Pyroglutamic acid is a cyclic amino acid that can be generated as an intermediate product during amino acid metabolism and transport via enzymatic reactions. It is also a component of many important peptides and proteins in the biosynthesis of proteins. Pyroglutamic acid is widely found in the plant and animal kingdoms; it has been detected in everything from human retinal nerve cells, tissues, and body fluids to vegetables, fruits, coffee beans, cheese, and beer. PCA is an amino acid whose sodium salt can enhance skin's softness and elasticity, giving it a radiant glow. Added to cosmetics, it not only imparts excellent moisturizing and whitening effects but is also very safe. It can also be used in pure cotton textiles to improve their moisturizing, antibacterial, and finishing properties, thus finding wide application in the daily chemical and pharmaceutical industries.

[0005] The synthesis mechanism of pyroglutamic acid: Glutamic acid undergoes dehydration and cyclization under prolonged heating to form pyroglutamic acid. Pyroglutamic acid then hydrolyzes under acidic or alkaline conditions to regenerate glutamic acid. The reaction equation is as follows:

[0006]

[0007] Electrodialysis is an emerging membrane separation technology. Due to its high efficiency, low energy consumption, high selectivity for separated components, low pretreatment requirements, high raw water recovery rate, and environmental friendliness, it has been widely used in various industries both domestically and internationally. The principle of electrodialysis involves alternating anion and cation exchange membranes between positive and negative electrodes, separated by a special partition, forming two systems: desalination (desalination) and concentration. Under the influence of a direct current electric field, driven by the potential difference, and utilizing the selective permeability of the ion exchange membranes, a portion of the water is desalinated, and another portion is concentrated, separating electrolytes from the solution, thereby achieving concentration, desalination, purification, and refinement of the solution. Compared to other membrane separation technologies, electrodialysis requires only minimal pretreatment and is unaffected by pressure to obtain high-quality water. Another advantage is that it does not require energy conversion; electrical energy can be directly utilized, even when the energy input changes directly.

[0008] Amino acids contain both acidic functional groups (COOH) and basic functional groups (NH2) in their molecules, making them amphoteric electrolytes. When the pH of an amino acid solution is at its isoelectric point, the amino acid exists primarily as a neutral molecule, with an equal amount of positive and negative ions. In this case, the amino acid solution is electrically neutral and does not move in a direct current electric field. When the pH of the amino acid solution is higher than its isoelectric point, the amino acid exists as a basic negative ion and can move towards the anode through the anion exchange membrane (A) in a direct current electric field. Conversely, when the pH of the solution is lower than its isoelectric point, the amino acid exists as an acidic positive ion and can move towards the cathode through the cation exchange membrane (C) in a direct current electric field. Due to these characteristics, amino acids can be prepared, separated, and purified using electrodialysis.

[0009] Isoelectric mother liquor of glutamic acid is the waste liquid generated after isoelectric crystallization and centrifugal separation during the extraction of glutamic acid. Its main components are glutamic acid, ammonium sulfate, pyroglutamic acid, microbial protein, and pigments. The composition of the isoelectric mother liquor varies slightly depending on the glutamic acid extraction process. 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 concentrate and spray-dry the mother liquor to prepare bio-organic fertilizer.

[0010] Typically, pyroglutamic acid in glutamic acid fermentation broth is very low, approximately 3% of the total glutamic acid content. However, the amount of pyroglutamic acid gradually increases as the extraction process progresses. During the glutamic acid concentration stage, water shortage and prolonged heating cause glutamic acid to dehydrate and cyclize, forming pyroglutamic acid. In the isoelectric stage, the addition of a large amount of acid releases a significant amount of heat, further increasing the amount of pyroglutamic acid. On the one hand, the production of pyroglutamic acid reduces the extraction yield; on the other hand, the final spray drying of glutamic acid and pyroglutamic acid with the mother liquor to prepare bio-organic fertilizer results in resource waste and increases production costs.

[0011] The main problems in the glutamic acid isoelectric mother liquor treatment process in the current monosodium glutamate production are: (1) the fermentation broth before glutamic acid concentration isoelectric is not subjected to sterilization pretreatment, resulting in high glutamic acid concentration temperature, and uneven heating will increase the production of pyroglutamic acid, and the existence of the bacteria in the fermentation broth will also affect the glutamic acid isoelectric crystallization and separation, and reduce the glutamic acid extraction yield; (2) the current method for treating glutamic acid isoelectric mother liquor by electrodialysis mainly focuses on recovering the acid, base, glutamic acid and ammonium sulfate in the isoelectric mother liquor, and the high value-added product pyroglutamic acid is not recovered and utilized. SUMMARY

[0012] The purpose of the present application is to provide a method for recovering pyroglutamic acid from glutamic acid fermentation broth.

[0013] In order to achieve the purpose of the present application, the present application provides a method for recovering pyroglutamic acid from glutamic acid fermentation broth, comprising the following steps:

[0014] (1) removing the bacteria from the glutamic acid fermentation broth by centrifugation;

[0015] (2) concentrating the supernatant obtained in step (1) and then performing isoelectric separation to extract glutamic acid;

[0016] (3) concentrating and crystallizing the glutamic acid isoelectric mother liquor obtained in step (2) to separate ammonium sulfate;

[0017] (4) performing electrodialysis separation on the secondary mother liquor obtained in step (3) after decolorization and filtration, and collecting the concentrated water and the dilute water; wherein the dilute water contains glutamic acid, and the concentrated water contains pyroglutamic acid and ammonium sulfate; and recycling to the isoelectric crystallization tank;

[0018] (5) recycling the dilute water to the isoelectric separation process; drying the concentrated water after evaporation to remove water to obtain a crude product, dissolving the crude product in anhydrous ethanol, filtering out the ammonium sulfate which is insoluble in anhydrous ethanol, and concentrating the clear liquid to obtain a pure pyroglutamic acid product.

[0019] Further, the glutamic acid content in the glutamic acid fermentation broth in step (1) is 180-200 g / L, the pyroglutamic acid content is 4-6 g / L, and the transmittance of the fermentation broth is 5-7%; the bacteria are removed by centrifugation (using a disc separator to remove the bacteria), and the transmittance of the obtained supernatant is > 70%.

[0020] Further, the supernatant in step (2) is concentrated at 70-75℃ and a vacuum degree of -0.08 to -0.09 MPa, and the glutamic acid content in the obtained concentrated liquid is 330-350 g / L, and the pyroglutamic acid content is 8-10 g / L.

[0021] Further, the supernatant of step (2) is concentrated, and the concentrated solution is moved to a crystallization tank, the pH is adjusted to 3.2-3.3 by sulfuric acid, and then isoelectric separation (crystal growth) is performed at 12-15℃ for 5-6h, and then wet glutamic acid and glutamic acid isoelectric mother liquor is separated.

[0022] Further, the isoelectric mother liquor of glutamic acid separated in step (3) is pumped into an evaporator for concentration, the feed is 20-21 Be', the concentration temperature is 80-85℃, and the concentration is performed to 1 / 3-1 / 4 of the volume of the isoelectric mother liquor of glutamic acid, then the temperature is lowered to 30-50℃, and the crystal growth is performed for 2-3h, and then ammonium sulfate crystals and secondary mother liquor are separated.

[0023] Further, the content of glutamic acid in the secondary mother liquor of step (4) is 70-80g / L, the content of pyroglutamic acid is 37-45g / L, and the content of ammonium sulfate is 60-85g / L.

[0024] Further, 1-2% activated carbon is added to the secondary mother liquor in step (4), and the decolorization is performed at 40-50℃ for 40-60min, and then the decolorized solution is obtained by plate and frame filtration.

[0025] Further, the decolorized solution is adjusted to pH 3.2-3.3 by sulfuric acid, and then enters a three-chamber single-pole membrane electrodialysis system, the current density is controlled to 15-30mA / cm 2 , and the feed flow is 5-8L / h, and then the electrodialysis separation is performed.

[0026] Preferably, the C-A type three-chamber single-pole membrane electrodialysis system comprises 1 pair of electrodes and 5 pairs of homogeneous ion exchange membranes, wherein the anion exchange membrane is a polyethylene grafted polystyrene quaternary ammonium type strong alkaline anion exchange membrane, the cation exchange membrane is a polyethylene grafted polystyrene sulfonic acid type strong acid cation exchange membrane, and the effective membrane area is 300cm 2 . The system is purchased from Beijing Jingrun Environmental Protection Technology Co., Ltd., and the equipment model is JRED-M1.

[0027] The principle diagram of the C-A type three-chamber single-pole membrane electrodialysis system is shown in Figure 1 .

[0028] The process flow diagram of the method for recovering pyroglutamic acid from glutamic acid fermentation broth is shown in Figure 2 .

[0029] In the present application, the glutamic acid fermentation broth is a microbial culture obtained by culturing corynebacterium glutamicum or brevibacterium flavum as a fermentation strain.

[0030] The fermentation process can be referred to patent CN103243131B and CN106701855A, etc.

[0031] By the above technical scheme, the present application has at least the following advantages and beneficial effects:

[0032] (I) Before the glutamic acid fermentation liquid is concentrated, the bacteria bodies are removed by using a disc separator, the concentration temperature is reduced to reduce the pyroglutamic acid production, and the yield of glutamic acid isocratic crystallization extraction is high.

[0033] (II) The high-value product pyroglutamic acid in the glutamic acid isocratic mother liquor is recovered by using electrodialysis, and the production cost can be reduced.

[0034] (III) Before the isocratic mother liquor is treated by electrodialysis, most of ammonium sulfate is extracted by concentration and salting-out, the load of subsequent electrodialysis treatment is reduced, and equipment investment is saved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a C-A type three-chamber single electrode membrane electrodialysis system principle diagram of the application.

[0036] Figure 2 It is a process flow chart of the method for recovering pyroglutamic acid from glutamic acid fermentation liquid. DETAILED DESCRIPTION

[0037] The application provides a method for recovering pyroglutamic acid from glutamic acid isocratic mother liquor, comprising the following steps:

[0038] 1) The fermentation liquid is first removed of bacteria bodies by using a disc separator;

[0039] 2) After the supernatant is concentrated, glutamic acid is extracted by isoelectric separation;

[0040] 3) The isocratic mother liquor is further concentrated and crystallized to separate ammonium sulfate;

[0041] 4) The secondary mother liquor is decolorized, filtered and separated by electrodialysis;

[0042] 5) The fresh water is reused in the isoelectric separation process, the concentrated water is filtered by alcohol extraction, and ammonium sulfate and pyroglutamic acid are separated and obtained.

[0043] Further, in step 1), the content of glutamic acid in the fermentation liquid is 180-200 g / L, the content of pyroglutamic acid is 4-6 g / L, and the light transmittance of the fermentation liquid is 5-7%.

[0044] Further, in step 2), the concentration temperature is 70-75℃, the concentration of glutamic acid in the concentrated liquid reaches 330-350 g / L, and the concentration of pyroglutamic acid is 8-10 g / L.

[0045] Further, in step 2), the isoelectric pH is 3.2-3.3, the cooling temperature is 12-15℃, and the crystal growth time is 5-6 h.

[0046] Further, in step 3), the isocratic mother liquor is 20-21 Be', the concentration temperature is 80-85℃, the concentration multiple is 3-4 times, the crystallization temperature is 30-50℃, and the crystal growth time is 2-3 h.

[0047] Further, the glutamic acid content of the secondary mother liquor in step 4) is 70-80 g / L, the pyroglutamic acid content is 37-45 g / L, and the ammonium sulfate content is 60-85 g / L.

[0048] Further, the decolorization conditions in step 4) are a temperature of 40-50°C, an activated carbon addition amount of 1-2%, and a decolorization time of 40-60 min.

[0049] Further, the electrodialysis system in step 4) is a C-A type three-chamber single-pole homogeneous membrane system, the current density is 15-30 mA / cm 2 , and the feed flow rate is 5-8 L / h.

[0050] Further, the alcohol used in step 5) is anhydrous ethanol.

[0051] The following examples are used to illustrate the present application, but are not intended to limit the scope of the present application. If not specifically indicated, the technical means used in the examples are conventional means known to those skilled in the art, and the raw materials used are commercially available.

[0052] The experimental methods involved in the following examples are as follows:

[0053] Glutamic acid content determination method: determined by using a biosensor SBA-40C.

[0054] Pyroglutamic acid content determination method: determined by using a high-performance liquid chromatography method according to GB / T 35799-2018.

[0055] Ammonium sulfate determination method: determined by using a nitrogen determination instrument method to determine the free ammonium nitrogen content and then converted for determination.

[0056] Transmittance determination method: determined by using a spectrophotometer method.

[0057] The C-A type three-chamber single-pole membrane electrodialysis system comprises one pair of electrodes and five pairs of homogeneous ion exchange membranes, wherein the anion exchange membrane is a polyethylene grafted polystyrene quaternary ammonium type strong alkaline anion exchange membrane, the cation exchange membrane is a polyethylene grafted polystyrene sulfonic acid type strong acid cation exchange membrane, and the effective membrane area is 300 cm 2 . It is purchased from Beijing Jingrun Environmental Protection Technology Co., Ltd. and the equipment model is JRED-M1.

[0058] The specific method for obtaining the glutamic acid fermentation broth in the following examples can be found in patent CN103243131B (specification examples 7 and 11), and the fermentation strain is Corynebacterium glutamicum or Brevibacterium flavum.

[0059] Example 1: Method for recovering pyroglutamic acid from glutamic acid fermentation broth

[0060] (1) Take glutamic acid fermentation broth 300L (CN103243131B specification example 7) using disc separator for centrifugal separation, feed fermentation broth light transmittance 5%, glutamic acid content 200g / L, pyroglutamic acid content 6g / L, feed flow 300L / h, speed 8000rpm, control the discharge flow, 430nm detection outlet centrifugal clear liquid light transmittance, light transmittance reaches more than 70% to start collecting clear liquid, the residue is dried and crushed to prepare the bacterial protein.

[0061] (2) Centrifugal clear liquid 280L is pumped into falling film evaporator for continuous concentration, concentration temperature 70℃, vacuum degree-0.09Mpa, concentrated to glutamic acid concentration reaches 345g / L, detect the pyroglutamic acid concentration in the concentrated liquid 10g / L.

[0062] (3) The concentrated liquid is transferred into the isoelectric crystallization tank, and concentrated sulfuric acid is added to adjust the pH to 3.2. The temperature is reduced to 15℃ by using refrigerated water. After 5h of crystal growth, wet glutamic acid and isoelectric mother liquor are obtained by centrifugal separation. The extraction yield of glutamic acid can reach 95%. The residual glutamic acid in the isoelectric mother liquor is 25g / L, the pyroglutamic acid is 12g / L, and the ammonium sulfate is 140g / L.

[0063] (4) The isoelectric mother liquor of glutamic acid obtained by separation is pumped into the evaporator for concentration. The feed is 21Be', the concentration temperature is 85℃, and the volume of the isoelectric mother liquor is concentrated to 1 / 3. Then the temperature is reduced to 50℃ for 2h of crystal growth, and ammonium sulfate crystals and secondary mother liquor are obtained by centrifugal separation. The glutamic acid content in the secondary mother liquor after separation of ammonium sulfate is 70g / L, the pyroglutamic acid content is 40g / L, and the ammonium sulfate content is 80g / L.

[0064] (5) 2% activated carbon is added to the secondary mother liquor, and decolorization is carried out at 50℃ for 40min. Then plate and frame filtration is used to obtain decolorized liquid.

[0065] (6) The decolorized liquid is adjusted to pH 3.2-3.3 by using sulfuric acid, and then enters the C-A type three-chamber single-pole membrane electrodialysis system. The effective membrane area is 300cm 2 , the current density is controlled at 30mA / cm 2 , the feed flow is 8L / h, and the concentrated water and dilute water are collected respectively.

[0066] (7) The dilute water mainly contains glutamic acid, which is recycled to the isoelectric crystallization tank.

[0067] (8) The concentrated water mainly contains pyroglutamic acid and ammonium sulfate. The concentrated water is evaporated to remove water, and then dried to obtain a crude product. The crude product is dissolved in anhydrous ethanol, and the ammonium sulfate is insoluble in anhydrous ethanol and is removed by filtration. The clear liquid is concentrated by distillation, cooled and crystallized, and dried to obtain pyroglutamic acid pure product. The pyroglutamic acid content reaches 98%, and the yield reaches 95%.

[0068] Method for recovering pyroglutamic acid from glutamic acid fermentation broth

[0069] (1) 300 L of glutamic acid fermentation broth (CN103243131B specification example 11) was centrifuged using a disc separator, the feed broth had a light transmittance of 7%, a glutamic acid content of 190 g / L, and a pyroglutamic acid content of 4 g / L, the feed flow rate was 300 L / h, the rotation speed was 8000 rpm, the discharge flow rate was controlled, the light transmittance of the outlet centrifugal clear liquid was detected at 430 nm, and when the light transmittance reached more than 70%, the clear liquid was collected, and the bacterial residue was dried and crushed to prepare bacterial protein.

[0070] (2) 280 L of the centrifugal clear liquid was pumped into a falling film evaporator for continuous concentration, the concentration temperature was 75°C, the vacuum degree was -0.08 Mpa, and the glutamic acid concentration was concentrated to 350 g / L, and the pyroglutamic acid concentration in the concentrated liquid was detected to be 10 g / L.

[0071] (3) The concentrated liquid was transferred into an isoelectric crystallization tank, concentrated sulfuric acid was added for pH adjustment to 3.3, chilled water was used for cooling to 12°C, and after crystal growth for 5 h, wet glutamic acid and isoelectric mother liquor were obtained by centrifugal separation, and the glutamic acid extraction yield could reach 96%; the residual glutamic acid in the isoelectric mother liquor was detected to be 20 g / L, the pyroglutamic acid was 11 g / L, and the ammonium sulfate was 100 g / L.

[0072] (4) The isoelectric mother liquor of glutamic acid obtained by separation was pumped into an evaporator for concentration, the feed Baume was 20.2 Be', the concentration temperature was 85°C, the isoelectric mother liquor of glutamic acid was concentrated to 1 / 4 of the volume, then cooled to 30°C for crystal growth for 3 h, and ammonium sulfate crystals and secondary mother liquor were obtained by centrifugal separation. The secondary mother liquor after separation of ammonium sulfate had a glutamic acid content of 73 g / L, a pyroglutamic acid content of 45 g / L, and an ammonium sulfate content of 60 g / L.

[0073] (5) 2% activated carbon was added to the secondary mother liquor, and decolorization was performed at 50°C for 40 min, and then plate and frame filtration was performed to obtain a decolorized liquid.

[0074] (6) The decolorized liquid was adjusted to pH 3.2-3.3 using sulfuric acid, and then entered a C-A type three-chamber single-pole membrane electrodialysis system, the effective membrane area was 300 cm 2 , the current density was controlled to be 20 mA / cm 2 , the feed flow rate was 5 L / h, and concentrated water and dilute water were collected respectively.

[0075] (7) The dilute water mainly contained glutamic acid, which was reused in the isoelectric crystallization tank.

[0076] (8) The concentrated water mainly contains pyroglutamic acid and ammonium sulfate; the concentrated water is evaporated to remove water, and then dried to obtain a crude product; the crude product is dissolved in anhydrous ethanol, and the ammonium sulfate is insoluble in the anhydrous ethanol and is removed by filtration; the filtrate is concentrated by distillation, and then crystallized by lowering the temperature and dried to obtain a pyroglutamic acid product, the content of pyroglutamic acid reaches 98.5%, and the yield reaches 96%.

[0077] Example 3: Method for recovering pyroglutamic acid from glutamic acid fermentation liquor

[0078] (1) 300 L of glutamic acid fermentation liquor (CN103243131B specification example 7) is centrifuged by a disc separator, the transmittance of the feed fermentation liquor is 6%, the content of glutamic acid is 195 g / L, the content of pyroglutamic acid is 5 g / L, the feed flow rate is 300 L / h, the rotation speed is 8000 rpm, the outlet flow rate is controlled, and the transmittance of the centrifugal clear liquid at the outlet is detected at 430 nm; when the transmittance reaches more than 70%, the clear liquid is collected; the bacterial residue is dried and crushed to prepare bacterial protein.

[0079] (2) 280 L of the centrifugal clear liquid is pumped into a falling film evaporator for continuous concentration; the concentration temperature is 70°C, the vacuum degree is -0.09 Mpa; the concentration is performed until the concentration of glutamic acid reaches 340 g / L, and the concentration of pyroglutamic acid in the concentrated liquid is detected to be 9 g / L.

[0080] (3) The concentrated liquid is transferred into an isoelectric crystallization tank, concentrated sulfuric acid is added for pH adjustment to 3.3, and chilled water is used for temperature reduction to 12°C; after crystal growth for 5 h, wet glutamic acid and isoelectric mother liquor are obtained by centrifugal separation; the extraction yield of glutamic acid can reach 95.3%; the residual glutamic acid in the isoelectric mother liquor is detected to be 22 g / L, the pyroglutamic acid is 10 g / L, and the ammonium sulfate is 120 g / L.

[0081] (4) The isoelectric mother liquor of glutamic acid obtained by separation is pumped into an evaporator for concentration; the feed Bé is 20.8 Be'; the concentration temperature is 80°C; the concentration is performed until the volume of the isoelectric mother liquor of glutamic acid is 1 / 4; then the temperature is lowered to 50°C for crystal growth for 3 h, and ammonium sulfate crystals and secondary mother liquor are obtained by centrifugal separation. The content of glutamic acid in the secondary mother liquor after separation of ammonium sulfate is 80 g / L, the content of pyroglutamic acid is 42 g / L, and the content of ammonium sulfate is 80 g / L.

[0082] (5) 2% activated carbon is added to the secondary mother liquor, and the temperature is lowered to 50°C for decolorization for 50 min; then plate and frame filtration is performed to obtain a decolorized liquid.

[0083] (6) The decolorized liquid is adjusted to pH 3.2-3.3 by adding sulfuric acid, and then enters a C-A type three-chamber single-pole membrane electrodialysis system; the effective membrane area is 300 cm 2 , the current density is controlled to be 15 mA / cm 2 , the feed flow rate is 8 L / h, and concentrated water and dilute water are collected respectively.

[0084] (7) The main component in fresh water is glutamic acid, which is reused to the isoelectric crystallization tank.

[0085] (8) The main components in concentrated water are pyroglutamic acid and ammonium sulfate; the concentrated water is evaporated to remove water, and then dried to obtain a crude product; the crude product is dissolved in anhydrous ethanol, and the ammonium sulfate is insoluble in anhydrous ethanol and removed by filtration; the clear solution is concentrated by distillation, and then cooled and crystallized to obtain pyroglutamic acid, the content of pyroglutamic acid reaches 97%, and the yield reaches 95.2%.

[0086] Example 4: Method for recovering pyroglutamic acid from glutamic acid fermentation liquor

[0087] (1) 300 L of glutamic acid fermentation liquor (CN103243131B specification example 11) is centrifuged by a disc separator; the transmittance of the feed fermentation liquor is 5.5%, the content of glutamic acid is 200 g / L, the content of pyroglutamic acid is 5.5 g / L, the feed flow rate is 300 L / h, the rotation speed is 8000 rpm, the discharge flow rate is controlled, and the transmittance of the outlet centrifugal clear liquid is detected at 430 nm; when the transmittance reaches more than 70%, the clear liquid is collected; the bacterial residue is dried and crushed to prepare bacterial protein.

[0088] (2) 280 L of the centrifugal clear liquid is pumped into a falling film evaporator for continuous concentration; the concentration temperature is 75°C, the vacuum degree is -0.085 Mpa; the concentration is performed until the concentration of glutamic acid reaches 350 g / L, and the concentration of pyroglutamic acid in the concentrated liquid is detected to be 10 g / L.

[0089] (3) The concentrated liquid is transferred into an isoelectric crystallization tank, concentrated sulfuric acid is added for pH adjustment to 3.2, and chilled water is used for cooling to 12°C; after crystal growth for 6 h, wet glutamic acid and isoelectric mother liquor are obtained by centrifugal separation; the extraction yield of glutamic acid can reach 95.5%; the residual glutamic acid in the isoelectric mother liquor is detected to be 20 g / L, the pyroglutamic acid is 10 g / L, and the ammonium sulfate is 130 g / L.

[0090] (4) The isoelectric mother liquor of glutamic acid obtained by separation is pumped into an evaporator for concentration; the feed Bome is 21 Be'; the concentration temperature is 85°C; the concentration is performed until the volume of the isoelectric mother liquor of glutamic acid is 1 / 3.5; then the temperature is lowered to 50°C for crystal growth for 3 h, and ammonium sulfate crystals and secondary mother liquor are obtained by centrifugal separation. The content of glutamic acid in the secondary mother liquor after separation of ammonium sulfate is 70 g / L, the content of pyroglutamic acid is 37 g / L, and the content of ammonium sulfate is 85 g / L.

[0091] (5) 2% activated carbon is added to the secondary mother liquor, and the temperature is lowered to 50°C for decolorization for 60 min; then plate and frame filtration is performed to obtain a decolorized liquid.

[0092] (6) The decolorized liquid is adjusted to pH 3.2-3.3 by sulfuric acid, and then enters a C-A type three-chamber single-pole membrane electrodialysis system; the effective membrane area is 300 cm 2 , and the current density is controlled to be 15 mA / cm 2, the feed flow rate was 5 L / h, and the concentrated water and the dilute water were collected respectively.

[0093] (7) The main component in the dilute water was glutamic acid, which was reused to the isoelectric crystallization tank.

[0094] (8) The concentrated water mainly contained pyroglutamic acid and ammonium sulfate; the concentrated water was evaporated to remove water, and then dried to obtain a crude product; the crude product was dissolved in anhydrous ethanol, and the ammonium sulfate was insoluble in the anhydrous ethanol and was removed by filtration; the clear liquid was concentrated by distillation, and then cooled and crystallized to obtain a pyroglutamic acid product; the content of pyroglutamic acid reached 97.5%, and the yield reached 94%.

[0095] Example 5: Method for recovering pyroglutamic acid from glutamic acid fermentation liquor

[0096] (1) 300 L of glutamic acid fermentation liquor (CN103243131B specification example 7) was centrifuged by using a disc separator; the feed liquor transmittance was 5.5%, the glutamic acid content was 200 g / L, the pyroglutamic acid content was 5.5 g / L, the feed flow rate was 300 L / h, the rotation speed was 8000 rpm, the outlet flow rate was controlled, and the outlet centrifugal clear liquid transmittance was detected at 430 nm; when the transmittance reached more than 70%, the clear liquid was collected; the bacterial residue was dried and crushed to prepare bacterial protein.

[0097] (2) 280 L of the centrifugal clear liquid was pumped into a falling film evaporator for continuous concentration; the concentration temperature was 75℃, the vacuum degree was -0.09 Mpa; when the glutamic acid concentration reached 350 g / L, the pyroglutamic acid concentration in the concentrated liquid was detected to be 10 g / L.

[0098] (3) The concentrated liquid was transferred into an isoelectric crystallization tank, concentrated sulfuric acid was added for pH adjustment to 3.2, and refrigerated water was used for cooling to 12℃; after crystal growth for 6 h, wet glutamic acid and isoelectric mother liquor were obtained by centrifugal separation; the glutamic acid extraction yield could reach 95.5%; the residual glutamic acid in the isoelectric mother liquor was detected to be 20 g / L, the pyroglutamic acid was 10 g / L, and the ammonium sulfate was 130 g / L.

[0099] (4) The isoelectric mother liquor of glutamic acid obtained by separation was pumped into an evaporator for concentration; the feed Bomei was 21 Be', the concentration temperature was 85℃; when the volume of the isoelectric mother liquor of glutamic acid was 1 / 3.5, the temperature was lowered to 50℃ for crystal growth for 3 h, and then ammonium sulfate crystals and secondary mother liquor were obtained by centrifugal separation. The glutamic acid content in the secondary mother liquor after separation of ammonium sulfate was 70 g / L, the pyroglutamic acid content was 37 g / L, and the ammonium sulfate content was 85 g / L.

[0100] (5) 2% of activated carbon was added to the secondary mother liquor, and the temperature was lowered to 50℃ for decolorization for 60 min; then, the decolorized liquid was obtained by plate and frame filtration.

[0101] (6) The decolorized liquid was adjusted to pH 3.2-3.3 by using sulfuric acid, and then entered a C-A type three-chamber single-pole membrane electrodialysis system; the effective membrane area was 300 cm2 , control current density 15 mA / cm 2 , feed flow rate 5 L / h, and concentrated water and dilute water were collected separately.

[0102] (7) The main component in the dilute water was glutamic acid, which was reused in the isoelectric crystallization tank.

[0103] (8) The concentrated water mainly contained pyroglutamic acid and ammonium sulfate; the concentrated water was evaporated to remove water, and then dried to obtain a crude product; the crude product was dissolved in anhydrous ethanol, and the ammonium sulfate was removed by filtration; the filtrate was concentrated by distillation, and then cooled and crystallized to obtain a pyroglutamic acid product; the pyroglutamic acid content reached 97.5%, and the yield reached 94%.

[0104] Comparative Example 1

[0105] (1) 300 L of glutamic acid fermentation broth (CN103243131B specification example 7) was taken; the transmittance of the fermentation broth was 5.5%, the glutamic acid content was 195 g / L, and the pyroglutamic acid content was 5 g / L.

[0106] (2) The fermentation broth was pumped into a falling film evaporator for continuous concentration; the concentration temperature was 85°C, the vacuum degree was -0.09 Mpa, the glutamic acid concentration was concentrated to 340 g / L, and the pyroglutamic acid concentration in the concentrated liquid was detected to be 17 g / L.

[0107] (3) The concentrated liquid was transferred into an isoelectric crystallization tank, concentrated sulfuric acid was added for pH adjustment to 3.2, and the temperature was lowered to 15°C using chilled water; after crystal growth for 5 h, wet glutamic acid and isoelectric mother liquor were obtained by centrifugal separation; the glutamic acid extraction yield could reach 90%; the residual glutamic acid in the isoelectric mother liquor was detected to be 30 g / L, the pyroglutamic acid was 18 g / L, and the ammonium sulfate was 120 g / L.

[0108] (4) The isoelectric mother liquor of glutamic acid obtained by separation was filtered by an ultrafiltration membrane to remove bacterial protein; the filtrate was pumped into an evaporator for concentration; the feed Brix was 20.5 Be', the concentration temperature was 85°C, and the concentration was 3 times; then the temperature was lowered to 30°C for crystal growth for 2-3 h, and ammonium sulfate crystals and secondary mother liquor were obtained by centrifugal separation. The glutamic acid content in the secondary mother liquor after separation of ammonium sulfate was 80 g / L, the pyroglutamic acid content was 55 g / L, and the ammonium sulfate content was 65 g / L.

[0109] (5) 2% activated carbon was added to the secondary mother liquor, and the temperature was lowered to 50°C for decolorization for 60 min; then plate and frame filtration was performed to obtain a decolorized liquid.

[0110] (6) The decolorized liquid was adjusted to pH 3.2-3.3 using sulfuric acid, and then entered a C-A type three-chamber monopolar membrane electrodialysis system; the effective membrane area was 300 cm 2 , control current density 20 mA / cm 2 , feed flow rate 5 L / h, and concentrated water and dilute water were collected separately.

[0111] (7) The main component of the fresh water is glutamic acid, which is reused to the isoelectric crystallization tank.

[0112] (8) The main components of the concentrated water are pyroglutamic acid and ammonium sulfate; the concentrated water is evaporated to remove water, and then dried to obtain a crude product; the crude product is dissolved in anhydrous ethanol, and the ammonium sulfate is removed by filtration because it is insoluble in anhydrous ethanol; the clear solution is concentrated by distillation, and then cooled and crystallized to obtain pyroglutamic acid; the content of pyroglutamic acid reaches 98%, and the yield reaches 95%.

[0113] Comparative Example 2

[0114] (1) 300 L of glutamic acid fermentation broth (CN103243131B specification example 7) is taken, the transmittance of the fermentation broth is 5.5%, the content of glutamic acid is 195 g / L, and the content of pyroglutamic acid is 5 g / L.

[0115] (2) The fermentation broth is pumped into a falling film evaporator for continuous concentration, the concentration temperature is 85°C, the vacuum degree is -0.09 Mpa, and the concentration is performed until the concentration of glutamic acid reaches 340 g / L; the concentration of pyroglutamic acid in the concentrated solution is detected to be 17 g / L.

[0116] (3) The concentrated solution is transferred into an isoelectric crystallization tank, concentrated sulfuric acid is added to adjust the pH to 3.2, and the temperature is reduced to 15°C by using refrigerated water; after crystal growth for 5 hours, wet glutamic acid and isoelectric mother liquor are obtained by centrifugal separation; the extraction yield of glutamic acid can reach 90%; the residual glutamic acid in the isoelectric mother liquor is detected to be 30 g / L, the pyroglutamic acid is 18 g / L, and the ammonium sulfate is 120 g / L.

[0117] (4) The isoelectric mother liquor of glutamic acid obtained by separation is filtered by using an ultrafiltration membrane to remove bacterial protein; 2% activated carbon is added to the filtrate, and the temperature is reduced to 50°C for 60 minutes; then, the decolorized liquid is obtained by plate and frame filtration.

[0118] (5) The decolorized liquid is adjusted to a pH of 3.2-3.3 by using sulfuric acid, and then enters a C-A type three-chamber single-pole membrane electrodialysis system which contains 1 pair of electrodes and 10 pairs of homogeneous ion exchange membranes (in which the anion exchange membrane is CMX, and the cation exchange membrane is AMX, Zhejiang Lanji Membrane Technology Co., Ltd.); the effective membrane area is 600 cm 2 ; the current density is controlled to be 20 mA / cm 2 ; the feeding flow rate is 10 L / h; and the concentrated water and the fresh water are collected respectively.

[0119] (6) The main component of the fresh water is glutamic acid, which is reused to the isoelectric crystallization tank.

[0120] (7) The concentrated water mainly contains pyroglutamic acid and ammonium sulfate; the concentrated water is evaporated to remove water, then dried to obtain a crude product, the crude product is dissolved in anhydrous ethanol, the ammonium sulfate is insoluble in anhydrous ethanol and is removed by filtration, the clear solution is concentrated by distillation, and the pyroglutamic acid is obtained by crystallization and drying, the content of pyroglutamic acid reaches 90%, and the yield reaches 80%.

[0121] In the example 1, the glutamic acid fermentation liquor is directly concentrated and isoelectrically separated without sterilization, resulting in high pyroglutamic acid content in the concentrated solution and the isoelectric mother liquor, and low glutamic acid extraction yield.

[0122] In the example 2, the glutamic acid isoelectrically separated without concentration and separation of most of the ammonium sulfate, resulting in the need for larger equipment investment for electrodialysis, and due to the high concentration of ammonium sulfate, incomplete separation, resulting in lower final pyroglutamic acid purity and yield.

[0123] Example 6: Optimization of glutamic acid isoelectric separation process conditions

[0124] Each time, 10 L of concentrated solution (example 4) with a glutamic acid concentration of 350 g / L and a pyroglutamic acid concentration of 10 g / L is poured into an isoelectric crystallization tank, the stirring speed is 100 rpm, the pH is continuously adjusted by adding concentrated sulfuric acid, the isoelectric point of glutamic acid is 3.22, and the solubility of glutamic acid is lowest at the isoelectric point, the pH of the material liquid is controlled between 3.2-3.3 by controlling the valve opening, the refrigerated water is introduced into the jacket, and the temperature of the crystallization material liquid needs to be controlled during the pH adjustment process, otherwise local temperature is too high, which is easy to form β-type glutamic acid and pyroglutamic acid by dehydration and cyclization, the cooling speed and the temperature of the crystallization tank material liquid are controlled by adjusting the opening of the refrigerated water inlet and outlet valve, and the glutamic acid yield and the content of each component in the mother liquor under different crystallization temperature and crystallization time conditions are shown in table 1:

[0125] Table 1

[0126]

[0127] As shown in table 1, under the same crystallization time conditions, the crystallization temperature has a significant effect on the extraction yield of glutamic acid, the lower the temperature (20-12 ℃), the lower the residual glutamic acid concentration in the mother liquor, and the higher the extraction yield, and when the temperature is continuously reduced to 10 ℃, there is no difference in the glutamic acid concentration in the mother liquor, the more the refrigerated water required, the more the cost increases, and the selection of 12-15 ℃ is more economical.

[0128] Under the same crystallization temperature conditions, the crystallization time affects the growth of the crystal, the longer the time (2-5 h), the more the crystal precipitates, and the higher the extraction yield, and when the crystallization time is continuously extended to 6 h, the yield does not continue to increase; the longer the crystallization time, the more the refrigerated water required, the more the cost increases, and the selection of 5-6 h is more economical.

[0129] Example 7: Optimization of electrodialysis separation process conditions

[0130] Each time 1 L of secondary mother liquor (Example 3) after decolorization filtration by activated carbon, glutamic acid 75 g / L, pyroglutamic acid 40 g / L, using sulfuric acid to adjust pH to 3.2-3.3, added to the fresh water storage tank of the electrodialysis system, tap water was added to the concentrated water storage tank, 30 g / L of sodium sulfate solution was added to the electrode water storage tank, the power supply and the respective circulating pumps were turned on to pump the feed liquid into each chamber of the electrodialysis system, the circulating pump feed flow rate and current were adjusted, and continuous operation was maintained under certain conditions, the glutamic acid and pyroglutamic acid concentrations and pH in the fresh water chamber were detected every 10 min, and the operation was stopped when the pyroglutamic acid concentration no longer changed, the operation time was recorded, and fresh water and concentrated water were collected respectively. The experimental results under different feed flow rates and current conditions are shown in Table 2:

[0131] Table 2

[0132]

[0133] Electric energy is the main mass transfer driving force in the electrodialysis process. Therefore, the size of the current density is directly related to the size of the ion migration driving force. When the current density is small, the working voltage is low, and the ion migration driving force is small, which cannot fully exert the efficiency of the electrodialysis device. Increasing the current density will increase the desalination efficiency, and the required processing time will be shortened. Polarization occurs when the material flows in the desalination chamber and the concentration chamber during electrodialysis. There is a stagnant layer between the ion exchange membrane and the water. Under the action of a direct current electric field, the solute undergoes directional migration. When the working current increases to a certain extent, the ions in the main body of the solution cannot be quickly replenished to the surface of the membrane. At this time, the ion concentration on the surface of the membrane tends to zero, causing a large number of water molecules in the stagnant layer to ionize and generate H + and OH - ions to carry charges. This phenomenon is called polarization. At this time, the current density also reaches a limit value, which is called the limiting current. In the electrodialysis process, if the operating current intensity is higher than the limiting current intensity, undesirable phenomena such as current efficiency decline, energy consumption increase, pH disorder, generation of a large number of bubbles (water electrolysis), membrane precipitation, scaling and blockage may occur, which seriously affect the normal operation of electrodialysis, reduce the efficiency of electrodialysis, and shorten the service life of the electrodialysis device. Therefore, selecting an appropriate current density is very important for the electrodialysis process.

[0134] During the operation of electrodialysis, when the flow rate is high, the impact on the membrane will be large, which may cause the membrane to leak and increase the energy consumption. When the flow rate is low, the turbulence degree of the liquid flow will be reduced, causing the diffusion stagnant layer to thicken, which is not conducive to the transmembrane migration of ions. Increasing the flow rate will shorten the processing time of the solution and improve the efficiency. Therefore, seeking an appropriate flow rate value is also crucial for the electrodialysis process.

[0135] While the application has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various modifications or changes can be made therein without departing from the spirit and scope thereof. Accordingly, it is intended that all such modifications and changes be included within the scope of the application as claimed.

Claims

1. A method for recovering pyroglutamic acid from glutamic acid fermentation broth, characterized in that, Includes the following steps: (1) The glutamic acid fermentation broth was centrifuged to remove the bacterial cells; (2) The supernatant obtained in step (1) was concentrated and then subjected to isoelectric separation to extract glutamic acid; (3) The isoelectric mother liquor of glutamic acid obtained in step (2) is concentrated and crystallized to separate ammonium sulfate; (4) The secondary mother liquor obtained in step (3) is decolorized and filtered, and then separated by electrodialysis to collect concentrated water and dilute water respectively; the dilute water contains glutamic acid, and the concentrated water contains pyroglutamic acid and ammonium sulfate; it is reused in an isoelectric crystallizer. (5) Recycle fresh water to the isoelectric separation process; evaporate concentrated water to remove moisture and dry to obtain crude product; dissolve crude product in anhydrous ethanol; remove ammonium sulfate, which is insoluble in anhydrous ethanol, by filtration; concentrate and crystallize the clear liquid to obtain pure pyroglutamic acid. Step (3) The separated isoelectric mother liquor of glutamic acid is pumped into an evaporator for concentration. The feed Baumé is 20-21 Be', the concentration temperature is 80-85℃, and the concentration is carried out to 1 / 3-1 / 4 of the volume of the isoelectric mother liquor of glutamic acid. Then the temperature is lowered to 30-50℃ and crystallized for 2-3 hours. Ammonium sulfate crystals and secondary mother liquor are then separated. The secondary mother liquor in step (4) contains 70-80 g / L of glutamic acid, 37-45 g / L of pyroglutamic acid, and 60-85 g / L of ammonium sulfate.

2. The method according to claim 1, characterized in that, Step (1) The glutamic acid content in the fermentation broth is 180-200 g / L, the pyroglutamic acid content is 4-6 g / L, the light transmittance of the fermentation broth is 5-7%, and after centrifugation to remove the cells, the light transmittance of the supernatant is >70%.

3. The method according to claim 1, characterized in that, In step (2), the supernatant is concentrated at 70-75℃ and under a vacuum of -0.08 to -0.09 MPa. The resulting concentrate contains 330-350 g / L of glutamic acid and 8-10 g / L of pyroglutamic acid.

4. The method according to claim 3, characterized in that, After the supernatant in step (2) is concentrated, the concentrate is transferred to a crystallization tank, the pH is adjusted to 3.2-3.3 with sulfuric acid, and then isoelectric separation is carried out at 12-15℃ for 5-6 hours to obtain wet glutamic acid and glutamic acid isoelectric mother liquor.

5. The method according to claim 1, characterized in that, Step (4) Add 1-2% activated carbon to the secondary mother liquor, decolorize at 40-50℃ for 40-60 min, and then filter through a plate and frame filter to obtain the decolorized liquor.

6. The method according to claim 5, characterized in that, The decolorizing solution was adjusted to pH 3.2–3.3 with sulfuric acid before being introduced into a three-chamber monopolar membrane electrodialysis system, with the current density controlled at 15–30 mA / cm². 2 The feed flow rate is 5-8 L / h, and electrodialysis separation is performed.

7. The method according to claim 6, characterized in that, The three-compartment unipolar membrane electrodialysis system is a CA-type system, comprising one pair of electrodes and five pairs of homogeneous ion exchange membranes. The anion exchange membrane is a polyethylene-grafted polystyrene quaternary ammonium type strongly basic anion exchange membrane, and the cation exchange membrane is a polyethylene-grafted polystyrene sulfonic acid type strongly acidic cation exchange membrane. The effective membrane area is 300 cm². 2 .

8. The method according to any one of claims 1-7, characterized in that, Glutamic acid fermentation broth is a microbial culture obtained by culturing Corynebacterium glutamicum or Short Bacillus glutamicum as fermentation strains.

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