Extraction method of high-purity glutamic acid

Abstract

The invention discloses an extraction method of high-purity glutamic acid, and belongs to the field of monosodium glutamate production industry. The method comprises the following steps: introducing glutamic acid fermentation liquor into an ultrafiltration membrane to obtain clear liquor and thallus concentrated liquor A; the thallus concentrated solution A enters a dialysis membrane to obtain dialysate and a thallus concentrated solution B; carrying out filter pressing on the thallus concentrated solution B to obtain fungi residues and filtrate; merging the filtrate and the thallus concentrated solution A; the dialysate enters a concentration membrane, a concentrated solution and membrane produced water are obtained, and the membrane produced water is dialysis water; the concentrated solution and the clear solution enter a continuous isoelectric crystallizer to be crystallized, and glutamic acid crystal slurry is discharged at the same time for crystallization; performing primary separation to obtain glutamic acid and isoelectric mother liquor A; the isoelectric mother liquor A is subjected to secondary separation, fine glutamic acid crystals and isoelectric mother liquor B are obtained, and the isoelectric mother liquor B enters a sewage treatment procedure; and fine glutamic acid crystals return to the continuous isoelectric crystallizer. The glutamic acid obtained by the method has the advantages of high yield, high product purity, high light transmittance and good color and luster, and is superior to the commonly used'concentration continuous isoelectric crystallization + crystal transformation 'process.

Description

Technical Field

[0001] The invention relates to a method for extracting high-purity glutamic acid, and belongs to the field of monosodium glutamate production industry. Background Art

[0002] Glutamic acid is an amphoteric amino acid with the lowest solubility at its isoelectric point (pI=3.22). Taking advantage of this property, acidic liquids such as sulfuric acid, high flux fractions from deionized water or hydrolyzate are added to the glutamate fermentation broth in industrial production to adjust the pH value of the fermentation broth to the isoelectric point of glutamate, so that glutamate crystals are precipitated. This is called isoelectric crystallization.

[0003] Due to the presence of impurities such as glucose, dextrin and other amino acids in the fermentation broth, which have a solubilizing effect on glutamate, practice has shown that the solubility of glutamate is lowest when the pH of the fermentation broth is adjusted to 3.1. Therefore, when isoelectric crystallization is used to extract glutamate in industrial production, the pH value of the fermentation broth is usually adjusted to 3.1.

[0004] Hydrolyzate refers to an acidic liquid obtained by hydrolyzing and filtering the liquid containing pyroglutamic acid produced during the extraction of glutamic acid or the refining of monosodium glutamate with sulfuric acid; it includes the hydrolyzate obtained by hydrolyzing the monosodium glutamate refining mother liquor with sulfuric acid, commonly known as the monosodium glutamate refining mother liquor hydrolyzate, and the hydrolyzate obtained by concentrating and hydrolyzing the glutamic acid crystallization mother liquor with sulfuric acid, commonly known as the crystallization mother liquor hydrolyzate.

[0005] There are two methods for isoelectric crystallization of glutamate: continuous isoelectric and batch isoelectric. Continuous isoelectric crystallization has the advantages of simple operation, stable product quality and extraction yield, and has become the preferred process for glutamate extraction. Industrial-scale isoelectric crystallization of glutamate needs to solve two key problems: one is to increase the extraction yield of isoelectric crystallization as much as possible, and the other is to increase the purity of glutamate crystals extracted by isoelectric crystallization as much as possible.

[0006] In conventional isoelectric crystallization of fermentation broth with bacterial cells, glutamic acid crystals have a certain range of particle size distribution. Coarse crystals are easy to separate from isoelectric mother liquor and have high purity, but fine crystals with a particle size of less than 100 μm are difficult to recover, resulting in a low extraction yield of isoelectric crystallization. Even if a horizontal screw centrifuge is used to recover fine crystals, the fine crystals carry a large number of bacterial cells and isoelectric mother liquor, resulting in a low purity of the extracted glutamic acid. Removing bacterial cells from the fermentation broth by high-speed centrifugation or membrane separation and then isoelectric crystallization can improve the glutamic acid extraction yield and product quality. The research of Xu Zhaohui et al. shows that the use of ultrafiltration membrane with a molecular weight cutoff of 10,000 can effectively remove large molecular proteins in the fermentation broth, and the purity of the extracted glutamic acid is increased by more than 1% (Xu Zhaohui Zhao Liang. Effect of ultrafiltration membrane removal of bacterial cells in L-glutamic acid fermentation broth on isoelectric extraction yield [J]. Membrane Science and Technology, 2000, 20 (3): 62-64). However, methods such as high-speed centrifugation and membrane filtration cannot obtain solid fungus residues, but can only obtain a bacterial cell concentrate with a moisture content of more than 90%. The moisture in the bacterial cell concentrate is actually the fermentation liquid. If this part of the fermentation liquid is not recovered, the glutamic acid extraction yield will be reduced. The bacterial cell concentrate is washed with water to recover the glutamic acid lost due to entrainment, but the washing water and the fermentation clear liquid obtained by high-speed centrifugation or membrane filtration are combined to reduce the glutamic acid concentration in the fermentation clear liquid, which is not only not conducive to isoelectric crystallization operation, but also because the volume of the discharged isoelectric mother liquor is greater than the volume of the fermentation liquid, the final isoelectric extraction yield of glutamic acid is reduced.

[0007] On the other hand, in order to realize continuous crystallization of glutamic acid, a multiple-effect evaporator is usually used for evaporation and concentration. The fermented liquid is concentrated by multiple-effect evaporation by 2.5 to 3 times. After the glutamic acid concentration reaches 28 to 33%, continuous isoelectric crystallization is performed, and then the crystals are cooled and separated to obtain glutamic acid crystals, and the isoelectric mother liquor is discharged; for example, the sterilization and extraction method of glutamic acid fermented liquid disclosed in Chinese patent CN109988790A adopts a plate evaporator with a concentration temperature of 80°C. Although the purity of the crystallized glutamic acid is high, the color is deepened, which brings difficulties to the subsequent refined production of monosodium glutamate; for another example, the fermentation and extraction process of glutamic acid disclosed in Chinese patent CN110923275B also adopts evaporation and concentration to obtain glutamic acid concentrate. The crystals obtained by continuous isoelectric concentration are dark in color, SO4 2-There are many impurities such as ions, which make it impossible to directly purify and produce monosodium glutamate. To solve this problem, the concentrated continuous isoelectric process is grafted with the "crystal conversion" technology, that is, the glutamic acid crystals are rehydrated into a crystal slurry, the pH is adjusted to between 4.0-4.5 with alkali and monosodium glutamate refining mother liquor, and then heated to above 90°C to transform the α-type crystals into β-type crystals, and the impurities are released during the crystal transformation process. Through the "crystal conversion" process, the purity, light transmittance and other quality indicators of glutamic acid are significantly improved, which is conducive to improving the quality of monosodium glutamate and reducing the consumption of activated carbon and steam in the process of monosodium glutamate refining. However, the crystal conversion process not only increases equipment investment, but also increases steam and power consumption, and inevitably loses some glutamic acid, and the glutamic acid yield decreases by about 2 percentage points.

[0008] At present, the mainstream process for glutamic acid production on an industrial scale is "concentrated continuous isoelectric crystallization + crystal transformation". This process first concentrates the glutamic acid fermentation broth by multi-effect evaporation to a glutamic acid mass concentration of 32-36%, and then performs subsequent continuous isoelectric crystallization and centrifugal separation to obtain α-glutamic acid crystals. The α-glutamic acid is then crystallized to form β-glutamic acid crystals. The crystal transformation mother liquor is subjected to evaporation concentration, sulfuric acid hydrolysis, filtration and other operations to obtain a hydrolyzate containing glutamic acid, and the hydrolyzate is recycled back to the continuous isoelectric crystallization process to adjust the pH value.

[0009] "Concentrated continuous isoelectric crystallization + crystal transformation" has at least the following defects:

[0010] (1) Low glutamic acid extraction yield: When the fermentation liquid is evaporated and concentrated, impurities such as bacteria and residual sugar are simultaneously concentrated. Impurities have a solubilizing effect on glutamic acid. In addition, the viscosity of the fermentation liquid increases after evaporation and concentration. The concentration of residual glutamic acid in the isoelectric mother liquor after isoelectric crystallization is as high as 2-2.5%. This is one of the reasons for the low yield of concentrated continuous isoelectric crystallization. In addition, due to the large amount of hydrolyzate added during the continuous isoelectric crystallization process, the volume of the discharged isoelectric mother liquor is about 1.6-1.8 times the volume of the concentrated fermentation liquid. A large amount of dissolved glutamic acid is discharged with the isoelectric mother liquor. This is the second reason for the low extraction yield of glutamic acid isoelectric crystallization. Usually, the glutamic acid extraction yield of the "concentrated continuous isoelectric crystallization + crystal conversion" process is between 85-88%;

[0011] (2) Low purity of crystallized glutamic acid: When the fermentation liquid is evaporated and concentrated, the bacteria, residual sugar and other impurities are concentrated simultaneously. In addition, the reaction between sugar and ammonia during evaporation and concentration causes the pigment to increase. The distribution of glutamic acid crystal particles is wide, and the bacteria cells and isoelectric mother liquor in the fermentation liquid are easily entrained during centrifugal separation, which affects the quality of the crystallized product, manifested as low purity and high impurity content. The data show that the purity of glutamic acid obtained by concentrated continuous isoelectric crystallization is about 90%, and the impurity SO4 2- Ion concentration ≥ 2.5%, glutamic acid crystals appear brown. After crystallization, the purity of glutamic acid increases to about 97%, and the impurity SO4 2-The ion concentration is around 0.1%, but the glutamic acid crystals still appear gray-brown;

[0012] (3) High consumption of production auxiliary materials such as sulfuric acid and liquid alkali: Due to the low solubility of glutamic acid in water, the crystallization process uses 2-4 times the mass of glutamic acid to prepare the glutamic acid obtained by centrifugation into a suspension, and then uses liquid alkali to adjust the pH of the suspension to 4.1-4.7; sulfuric acid needs to be added during the hydrolysis of the crystallization mother liquor and the concentration should be above 30%. In essence, part of the sulfuric acid added during the hydrolysis of the crystallization mother liquor is used to neutralize the liquid alkali added during the crystallization. This operation increases the consumption of sulfuric acid and liquid alkali. Therefore, when "concentrated continuous isoelectric crystallization + crystallization" is used, the sulfuric acid consumption per ton of glutamic acid is 350-400kg. Summary of the invention

[0013] [Technical issues]

[0014] The existing glutamic acid extraction technology has the following technical problems:

[0015] (1) Removing bacterial cells from the fermentation broth by methods such as high-speed centrifugation and membrane filtration can improve the purity of glutamic acid obtained by isoelectric crystallization. However, since part of the fermentation broth is entrained in the bacterial concentrate, the glutamic acid extraction yield is reduced. The bacterial concentrate obtained by methods such as high-speed centrifugation and membrane filtration is washed with water to recover the glutamic acid lost due to bacterial entrainment. However, the glutamic acid concentration in the fermentation supernatant is reduced after the washing water is combined with the fermentation supernatant obtained by high-speed centrifugation or membrane filtration. This is not only not conducive to continuous isoelectric crystallization operation, but also because the volume of the discharged isoelectric mother liquor is larger than the volume of the fermentation broth, the final isoelectric extraction yield of glutamic acid is reduced. Therefore, how to achieve both the removal of bacterial cells in the fermentation broth and the guarantee that the extraction yield is not reduced is one of the technical problems that need to be solved in glutamic acid extraction;

[0016] (2) Compared with the direct continuous isoelectric crystallization operation of the fermentation broth, the fermentation broth is subjected to multiple-effect evaporation and concentration to increase the glutamic acid concentration in the fermentation broth to 32-36% before continuous isoelectric crystallization. The advantages are high glutamic acid concentration and high crystal density in the continuous isoelectric crystallizer, so the continuous isoelectric crystallization operation is more stable. The disadvantage is that the purity of glutamic acid crystals is low due to evaporation and concentration, and crystal transfer is required. Therefore, how to achieve both stable continuous isoelectric crystallization and ensure the purity of glutamic acid and eliminate the crystal transfer process is another technical problem that needs to be solved in glutamic acid extraction.

[0017] [Technical solution]

[0018] In view of the defects and shortcomings of the prior art, the object of the present invention is to propose a method for extracting high-purity glutamic acid, so as to achieve the advantages of high glutamic acid crystal extraction yield, high product purity, high light transmittance, good color, white α-type appearance and low consumption of auxiliary materials.

[0019] To achieve the above purpose, the technical solution adopted is:

[0020] A method for extracting high-purity glutamic acid, the method comprising the following steps:

[0021] (1) The glutamate fermentation liquid enters the ultrafiltration membrane, and ultrafiltration is performed to obtain a clear liquid and a bacterial concentrate A;

[0022] (2) placing the bacterial cell concentrate A obtained in step (1) into a dialysis membrane, adding the membrane produced water from step (4) for dialysis, and obtaining a dialysate and a bacterial cell concentrate B;

[0023] (3) filtering the bacterial cell concentrate B obtained in step (2) to obtain bacterial residue and filtrate; the bacterial residue is directly used as a feed raw material; and the filtrate is combined with the bacterial cell concentrate A obtained in step (1);

[0024] (4) the dialysate obtained in step (2) is fed into a concentration membrane, and glutamic acid concentrate and membrane water are obtained through membrane concentration, and the membrane water is recycled to step (2) as dialysis water; the concentrate and the clear liquid in step (1) are combined and fed into a continuous isoelectric crystallizer in the form of continuous flow addition, the temperature of the continuous isoelectric crystallizer is kept at 20-40° C., the pH value is maintained at 3.1, and glutamic acid slurry is continuously discharged;

[0025] (5) continuously feeding the glutamic acid slurry discharged from step (4) into a cooling crystallizer, and further crystallizing and precipitating the glutamic acid in the cooling crystallizer;

[0026] (6) separating the glutamic acid slurry after crystallization and precipitation in step (5) to obtain high-purity glutamic acid and isoelectric mother solution A;

[0027] (7) The isoelectric mother liquor A obtained in step (6) is subjected to secondary separation to obtain fine glutamic acid crystals and isoelectric mother liquor B, and the isoelectric mother liquor B enters the subsequent sewage treatment process; the fine glutamic acid crystals return to step (4) and enter the continuous isoelectric crystallizer.

[0028] In one embodiment, the mass concentration of glutamate in the glutamate fermentation broth in step (1) is 18-22%.

[0029] In one embodiment, the ultrafiltration membrane in step (1) is a ceramic ultrafiltration membrane or an organic ultrafiltration tubular membrane.

[0030] In one embodiment, the ultrafiltration membrane in step (1) has a molecular weight cutoff of 100,000-500,000 Daltons, and the ultrafiltration concentration multiple is 8-15 times, that is, the mass of the bacterial concentrate A is 1 / 15-1 / 8 of the mass of the fermentation broth.

[0031] In one embodiment, when the dialysis membrane in step (2) produces insufficient water, process water is added to perform dialysis.

[0032] In one embodiment, the dialysis membrane in step (2) is a ceramic dialysis membrane or an organic dialysis tube membrane.

[0033] In one embodiment, the molecular weight cutoff of the dialysis membrane in step (2) is 100,000-500,000 Daltons.

[0034] In one embodiment, the mass of the dialysis water in step (2) is 1-4 times the mass of the bacterial concentrate A, and the dialysis water is added in 1-3 times; preferably, it is added in 3 times.

[0035] In one embodiment, the filtration in step (3) is performed using a plate and frame or chamber filter press.

[0036] In one embodiment, the concentration membrane in step (4) is a high pressure nanofiltration membrane with a molecular weight cut-off of 100-500 Daltons.

[0037] In one embodiment, the mass concentration of glutamate in the glutamate concentrate obtained by membrane concentration in step (4) is increased to 18-27%.

[0038] In one embodiment, the step (4) of maintaining the pH value at 3.1 is performed by continuously adding sulfuric acid, one or a mixture of monosodium glutamate mother liquor hydrolyzate to maintain the pH value at 3.1.

[0039] In one embodiment, the monosodium glutamate refining mother liquor hydrolyzate refers to an acidic liquid monosodium glutamate refining mother liquor obtained by hydrolyzing with sulfuric acid and filtering the mother liquor containing pyroglutamic acid produced in the monosodium glutamate refining process as a raw material.

[0040] In one embodiment, the cooling crystallization in step (5) uses chilled water to reduce the temperature of the glutamic acid slurry to 2-10° C. and maintain it for 4-10 hours.

[0041] In one embodiment, the primary separation in step (6) is performed using a cone basket filter centrifuge, and the filter pore size of the centrifuge is 0.05-0.2 mm.

[0042] In one embodiment, the secondary separation in step (7) is performed using a decanter centrifuge at a rotation speed of 4000-6000 rpm.

[0043] The present invention also provides a method for simultaneously improving the purity and light transmittance of glutamic acid, the method comprising the following steps:

[0044] (1) The glutamate fermentation liquid enters the ultrafiltration membrane, and ultrafiltration is performed to obtain a clear liquid and a bacterial concentrate A;

[0045] (2) placing the bacterial cell concentrate A obtained in step (1) into a dialysis membrane, adding the membrane produced water from step (4) for dialysis, and obtaining a dialysate and a bacterial cell concentrate B;

[0046] (3) filtering the bacterial cell concentrate B obtained in step (2) to obtain bacterial residue and filtrate; the bacterial residue is directly used as a feed raw material; and the filtrate is combined with the bacterial cell concentrate A obtained in step (1);

[0047] (4) the dialysate obtained in step (2) is fed into a concentration membrane, and glutamic acid concentrate and membrane water are obtained through membrane concentration, and the membrane water is recycled to step (2) as dialysis water; the concentrate and the clear liquid in step (1) are combined and fed into a continuous isoelectric crystallizer in the form of continuous flow addition, the temperature of the continuous isoelectric crystallizer is kept at 20-40° C., the pH value is maintained at 3.1, and glutamic acid slurry is continuously discharged;

[0048] (5) continuously feeding the glutamic acid slurry discharged from step (4) into a cooling crystallizer, and further crystallizing and precipitating the glutamic acid in the cooling crystallizer;

[0049] (6) separating the glutamic acid slurry after crystallization and precipitation in step (5) to obtain high-purity glutamic acid and isoelectric mother solution A;

[0050] (7) The isoelectric mother liquor A obtained in step (6) is subjected to secondary separation to obtain fine glutamic acid crystals and isoelectric mother liquor B, and the isoelectric mother liquor B enters the subsequent sewage treatment process; the fine glutamic acid crystals return to step (4) and enter the continuous isoelectric crystallizer.

[0051] The present invention also provides the application of the above-mentioned method for extracting high-purity glutamic acid or the method for simultaneously improving the purity and light transmittance of glutamic acid in the production and processing of glutamic acid.

[0052] [Beneficial Effects]

[0053] The glutamic acid extracted by the present invention has a white α-type appearance, a dry basis purity of ≥98.0%, a light transmittance of ≥65%, and SO4 2- ions <0.1%, extraction yield>90%, glutamic acid extraction yield and glutamic acid quality are better than the "concentrated continuous isoelectric crystallization + crystal transformation" process commonly used in the monosodium glutamate industry; compared with the "concentrated continuous isoelectric crystallization + crystal transformation" technology currently used in the monosodium glutamate industry, the present invention has the following advantages:

[0054] (1) The present invention eliminates the operations of multi-effect evaporation concentration of the fermentation liquid and glutamic acid crystallization, thereby avoiding the problems of glutamic acid coking to form pyroglutamic acid and the increase of pigment in the fermentation liquid due to the reaction of sugar and ammonia, which occur in the multi-effect evaporation concentration and crystallization operations. It can not only ensure a high extraction yield of glutamic acid, but also ensure the chromaticity of glutamic acid crystals, and reduce the consumption of activated carbon in the later monosodium glutamate refining operation;

[0055] (2) Ultrafiltration is used to remove impurities such as bacterial cells and macromolecular proteins in the glutamic acid fermentation broth, which creates good crystallization conditions for isoelectric crystallization, is conducive to reducing the content of residual glutamic acid in the isoelectric mother liquor, improving the glutamic acid extraction yield, and improving the purity of glutamic acid;

[0056] (3) After ultrafiltration, part of glutamic acid is entrained in the bacterial concentrate A. The glutamic acid remaining in the bacterial concentrate A is recovered by dialysis membrane, which is beneficial to improving the glutamic acid extraction yield; a small amount of glutamic acid remains in the bacterial concentrate B. The filtrate is recovered by pressure filtration and returned to the front of the dialysis membrane. After being combined with the bacterial concentrate A, the glutamic acid is recovered by dialysis, which is beneficial to improving the glutamic acid extraction yield;

[0057] (4) The glutamic acid slurry after cooling and crystallization is separated once. For the first time, a cone blue filter centrifuge is used to separate and recover coarse glutamic acid particles with high purity and less entrained mother liquor, which greatly reduces the content of impurities such as pigments, miscellaneous proteins, and sulfate ions in glutamic acid.

[0058] (5) The glutamic acid slurry after cooling and crystallization is subjected to secondary separation. The second separation adopts a horizontal screw sedimentation centrifuge to recover glutamic acid to the greatest extent, reduce the residual glutamic acid in the isoelectric mother liquor B, and improve the glutamic acid yield; the fine glutamate crystals recovered by the secondary separation are returned to the continuous isoelectric crystallizer to continue crystallization growth, and at the same time, the crystal slurry density in the continuous isoelectric crystallizer is also increased, which is conducive to the long-term stable operation of the continuous isoelectric crystallization. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. The following specific implementation methods further describe the present invention.

[0060] The glutamate fermentation liquid involved in the embodiment of the present invention refers to a liquid containing 18-22% glutamate obtained by microbial fermentation using starch sugar as the main raw material (conventional glutamate fermentation liquid in the prior art).

[0061] Example 1

[0062] A method for extracting high-purity glutamic acid comprises the following steps:

[0063] (1) The fermentation broth has a glutamic acid mass concentration of 18%, and the glutamic acid fermentation broth is ultrafiltered using a ceramic membrane with a molecular weight cutoff of 500,000 Daltons to obtain a clear liquid and a bacterial concentrate A, and the ultrafiltration concentration multiple is 15 times;

[0064] (2) adding dialysis water (1 times the mass of the bacterial concentrate A) to the bacterial concentrate A twice, wherein the dialysis water comes from the membrane water produced in step (4), and dialyzing is performed twice using a ceramic membrane with a molecular weight cutoff of 500,000 Daltons to obtain a dialysate and a bacterial concentrate B;

[0065] (3) The bacterial concentrate B obtained in step (2) is filtered using a chamber filter press at a pressure of 1.0 MPa to obtain bacterial residue and filtrate, and the bacterial residue is directly sold as a feed raw material; the filtrate is combined with the bacterial concentrate A obtained in step (1);

[0066] (4) using a high-pressure nanofiltration membrane with a molecular weight cutoff of 100 Daltons to concentrate the dialysate obtained in step (2) to a concentration of glutamic acid to 18%, and the membrane produced water is reused in step (2) as dialysate water; the concentrated solution and the clear solution in step (1) are combined and continuously fed into a continuous isoelectric crystallizer at a temperature of 20° C. and a pH of 3.1, and sulfuric acid is continuously fed to maintain the pH in the continuous isoelectric crystallizer at 3.1, and the clear solution, concentrated solution, and sulfuric acid are continuously fed into the continuous crystallizer, and glutamic acid slurry is continuously discharged;

[0067] (5) the glutamic acid slurry formed in step (4) continuously enters cooling crystallization, and the temperature of the glutamic acid slurry is reduced to 2° C. with chilled water and maintained for 4 hours, so that the glutamic acid further crystallizes and precipitates;

[0068] (6) using a cone blue filter centrifuge with a filter mesh size of 0.05 mm to perform a primary separation on the glutamic acid slurry after cooling and crystallization in step (5) to obtain high-purity glutamic acid and isoelectric mother liquor A;

[0069] (7) A horizontal screw sedimentation centrifuge with a rotation speed of 6000 rpm is used to perform secondary separation on the isoelectric mother liquor A obtained in step (6) to obtain fine glutamic acid crystals and isoelectric mother liquor B. The isoelectric mother liquor B enters the subsequent sewage treatment process, and the fine glutamic acid crystals return to step (4) and enter the continuous isoelectric crystallizer.

[0070] The glutamic acid produced according to this embodiment has the appearance of white α-type crystals, with a dry basis purity of 98.0%, a light transmittance of 65%, and SO4 2- The ion concentration was 0.1% and the glutamic acid extraction yield was 90%.

[0071] Comparative Example 1

[0072] The method for extracting glutamic acid by concentrated continuous isoelectric + crystallization process comprises the following steps:

[0073] The fermentation liquid with a mass concentration of 18% glutamic acid was concentrated to a glutamic acid concentration of 36% by using a multiple-effect evaporator with bacteria evaporation, and continuous isoelectric crystallization was performed at 20°C and pH 3.1, and then the temperature was lowered to 2°C, and the concentrated isoelectric glutamic acid was obtained by centrifugation using a horizontal screw sedimentation centrifuge with a rotation speed of 6000rpm. Then, the concentrated isoelectric glutamic acid was added with 2 times of tap water, and the pH was adjusted to 4.1 by adding liquid alkali, and the crystallization was completed by heating to 90°C, and then the crystallization was completed by cooling to 2°C, and the crystallized glutamic acid was obtained by filtration. The quality and yield analysis of the concentrated isoelectric glutamic acid and the crystallized glutamic acid are shown in Table 1.

[0074] Table 1 Comparison of glutamic acid quality and yield of two extraction processes

[0075]

[0076] Example 2

[0077] A method for extracting high-purity glutamic acid comprises the following steps:

[0078] (1) The fermentation broth has a glutamic acid mass concentration of 20.5%, and the glutamic acid fermentation broth is ultrafiltered using a ceramic membrane with a molecular weight cutoff of 200,000 Daltons to obtain a clear liquid and a bacterial concentrate A, and the ultrafiltration concentration multiple is 12 times;

[0079] (2) dialyzing the bacterial concentrate A with a ceramic membrane having a molecular weight cutoff of 200,000 Daltons, wherein the dialyzate water is the membrane produced water and process water from step (4), and the mass of the dialyzate water is 3 times the mass of the bacterial concentrate A. The dialyzate water is added in 3 times, and each time the dialyzate water is added with 1 times the mass of the bacterial concentrate A, and the dialyzate and the bacterial concentrate B are obtained through dialysis;

[0080] (3) using a chamber filter press to filter the bacterial concentrate B obtained in step (2) at a pressure of 1.0 MPa to obtain bacterial residue and filtrate, and the bacterial residue is directly sold as a feed raw material; the filtrate is combined with the bacterial concentrate A obtained in step (1);

[0081] (4) using a high pressure nanofiltration membrane with a molecular weight cutoff of 150 Daltons, the dialysate obtained in step (2) is concentrated to obtain a concentrate with a glutamic acid mass concentration of 21% and membrane water, and the membrane water is reused in step (2) as dialysate water; the concentrate and the clear liquid in step (1) are combined and continuously fed into a continuous isoelectric crystallizer at a temperature of 35° C. and a pH of 3.1, and a mixed solution of sulfuric acid and monosodium glutamate mother liquor hydrolyzate is continuously fed, the mass mixing ratio of sulfuric acid and monosodium glutamate mother liquor hydrolyzate is 1:0.5, and the pH in the continuous isoelectric crystallizer is maintained at 3.1; the clear liquid, the concentrate, sulfuric acid, and the monosodium glutamate mother liquor hydrolyzate are continuously fed into the continuous crystallizer, and the glutamic acid slurry is continuously discharged;

[0082] (5) the glutamic acid slurry formed in step (4) continuously enters cooling crystallization, and in the cooling crystallizer, the temperature of the glutamic acid slurry is reduced to 8° C. with chilled water and maintained for 6 hours, so that the glutamic acid further crystallizes and precipitates;

[0083] (6) using a cone basket filter centrifuge with a filter mesh size of 0.1 mm to perform a primary separation on the glutamic acid slurry after cooling and crystallization in step (5) to obtain high-purity glutamic acid and isoelectric mother liquor A;

[0084] (7) using a decanter centrifuge with a rotation speed of 4500 rpm to perform secondary separation on the isoelectric mother liquor A obtained in step (7) to obtain fine glutamic acid crystals and isoelectric mother liquor B, the isoelectric mother liquor B enters the subsequent sewage treatment process, and the fine glutamic acid crystals return to step (5) and enter the continuous isoelectric crystallizer;

[0085] The glutamic acid produced according to this embodiment has a white α-type appearance, a dry basis purity of 98.2%, a light transmittance of 66.2%, and SO4 2- ions 0.08%, extraction yield 91.1%.

[0086] Comparative Example 2

[0087] The method for extracting glutamic acid by concentrated continuous isoelectric + crystallization process comprises the following steps:

[0088] The fermentation liquid with a glutamic acid mass concentration of 20.5% was concentrated to a glutamic acid concentration of 36% by using a multi-effect evaporator with bacteria evaporation, and continuous isoelectric crystallization was performed at 35°C and pH 3.1, and then the temperature was lowered to 8°C, and the concentrated isoelectric glutamic acid was obtained by centrifugation in a horizontal screw sedimentation centrifuge with a rotation speed of 4500rpm. Then, the concentrated isoelectric glutamic acid was added with 2 times of tap water, and the pH was adjusted to 4.1 by adding liquid alkali, and the crystallization was completed by heating to 90°C, and then the temperature was lowered to 8°C, and the crystallized glutamic acid was obtained by filtration. The quality and yield analysis of the concentrated isoelectric glutamic acid and the crystallized glutamic acid are shown in Table 2.

[0089] Table 2 Comparison of glutamic acid quality and yield of two extraction processes

[0090]

[0091] Example 3

[0092] A method for extracting high-purity glutamic acid comprises the following steps:

[0093] (1) The fermentation broth has a glutamic acid mass concentration of 22%, and the fermentation broth is ultrafiltered using an organic tubular membrane with a molecular weight cutoff of 100,000 Daltons to obtain a clear liquid and a bacterial concentrate A, with the ultrafiltration concentration multiple being 8 times;

[0094] (2) dialyzing the bacterial concentrate A using an organic tubular membrane with a molecular weight cutoff of 100,000 Daltons, wherein the dialyzate water is the membrane produced water from step (4), and the mass of the dialyzate water is 4 times the mass of the bacterial concentrate A. The dialyzate water is added in two equal portions, and dialyzate and bacterial concentrate B are obtained through dialysis;

[0095] (3) using a chamber filter press to filter the bacterial concentrate B obtained in step (2) at a pressure of 1.0 MPa to obtain bacterial residue and filtrate, and the bacterial residue is directly sold as a feed raw material; the filtrate is combined with the bacterial concentrate A obtained in step (1);

[0096] (4) using a high-pressure nanofiltration membrane with a molecular weight cutoff of 500 Daltons to concentrate the dialysate obtained in step (2) to obtain a concentrated solution with a glutamic acid mass concentration of 27% and membrane water, and the membrane water is reused in step (2) as dialysate water; the concentrated solution and the clear solution in step (1) are combined and continuously fed into a continuous isoelectric crystallizer at a temperature of 40° C. and a pH of 3.1, and sulfuric acid is continuously fed to maintain the pH in the continuous isoelectric crystallizer at 3.1, so that glutamic acid crystals are precipitated to form glutamic acid slurry, and the clear solution, concentrated solution and sulfuric acid are continuously fed into the continuous crystallizer, and the glutamic acid slurry is continuously discharged;

[0097] (5) the glutamic acid slurry formed in step (4) continuously enters cooling crystallization, and in the cooling crystallizer, the temperature of the glutamic acid slurry is reduced to 10° C. with chilled water and maintained for 10 hours, so that the glutamic acid further crystallizes and precipitates;

[0098] (6) using a cone basket filter centrifuge with a filter mesh size of 0.1 mm, subjecting the glutamic acid slurry after cooling and crystallization in step (5) to a primary separation to obtain high-purity glutamic acid and isoelectric mother liquor A;

[0099] (7) The isoelectric mother liquor A obtained in step (6) is subjected to secondary separation using a decanter centrifuge with a rotation speed of 4000 rpm to obtain fine glutamic acid crystals and isoelectric mother liquor B. The isoelectric mother liquor B enters a subsequent sewage treatment process, and the fine glutamic acid crystals return to step (4) and enter a continuous isoelectric crystallizer.

[0100] The glutamic acid produced according to this embodiment has a white α-type appearance, a dry basis purity of 98.2%, a light transmittance of 67.3%, and SO4 2- The ion content is 0.05% and the extraction yield is 91.8%.

[0101] Comparative Example 3

[0102] The method for extracting glutamic acid by concentrated continuous isoelectric + crystallization process comprises the following steps:

[0103] The fermentation liquid with a glutamic acid mass concentration of 22% was concentrated to a glutamic acid concentration of 36% by using a multi-effect evaporator with bacteria evaporation, and continuously isoelectric crystallized at 40°C and pH 3.1, and then cooled to 10°C and centrifuged in a horizontal screw sedimentation centrifuge with a rotation speed of 4000rpm to obtain concentrated isoelectric glutamic acid. Then, the concentrated isoelectric glutamic acid was added with 2 times of tap water, and liquid alkali was added to adjust the pH to 4.1, and heated to 90°C to complete the crystallization, and then cooled to 10°C and filtered to obtain the crystallized glutamic acid. The quality and yield analysis of concentrated isoelectric glutamic acid and crystallized glutamic acid are shown in Table 3.

[0104] Table 3 Comparison of glutamic acid quality and yield of two extraction processes

[0105]

[0106] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for extracting high-purity glutamic acid, characterized in that: The method comprises the following steps: (1) The glutamate fermentation liquid enters the ultrafiltration membrane, and ultrafiltration is performed to obtain a clear liquid and a bacterial concentrate A; (2) placing the bacterial cell concentrate A obtained in step (1) into a dialysis membrane, adding the membrane produced water from step (4) for dialysis, and obtaining a dialysate and a bacterial cell concentrate B; (3) filtering the bacterial cell concentrate B obtained in step (2) to obtain bacterial residue and filtrate; the bacterial residue is directly used as a feed raw material; and the filtrate is combined with the bacterial cell concentrate A obtained in step (1); (4) the dialysate obtained in step (2) is fed into a concentration membrane, and glutamic acid concentrate and membrane water are obtained through membrane concentration, and the membrane water is recycled to step (2) as dialysis water; the concentrate and the clear liquid in step (1) are combined and fed into a continuous isoelectric crystallizer in the form of continuous flow addition, the temperature of the continuous isoelectric crystallizer is kept at 20-40° C., the pH value is maintained at 3.1, and glutamic acid slurry is continuously discharged; (5) continuously feeding the glutamic acid slurry discharged from step (4) into a cooling crystallizer, and further crystallizing and precipitating the glutamic acid in the cooling crystallizer; (6) separating the glutamic acid slurry after crystallization and precipitation in step (5) to obtain high-purity glutamic acid and isoelectric mother solution A; (7) The isoelectric mother liquor A obtained in step (6) is subjected to secondary separation to obtain fine glutamic acid crystals and isoelectric mother liquor B, and the isoelectric mother liquor B enters the subsequent sewage treatment process; the fine glutamic acid crystals return to step (4) and enter the continuous isoelectric crystallizer.

2. The method according to claim 1, characterized in that The mass concentration of glutamic acid in the glutamic acid fermentation broth in step (1) is 18-22%.

3. The method according to claim 1, characterized in that The ultrafiltration membrane of step (1) has a molecular weight cutoff of 100,000-500,000 Daltons, and the ultrafiltration concentration multiple is 8-15 times, that is, the mass of the bacterial concentrate A is 1 / 15-1 / 8 of the mass of the fermentation broth.

4. The method according to claim 1, characterized in that: The dialysis membrane in step (2) is a ceramic dialysis membrane or an organic dialysis tube membrane.

5. The method according to claim 1, characterized in that The molecular weight cut-off of the dialysis membrane in step (2) is 100,000-500,000 Daltons.

6. The method according to claim 1, characterized in that The concentration membrane in step (4) is a high pressure nanofiltration membrane with a molecular weight cut-off of 100-500 Daltons.

7. The method according to claim 1, characterized in that In step (4), the mass concentration of glutamate in the glutamate concentrate obtained by membrane concentration is increased to 18-27%.

8. The method according to claim 1, characterized in that In step (5), the cooling crystallization uses chilled water to reduce the temperature of the glutamic acid slurry to 2-10° C. and maintains it for 4-10 hours.

9. A method for simultaneously improving the purity and transmittance of glutamic acid, characterized in that: The method comprises the following steps: (1) The glutamate fermentation liquid enters the ultrafiltration membrane, and ultrafiltration is performed to obtain a clear liquid and a bacterial concentrate A; (2) placing the bacterial cell concentrate A obtained in step (1) into a dialysis membrane, adding the membrane produced water from step (4) for dialysis, and obtaining a dialysate and a bacterial cell concentrate B; (3) filtering the bacterial cell concentrate B obtained in step (2) to obtain bacterial residue and filtrate; the bacterial residue is directly used as a feed raw material; and the filtrate is combined with the bacterial cell concentrate A obtained in step (1); (4) the dialysate obtained in step (2) is fed into a concentration membrane, and glutamic acid concentrate and membrane water are obtained through membrane concentration, and the membrane water is recycled to step (2) as dialysis water; the concentrate and the clear liquid in step (1) are combined and fed into a continuous isoelectric crystallizer in the form of continuous flow addition, the temperature of the continuous isoelectric crystallizer is kept at 20-40° C., the pH value is maintained at 3.1, and glutamic acid slurry is continuously discharged; (5) continuously feeding the glutamic acid slurry discharged from step (4) into a cooling crystallizer, and further crystallizing and precipitating the glutamic acid in the cooling crystallizer; (6) separating the glutamic acid slurry after crystallization and precipitation in step (5) to obtain high-purity glutamic acid and isoelectric mother solution A; (7) The isoelectric mother liquor A obtained in step (6) is subjected to secondary separation to obtain fine glutamic acid crystals and isoelectric mother liquor B, and the isoelectric mother liquor B enters the subsequent sewage treatment process; the fine glutamic acid crystals return to step (4) and enter the continuous isoelectric crystallizer.

10. Use of the method according to any one of claims 1 to 8 or the method for improving the purity and transmittance of glutamic acid according to claim 9 in the production and processing of glutamic acid.

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