WO2008134937A1

WO2008134937A1 - A process for producing the ctystal of glutamic acid

Info

Publication number: WO2008134937A1
Application number: PCT/CN2008/000875
Authority: WO
Inventors: Dehui Wang; Dongshu Jia
Original assignee: Changchun Dacheng Industrial Group Company Limited
Priority date: 2007-04-29
Filing date: 2008-04-29
Publication date: 2008-11-13
Also published as: CN101293849A; CN101293849B

Abstract

Disclosed is a process for producing the crystal of glutamic acid, which includes filtering the fermented liquid of glutamic acid by ceramic membrane to remove the thallus in the fermented liquid of glutamic acid, then making the obtained clearing fermented liquid of glutamic acid gradient temperature lowering crystallization using batch continuous isoelectric method in the crystallizing tank, and sulfuric acid is added in the crystallizing tank by calandria porous showering method to reduce pH value, wherein the feed liquid is discharged continuously into the lower-stage tank using the mode of overflow on the top of tank, and in the lower-stage tank 2/3 of feed liquid is from the upper-stage tank by overflow and 1/3 of feed liquid is concentrated liquid. The crystal of glutamic acid obtained by the method is the alpha mode.

Description

Production method of glutamic acid crystallization

The present invention relates to a process for producing glutamic acid crystals. Specifically, the present invention relates to an improved process for producing glutamic acid crystals by isoelectric crystallization using a fermentation process for producing glutamic acid. Background technique

Glutamate is mainly used in the production of MSG. The most widely used method for the production of glutamic acid at home and abroad is the fermentation method. There are various processes for extracting glutamic acid from the fermentation broth. The main methods are: Extraction of glutamic acid by ion exchange, extraction of glutamic acid by zinc salt method, extraction of glutamic acid by hydrochloride method, and extraction of glutamic acid by electrodialysis. The isoelectric extraction of glutamic acid is based on the following properties of glutamic acid: At the isoelectric point pH, the positive and negative charges of glutamic acid are equal, the total charge is 0, forming a dipolar ion, its solubility at this time. The smallest, and precipitated into a crystal form. The specific extraction methods can be divided into intermittent isoelectric method and continuous isoelectric method. The advantages of intermittent isoelectric method are that the process is mature, the crystal particles are relatively uniform, and the disadvantage is that it cannot be continuously operated and the efficiency is low. The advantage of continuous isoelectric crystallization is continuous discharge. Each stage of the crystallization tank is set to have a fixed isoelectric pH value, which is easy to control, and the disadvantage is that the particles are not uniform; in the step of lowering the pH value of the crystallization tank and adding sulfuric acid, the conventional process directly connects the sulfuric acid pipeline to the crystallization tank, When sulfuric acid is added, it is prone to local supersaturation and produces β-type crystal. The β-type crystal is not easy to be centrifugally dehydrated, and the bulk density is small, which brings certain difficulties to the later packaging and transportation, and also affects α once β-form crystal is formed. Formation of the type. For example, the patent application CN88103158 of the Tianjin Light Industry Design Institute, the patent ZL96116404.2 of Wuxi University of Light Industry and the patent ZL02109965.0 of Liu Shizhai all use the continuous isoelectric crystallization method to extract glutamic acid, but still fail to overcome the above defects. The inventors have developed a novel isoelectric crystallization method which employs a combination of continuous and intermittent methods and removes the species in the fermentation broth prior to crystallization. The purity of glutamic acid obtained by this method is over 98.5%, the extraction yield is 93%, the sulfate is less than 0.3 mg/L, the color of the finished product is good, the crystal grains are uniform, and the bacteria and secondary condensate produced in the production. The mother liquor has been fully utilized, which not only solves the problem of sewage discharge that has been plaguing the industry, but also turns waste into treasure and creates new economic value.

Summary of the invention

The present invention provides a method for producing glutamic acid crystals by using a batch-continuous phase junction The combined isoelectric crystallization method extracts glutamic acid from a glutamic acid fermentation broth, which is characterized in that the cells in the fermentation broth are first removed before isoelectric crystallization to avoid the appearance of fine crystals. In particular, the present invention provides a method of producing glutamic acid crystals, the method comprising the steps of:

(1) sterilizing the glutamic acid fermentation broth and removing the cells by membrane filtration to obtain a clarified glutamic acid fermentation broth;

(2) evaporating and concentrating the above glutamic acid fermentation liquid to obtain a glutamic acid concentrate;

(3) performing a crystallization operation in a continuous-batch manner, providing a first-stage crystallization tank and a plurality of secondary crystallization tanks, and adding the obtained glutamic acid concentrate to a first-stage crystallization tank for crystallization; The acid stream is continuously overflowed from the primary crystallization tank to the secondary crystallization tank, and the batch crystallization operation is performed in the secondary crystallization tank, and the crystallization operation is performed by gradient cooling crystallization;

(4) The crystal particles obtained in the previous step are sedimented by a sedimentation tank, centrifuged, washed, and dried to obtain glutamic acid crystals. Preferably, in the crystallization operation carried out in the secondary crystallization tank, 2/3 of the total feed amount overflows from the primary crystallization tank, and the remaining 1/3 is the glutamic acid concentrate obtained in the second step. In the method of the present invention, the acidity of the raw material glutamic acid fermentation liquid used is usually about 7-8. Before filtering the glutamic acid fermentation liquid, first, an acid, preferably a mineral acid such as sulfuric acid or hydrochloric acid, etc., more preferably sulfuric acid, should be used. For example, concentrated sulfuric acid adjusts the pH of the glutamic acid fermentation broth to 5.5-6.0, preferably about

In the method of the present invention, the filtration step of the glutamic acid fermentation broth may be carried out by a membrane filtration method, for example, using an inorganic ceramic membrane or an ultrafiltration membrane to remove impurities such as remaining bacteria or proteins. It is preferred to use an inorganic ceramic membrane having a molecular weight cutoff of 300 kD. The filtered cells are dried to obtain a bacterial protein, which is a highly nutritious substance and is widely used, for example, for preparing feed or fertilizer, and can obtain a protein feed or a high-efficiency fertilizer. The inorganic ceramic membrane is obtained by sintering an oxide such as alumina, titania or zirconia at a high temperature, and is a porous ceramic filter material having a porous structure in which the porous support layer, the filter layer and the microporous membrane layer are asymmetrically distributed. Filtration accuracy can range from microfiltration to ultrafiltration to sodium filtration. Ceramic membrane filtration is a fluid separation process in the form of "cross-flow filtration" in which a raw material liquid flows at a high speed in a membrane tube, and a clarified permeate containing a small molecular component is driven through the membrane in a direction perpendicular thereto. Macromolecule The turbid concentrate of the components is trapped by the membrane, thereby allowing the fluid to be separated, concentrated and purified. Compared with traditional filter materials, inorganic ceramic membranes have many advantages, such as excellent chemical stability, high temperature resistance, high mechanical strength, uniform pore size distribution, high separation precision, and easy cleaning. Widely used in pharmaceutical, bioengineering, electronics and other industries. When using the inorganic ceramic membrane for filtration operation, the operating temperature and pressure can be carried out according to the instructions of the product manual or the normal operating conditions. Generally, the maximum temperature of the operation process is about 85 °C, the maximum pressure is generally not more than 7.5 kg, and should be anti-vibration. Prevent the drama from being hot. Practice has proved that the inorganic ceramic membrane has excellent chemical stability, high temperature resistance, high mechanical strength, uniform pore size distribution, high separation precision, and β-form crystal is not easy to appear in the clean process. The purity of the separation product is high and it is easier to concentrate. In the method of the present invention, wherein the evaporation concentration of the glutamic acid fermentation liquid can be carried out by a conventional vacuum concentration method, preferably by a multi-effect evaporation method, for example, a four-effect evaporation method, when using a four-effect evaporation method and apparatus, The conditions for four-effect evaporation can be, for example, 9 (TC:, 80 ° C, 70 ° C, and 60 ° C. The concentration of the concentrated glutamic acid concentrate can reach 13 to 22 Be ^Q , preferably 17 to 22 Be ^Q . The secondary condensate obtained in the above concentration evaporation step is a high nitrogen source, and can be applied to the fermentative production of amino acids such as lysine, threonine and glutamic acid to provide a nitrogen source for the fermentation process. In the method, the crystallization operation is carried out in a continuous-batch manner. A primary crystallization tank and a plurality of secondary crystallization tanks may be provided, for example, 2-4 secondary crystallization tanks, preferably 3 secondary crystallization tanks. The obtained glutamic acid concentrate stream is added to the first-stage crystallization tank for crystallization; then the glutamic acid-containing stream is continuously overflowed from the primary crystallization tank to the secondary crystallization tank, and intermittently incubated in the secondary crystallization tank Crystal operation. In this In the step (3) of the method, the glutamic acid concentrate is continuously flowed into the first-stage crystallization tank, and small crystals start to appear when the pH of the glutamic acid clear solution is adjusted to the isoelectric point. In the meantime, the temperature in the first-stage crystallizing tank is usually 30~35°C, and the pH value is 4.20-4.35. The material of the first-stage crystallizing tank has crystal products, which can be used as the bottom material of the second-stage crystallizing tank. When the first-stage crystallization tank reaches a certain liquid level, it overflows to the secondary crystallization tank. The material is from the first-stage crystallization tank to the second-stage crystallization tank in two ways: First, overflow, overflow from the upper end of the first-stage crystallization tank The mouth is discharged and added to the secondary crystallization tank; the second is to pump the material into the secondary crystallization tank from the bottom of the first-stage crystallization tank by the pump. However, when the pump is discharged, the impeller of the pump may break the larger crystal, so The discharge method is mainly based on overflow, so that not only It can avoid the situation that the impeller of the pump will break up the large crystal when the pump is discharged, and can maintain a certain liquid level height, which is beneficial to adjust the pH value. However, in order to prevent the occurrence of crystal precipitation at the bottom of the crystallizing tank, it is necessary to use a pump to pump the secondary crystallizing tank from the bottom of the tank every few hours, for example every 4 or 5 hours. The crystal cultivation is carried out in a batch mode in a secondary crystallization tank, so that small crystals gradually grow in the tank. In this step, a plurality of crystallizing tanks are used to alternately operate in batches. For example, three tanks of A, B, and C can be used to perform batch crystallization operations in turn. 2/3 of the material in each secondary crystallization tank is from the primary crystallization tank, with this portion as the base; the remaining 1/3 is the concentrate from the concentration step (2) added by flow addition. The batch crystallization operation is started after the predetermined liquid level is reached. Due to the higher concentration of glutamic acid in the concentrate, the addition of 1/3 of the concentrate in a fed-stream manner has the advantages of shortening the addition time, increasing the flow addition efficiency, and reducing the mother liquor at the same glutamic acid content. volume. The flow addition efficiency described herein refers to the mass of pure glutamic acid contained in the concentrate added per unit time. The crystallization operation in the secondary crystallization tank is carried out by a gradient cooling method under stirring, and the temperature and pH in the tank are gradually degraded to form uniform crystals. Typically, the initial temperature in the secondary crystallization tank is about 13 to 18 ° C, the initial pH is about 3.4 to 3.9, the temperature drops by about 2 ° C per hour, the pH drops by about 0.1 per hour, and the final pH is about It is 3.2, the final temperature is about 4 ° C, and the crystallization time is about 10 hours. It takes about 50 hours from the start of the crystallizing tank to the second crystallizing tank. Preferably, the gradient cooling crystallization conditions in the secondary crystallization tank are: an initial temperature of about 15 ° C, an initial pH of about 3.90, a temperature drop of about 2 ° C per hour, and a decrease in pH to about every hour. 0.1, the final pH is about 3.2 and the final temperature is about 4 °C. During the crystallization process, the temperature drop and the decrease of the pH value have a great influence on the crystal form of the crystal. The temperature drop and the decrease of the pH value will form small crystals, crush crystals, and form β crystals easily, and the separation and extraction in the later stage. Caused certain difficulties. Therefore, the temperature and pH should be controlled within the above range and should be as stable as possible. Preferably, in all crystallization operations, i.e., in the operation of a primary or secondary crystallization tank, the maximum temperature fluctuation does not exceed 1 °C of soil, and the maximum fluctuation of pH does not exceed soil 0.1. In the process of the invention, both the primary crystallization tank and the secondary crystallization tank are equipped with agitation means. In order to lower the pH in the crystallizing tank, it is necessary to add a sulfuric acid solution. In order to uniformly mix the materials and sulfuric acid in each crystallizing tank and uniformly distribute the pH value, the present invention uniformly applies sulfuric acid by using a tube-porous porous spraying method, and uses a stirring device to stir the material and sulfuric acid to be more uniform, which is avoided to some extent. The production of β-form crystals provides a more suitable environment for the desired α-form crystals. The agitating device described therein may be a stirring device conventionally used in the art, such as a paddle mixer. After the completion of the secondary crystallizing tank, the obtained crystals can be treated in accordance with a conventional post-treatment method. For example, after the feed liquid is settled in a settling tank, it is centrifuged to separate the mother liquid and crystallize, and the crystal is washed with water to increase the purity and reduce the sulfate content therein, and then dried to obtain the finished glutamic acid. The mother liquor obtained by centrifugation has a wide range of uses and can be comprehensively utilized in various ways. For example, it can be sent to other amino acid production workshops such as glutamic acid, lysine or threonine for efficient use, and can be directly sent to a by-product workshop for processing as a highly efficient compound amino acid fertilizer, or can be directly sold as a fertilizer. As described above, another feature of the method of the present invention is that the unused portions can be discarded for comprehensive utilization in each step, and the comprehensively usable portions include the cells obtained by the step (1) filtration, and the secondary cells obtained after concentration and evaporation. The condensate, and the mother liquor obtained after centrifugation and crystallization. In view of the problems existing in the prior art, the present invention provides a novel extraction method for glutamic acid crystals, which can ensure continuous discharge, easy operation control, can improve particle uniformity of finished glutamic acid, and is low energy. Consumption, low pollution and high returns. The glutamic acid crystal product obtained by the method of the invention has high purity, high yield, small sulfate content in the product (less than 0.3 mg/L), good color perception and uniform crystal grains. The purity of glutamic acid produced by the method of the present invention can reach 98.5% or more by the dry basis content measured by the optical rotation method; the extraction yield, that is, the ratio of the finished glutamic acid actually extracted from the fermentation broth reaches 93% or more. In addition, the bacteria, secondary condensate and mother liquor produced in the production are fully utilized, which not only solves the problem of sewage discharge that has been plaguing the industry, but also turns waste into treasure and creates new economic value. In summary, the beneficial effects of the method of the invention are:

1. The bacteria in the fermentation broth are first removed before isoelectric crystallization, and fine crystals can be avoided.

2. Several secondary crystallizing tanks are connected in parallel. The control method and conditions are the same, and the crystallization operation is carried out in sequence, so that the continuous-intermittent production method of glutamic acid crystallization can be realized. 3. Improve crystallization by a variety of methods:

(1) In the method of the present invention, the pH value in the crystallization tank is lowered, and the sulfuric acid is uniformly added by the tube porous spraying method, and the mixing with the stirring paddle is used to make the mixing of the material and the sulfuric acid more uniform, and the β-type crystallization is avoided to some extent. Produced to provide a more suitable environment for the required alpha crystallization;

(2) The material is mainly used from the first-stage crystallization tank to the second-stage crystallization tank, which can avoid the situation that the impeller of the pump will break the larger crystal when the pump is discharged.

(3) The material 2/3 of the secondary crystallization tank is from the first-stage tank, and the remaining 1/3 is the concentrate after evaporation and evaporation. After the flow reaches the predetermined liquid level, the batch crystallization operation starts, which can shorten the flow. Time, increase the efficiency of the addition, and reduce the volume of the mother liquor.

4. The bacteria obtained by the fermentation broth, the secondary condensate produced by concentrated evaporation, and the mother liquor obtained by centrifugal separation and crystallization are all comprehensively utilized, which not only solves the problem of sewage discharge, but also turns waste into treasure and creates new economic value. . Brief Description of the Drawings Fig. 1 is a schematic view showing the process flow of a method for producing glutamic acid crystals of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

In order to further explain the materials and processes involved in the technical solutions of the present invention, the following examples are given. However, these examples do not limit the scope of the invention in any way. Example 1 Production of glutamic acid crystals from glutamic acid fermentation broth

The production of glutamic acid in this example was carried out in accordance with the process flow shown in Fig. 1.

1, the operation process

(1) glutamic acid fermentation 500m ^3, wherein the glutamic acid content is 14g / 100ml, pH value 7.48. The pH was adjusted to 5.80 with sulfuric acid (concentration 98%) and filtered through an inorganic ceramic membrane. The ceramic membrane used was a K99BW product produced by Oris, France. The filtration conditions were: fermentation temperature 70 ° C, membrane inlet pressure 3 ~3.5kg, outlet pressure 7.0kg. After filtration, a clear fermentation broth and cells were obtained, wherein the supernatant was 487 m ³ . The obtained wet cells are sent to a by-product workshop for drying, and after drying, they are bacterial proteins.

(2) The clarified fermentation broth is concentrated by four-effect evaporation, and the conditions of four-effect evaporation are 90 ° C, 80 ° C, 70 ° C and 60 ° C, respectively, and the concentrated liquid 237 m ^{3 is} evaporated to obtain the concentration of the concentrated liquid. It is 17~22Be ^Q and the secondary condensate is 248m ³ at the same time.

(3) adding the concentrated liquid to the first-stage crystallization tank, the temperature of the first-stage crystallization tank is 30 ° C, and the pH is 4.22. The flow acceleration is 15m ³ /hour.

(4) Set up three secondary crystallizing tanks (secondary crystallizing tanks A, B and C). The feed liquid overflows from the first-stage crystallization tank to the second-stage crystallization tank A. When the feed amount of the second-stage crystallization tank A reaches 2/3 of the total feed amount, the material is stopped from the first-stage crystallization tank, and the flow is added. Concentrate of 1/3 of the total feed volume, flow acceleration 15m ³ / hour; the overflow from the primary crystallization tank begins to overflow to the secondary crystallization tank B, and so on, until the secondary crystallization tank, B And C is all added.

The secondary crystallization tanks A, B, and C are sequentially subjected to crystallization operations under the following conditions: an initial temperature of 15 ° C, an initial pH of 3.90, a temperature drop of 2 每小时 per hour, and a decrease in pH of 0.1 per hour. The final pH was 3.2 and the final temperature was 4 °C. It takes about 50 hours from the start of "priming" in the first-stage crystallizing tank to the end of the secondary crystallizing tank.

In each of the above-mentioned first-stage crystallizing tank and the second-stage crystallizing tank, a paddle stirrer is provided, and at the same time, sulfuric acid is uniformly added by the tube porous spraying method to make the temperature and pH in the crystallizing tank more uniform. Control Within the range given, the temperature and pH fluctuations should be controlled within the following range: Temperature control at ±1 °C and pH control at ±0.1.

(5) The liquid from the secondary crystallization tank is settled in the sedimentation tank, and then enters the centrifuge to separate the mother liquor and crystallize. The crystal is washed with water to collect the crystallized product; the washing water and the mother liquor are combined and sent to the by-product workshop to prepare a composite amino acid fertilizer.

(6) The wet cells are sent to the by-product workshop for drying. The method is spray granulation by a fluidized granulation coating dryer. The equipment is batch production, the temperature is controlled at 160 ° C, and the drying time is 50. minute. -

(7) The secondary condensate produced by evaporation can be directly applied to the fermentation production of amino acids such as lysine, threonine and glutamic acid without any treatment. When the fermentation ingredients need to be added with water, the water can be changed to a secondary condensate, and the secondary condensate can provide a high-efficiency nitrogen source.

(8) The mother liquor obtained by centrifugation is added with corn gluten protein content of 30% in the by-product workshop, and then spray granulated by a fluidized granulation coating dryer at a temperature of 160 ° C and a drying time of 50 minutes. Batch drying, the dried product is a compound amino acid fertilizer.

2, the product

Finished product of glutamic acid: 63 tons, yield of finished product: 93%, dry content of glutamic acid 98.5%;

Bacterial protein (after drying): 4.6 tons, used to make high-efficiency fertilizers; Secondary condensate: 248m ³ , can be used in the fermentation production of amino acids such as lysine, threonine and glutamic acid to provide a high-efficiency nitrogen source for the fermentation process;

Mother liquor: 250m ³ , adding 45.5 tons of compound amino acid fertilizer to corn protein with corn syrup protein content of 30% in the by-product workshop. The embodiments of the present invention have been described in detail above, and it is obvious to those skilled in the art that many modifications and changes can be made without departing from the spirit of the invention. All such variations and modifications are within the scope of the invention.

Claims

The claims are:

A method for producing glutamic acid crystals by extracting glutamic acid by intermittent-continuous isoelectric crystallization of a glutamic acid fermentation broth, which is characterized in that the bacteria in the fermentation broth are first removed before isoelectric crystallization.

2. The method of claim 1 comprising the steps of:

(4) The crystal particles obtained in the previous step are sedimented by a sedimentation tank, centrifuged, washed, and dried to obtain glutamic acid crystals.

3. A method according to claim 2, wherein in said crystallization operation, 2/3 of the total amount of feed in the secondary crystallization tank is overflowed from the primary crystallization tank, and the remaining 1/3 is the step 2 obtained glutamic acid concentrate.

The method according to claim 2, wherein the pH of the glutamic acid fermentation broth is first adjusted to 5.5-6.0, preferably the pH is adjusted to pH = 5.8, before the glutamic acid fermentation broth is filtered.

5. The method according to claim 2, wherein the filtering step of the glutamic acid fermentation liquid can be filtered by using an inorganic ceramic membrane or an ultrafiltration membrane to remove impurities such as remaining bacteria or proteins, preferably using an inorganic ceramic membrane, which is shut off. The molecular weight is 300KD.

The method according to claim 2, wherein the evaporation concentration of the glutamic acid fermentation liquid is preferably carried out by a four-effect evaporation method, and the concentration of the concentrated glutamic acid concentrate reaches 13 to 22 Be°, preferably the glutamic acid concentrate. The concentration reaches 17~22Be°.

7. The method according to claim 2, wherein the temperature in the first stage crystallizing tank is 30 to 35 ° C, and the pH is 4.20 to 4.35.

8. The method of claim 2 wherein the secondary crystallization tank is operated intermittently and the crystallization method is carried out by gradient cooling crystallization.

9. The method according to claim 8, wherein the gradient temperature crystallization method is carried out under stirring, the initial temperature is 13 to 18 ° C, the initial pH is 3.4 to 3.9, and the temperature is lowered to about 2 V per hour. The pH is reduced by about 0.1 per hour, the final pH is about 3.2, and the final temperature is about 4. C; The preferred gradient cooling crystallization conditions are: The starting temperature of the secondary crystallization tank is about 15 ° C, the initial pH is about 3.90, the temperature is lowered by 2 ° C per hour, and the pH is lowered to 0.1 per hour. The final pH is about 3.2 and the final temperature is about 4 Torr. More preferably, the maximum temperature fluctuation during the crystallization operation does not exceed 1 ° C of the soil, and the maximum fluctuation of the pH does not exceed ± 0.1.

10. The method according to claim 2, wherein the first-stage crystallization tank and the second-stage crystallization tank are each subjected to a porous pipe spray method to add an aqueous sulfuric acid solution for adjusting the pH value; in the first-stage crystallization tank and the: The secondary crystallization tank is also equipped with a stirring device, and the preferred stirring device is a paddle stirrer.

1 1. A method according to any of claims 1-10, the method comprising the steps of:

(1) After sterilizing the glutamic acid fermentation broth, the pH is adjusted to pH=5.8, and then the cells are removed by filtration through an inorganic ceramic membrane to obtain a clarified glutamic acid fermentation liquid, wherein the inorganic ceramic membrane has a molecular weight cut off. 300KD;

(2) The glutamic acid fermentation broth is concentrated by a multi-effect evaporation method to obtain a glutamic acid concentrate, and the concentrated concentration reaches 17 to 22 Be. ;

(3) crystallization of the glutamic acid concentrate in a primary crystallizing tank and a plurality of secondary crystallizing tanks, first adding the obtained glutamic acid concentrate to a primary crystallizing tank for crystallization, primary crystallization The temperature in the tank is 30-35 ° C, and the pH is 4.20-4.35;

The glutamic acid-containing stream is then continuously overflowed from the primary crystallization tank to the secondary crystallization tank, and the gradient crystallization is carried out in a secondary crystallization tank. The crystallization operation is carried out under stirring, and the gradient cooling crystallization conditions are: The initial temperature is about 15 ° C, the initial pH is about 3.90, the temperature drop is 2 ° C per hour, the pH is reduced to 0.1 per hour, and the final pH is about 3.2. The final temperature is about 4 ° C _;

Wherein 2/3 of the total feed amount in the secondary crystallization tank overflows from the first-stage crystallization tank, and the remaining 1/3 is the glutamic acid concentrate obtained in the step 2;

12. The method according to claim 11, wherein the maximum fluctuation in temperature during said crystallization operation does not exceed 1 °C of soil, and the maximum fluctuation of pH does not exceed ±0.1.

The method according to claim 2, wherein the filtered bacterial cells, the secondary condensation by evaporation to produce a secondary condensate, and the mother liquor obtained by centrifuging the glutamic acid crystals are used in combination.

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