Method for improving yield of glutamic acid by using annular process formed by glutamic acid isoelectric mother liquor

Abstract

The invention discloses a method for improving the yield of glutamic acid by using an annular process formed by glutamic acid isoelectric mother liquor, and belongs to the technical field of industrial fermentation. The method comprises the following steps: carrying out membrane treatment, two-stage electrodialysis treatment, acid hydrolysis treatment, acid decoloration treatment and other technical means on the glutamic acid isoelectric mother liquor, and finally recycling the obtained hydrolysis decoloration solution to replace sulfuric acid to adjust the isoelectric crystallization operation of the fermentation liquor, thereby constructing an annular process. In the whole annular process, pyroglutamic acid in the isoelectric mother liquor is hydrolyzed into glutamic acid through acid hydrolysis, and the pyroglutamic acid and the glutamic acid in the isoelectric mother liquor are recycled and reused in the operation process of glutamic acid isoelectric crystallization, so that the yield of the glutamic acid is increased; simultaneously generated concentrated solution and concentrated water are respectively filtered by a plate frame, concentrated and dried to obtain mycoprotein and ammonium sulfate. By means of the treatment method, the yield of glutamic acid is increased, the yield of mycoprotein and the yield of ammonium sulfate are increased, and huge economic benefits and environmental benefits are achieved.

Description

Technical Field

[0001] The invention relates to a method for improving the yield of glutamic acid by utilizing glutamic acid isoelectric mother liquor to form a ring process, and belongs to the technical field of industrial fermentation. Background Art

[0002] At present, domestic glutamic acid products are mainly produced by microbial fermentation. After fermentation, the concentration of glutamic acid in the fermentation broth reaches 170-200 g / L. To extract glutamic acid from the fermentation broth, the current industry mainly adopts the "concentrated isoelectric extraction process" (see: Guo Ming, Ren Fang, etc. Concentrated high-temperature continuous isoelectric crystallization process for glutamic acid extraction. Fermentation Science and Technology Newsletter, 2009, 38 (1): 42-43). The extraction yield of this process is generally between 85% and 88%. The mother liquor produced after glutamic acid extraction is called isoelectric mother liquor. The isoelectric mother liquor contains not only bacterial cells, ammonium sulfate (about 70-120 g / L) and 20-35 g / L of glutamic acid, but also some high-value soluble proteins, miscellaneous amino acids, residual sugars and other beneficial components. Due to the presence of impurities such as bacteria and ammonium sulfate, some high-value components in the isoelectric mother liquor, such as glutamic acid, soluble protein, and miscellaneous amino acids, cannot be directly recovered, and the presence of high concentrations of ammonium sulfate makes it impossible to carry out biochemical treatment of the isoelectric mother liquor. Considering my country's annual production of more than 3 million tons of glutamic acid, the low-level treatment of the isoelectric mother liquor not only makes a large number of high-value products unable to be recovered, causing significant economic losses, but also causes great damage to the environment.

[0003] At present, the most commonly used method for treating isoelectric mother liquor is to use concentration and spray drying to turn the mother liquor into fertilizer to reduce the pollution of isoelectric mother liquor to the environment. However, the large amount of waste gas generated in the process of fertilizer production, the low fertilizer efficiency caused by high temperature, the poor solubility of fertilizer and other factors have restricted the production and sale of fertilizers. At the same time, the low yield of glutamic acid extraction, the high operating cost of isoelectric mother liquor fertilizer production, and the existence of waste gas pollution have led to the reduction of the benefits of monosodium glutamate production enterprises, affecting the healthy development of monosodium glutamate production enterprises.

[0004] In the prior art, patent CN 110407388 A (a resource treatment method for waste liquid from electro-extraction such as glutamate concentration) discloses a resource treatment method for waste liquid from electro-extraction such as glutamate concentration, wherein the waste liquid from electro-extraction such as glutamate concentration is first treated with an ultrafiltration membrane to obtain a membrane concentrate and a membrane filtrate, wherein the membrane concentrate is filtered and dried to obtain bacterial protein, and the membrane filtrate is decolorized with activated carbon and then subjected to electrodialysis treatment to obtain an electrodialysis retentate and an electrodialysis permeate, wherein the electrodialysis retentate and the electrodialysis permeate are respectively subjected to evaporation concentration, cooling crystallization, and separation and recovery to obtain glutamic acid and ammonium sulfate. However, this method does not achieve the separation and treatment of pyroglutamic acid, and there is still room for improvement in resource utilization, and the recovered glutamic acid has a problem of low purity.

[0005] Patent CN 116803978 A (Method for recovering pyroglutamic acid from glutamic acid fermentation broth) discloses a method for recovering pyroglutamic acid from glutamic acid fermentation broth, comprising removing bacterial cells from glutamic acid fermentation broth by centrifugation, extracting glutamic acid by isoelectric separation after concentrating the supernatant, separating ammonium sulfate from glutamic acid isoelectric mother liquor by concentrating and crystallizing, separating ammonium sulfate from secondary mother liquor by electrodialysis after decolorization and filtration, collecting concentrated water and fresh water respectively, recycling fresh water to isoelectric separation process, and separating ammonium sulfate and pyroglutamic acid by alcohol extraction and filtration. However, the fresh water contains not only glutamic acid, but also a large amount of solids such as other heteroamino acids, residual sugar, residual dextrin and pigment. Direct recycling not only affects the purity of glutamic acid, and further affects the refining effect of glutamic acid, but also increases the total solid concentration in the isoelectric crystallization tank due to the recycling of a large amount of solids, which affects the yield of glutamic acid. At the same time, the continuous recycling of fresh water will eventually lead to the failure of isoelectric crystallization due to excessive accumulation of non-ionizable solids, and the implementation of the process cannot be truly realized. In addition, there are ammonium sulfate, pyroglutamic acid and glutamic acid in the concentrated water. Anhydrous ethanol can be used to separate ammonium sulfate, but both glutamic acid and pyroglutamic acid are insoluble in anhydrous ethanol. The obtained pyroglutamic acid is still a mixture and still needs to be further separated in depth, otherwise its true value cannot be realized. In addition, in the process of using ethanol to recover pyroglutamic acid, the characteristics of ethanol not only improve the safety level of the plant, but the loss of ethanol also increases its economic investment, so it is necessary to analyze its economic feasibility in more depth.

[0006] Therefore, it is necessary to continue to find a method for recovering glutamate and other high-value products from glutamate and other electrolyte mother liquors, and to effectively separate and use various substances in glutamate and other electrolyte mother liquors to maximize resource utilization while ensuring that costs are not significantly increased. Summary of the invention

[0007] Technical issues

[0008] The existing treatment methods of glutamic acid isoelectric mother liquor have the problems of high treatment cost, failure to extract other high-value products, recycling of pyroglutamic acid and glutamic acid, and environmental pollution caused by waste gas, which makes the treatment of isoelectric mother liquor a burden for the healthy operation of the monosodium glutamate industry. The existing technology still has the problems of low resource utilization and low purity of the recovered glutamic acid.

[0009] Technical Solution

[0010] In order to solve the above problems, the present invention provides a method for treating glutamic acid isoelectric mother liquor by using membrane separation, thermal denaturation, evaporation crystallization, multi-stage electrodialysis, acid hydrolysis, acid decolorization treatment and other technologies, so as to achieve the recovery of more glutamic acid, bacterial protein and ammonium sulfate from the isoelectric mother liquor; the pyroglutamic acid in the isoelectric mother liquor is hydrolyzed into glutamic acid, and the hydrolyzed glutamic acid is recycled and reused in the isoelectric crystallization process to replace the use of sulfuric acid, thereby forming a circular production process to improve the yield of glutamic acid; the condensed water generated in the evaporation process can be recycled and reused in the production of monosodium glutamate. The method of the present invention not only obtains more glutamic acid, bacterial protein and ammonium sulfate, but also realizes the reuse of glutamic acid in the isoelectric mother liquor, improves the glutamic acid extraction rate, eliminates the pollution of the environment by high-concentration isoelectric mother liquor and waste gas, and reduces the consumption of water resources due to the recycling of evaporated condensed water, so as to achieve not only considerable economic benefits but also good environmental benefits.

[0011] Specifically, the technical solution of the present invention is: a method for improving the yield of glutamic acid by forming a ring process using glutamic acid isoelectric mother liquor, the method comprising:

[0012] The glutamic acid isoelectric mother liquor is first treated with a ceramic membrane to obtain a ceramic membrane clear solution and a ceramic membrane concentrated solution; the ceramic membrane concentrated solution is subjected to heat denaturation and then filtered to obtain bacterial protein and filtered clear solution, and the filtered clear solution is returned to the ceramic membrane for treatment; the ceramic membrane clear solution is treated with an ultrafiltration membrane to obtain an ultrafiltration concentrate and an ultrafiltration clear solution, and the ultrafiltration concentrate is returned for heat denaturation and filtration; the ultrafiltration clear solution is subjected to primary electrodialysis treatment to obtain primary concentrated water and primary fresh water; the primary concentrated water is subjected to reduced pressure concentration, evaporation crystallization and solid-liquid separation to obtain ammonium sulfate crystals, and the separated filtrate is returned to the primary electrodialysis treatment; the primary fresh water is subjected to secondary electrodialysis after the pH is adjusted to obtain secondary concentrated water and secondary fresh water; the secondary concentrated water is subjected to reduced pressure concentration, cooling crystallization and solid-liquid separation to obtain glutamic acid crystals, and the filtrate obtained by solid-liquid separation is circulated back to the secondary fresh water; the secondary fresh water is subjected to acid hydrolysis after reduced pressure concentration, and then filtered and decolorized to obtain a hydrolyzed decolorized solution; the hydrolyzed decolorized solution is used for regulating the isoelectricity of the glutamic acid fermentation liquid, and glutamic acid can be separated again.

[0013] Furthermore, the ceramic membrane treatment is to remove the bacteria and macromolecular proteins in the isoelectric mother liquor to facilitate subsequent separation and purification operations; the ceramic membrane used in the ceramic membrane treatment has a pore size of 10-50nm, an operating pressure of 0.2-0.6MPa, an operating temperature of 35-60°C, a membrane surface flow rate of 3-6m / s, and an outlet turbidity of ≤0.1NTU.

[0014] Furthermore, the thermal denaturation is to denature the bacterial protein in the concentrated solution by heating so as to facilitate subsequent separation; the thermal denaturation is: heating the ceramic membrane concentrated solution to 60-90°C for 10-50 minutes; the heat source for heating can be steam.

[0015] Furthermore, sodium polyacrylate may be added to the thermal denaturation; the added amount of sodium polyacrylate is 300 to 600 ppm.

[0016] Furthermore, the filtering may be selected as plate-and-frame filtering, that is, filtering is performed using plate-and-frame filtering.

[0017] Furthermore, in the ultrafiltration membrane treatment, the molecular weight cut-off is 5 to 500 kDa, the operating pressure is 0.1 to 0.6 MPa, the operating temperature is 25 to 60° C., and the membrane surface flow rate is 2 to 4 m / s.

[0018] Furthermore, the parameters of the primary electrodialysis treatment are: the membrane voltage is maintained at 0.7-0.9V, the operating temperature is 20-35°C, and the electrodialysis is stopped when the conductivity of the primary fresh water is 10-20mS / cm.

[0019] Furthermore, the reduced pressure concentration of the primary concentrated water is carried out by using a multi-effect falling film evaporator or a rising film evaporator.

[0020] Preferably, the reduced-pressure concentration of the primary concentrated water is carried out using a multi-effect falling film evaporator; the multi-effect falling film evaporator is a four-effect falling film evaporator.

[0021] Furthermore, the concentration multiple of the primary concentrated water under reduced pressure is between 10 and 20 times.

[0022] Specifically, the reduced pressure concentration of the primary concentrated water is carried out by a four-effect falling film evaporator, the evaporation temperature of the first effect is controlled at 100-120°C, the evaporation temperature of the last effect is controlled at 45-60°C, the vacuum degree of the last effect is controlled at 10-20 kPa, and the evaporation concentration is 10-20 times.

[0023] Furthermore, the evaporation and crystallization temperature of the primary concentrated water is 40-60°C.

[0024] Furthermore, the solid-liquid separation of the primary concentrated water can be carried out using a cone blue centrifuge or a scraper centrifuge; the temperature during centrifugation is controlled at 20-60°C.

[0025] Furthermore, the pH of the primary fresh water is adjusted to 4.5-7.0.

[0026] Preferably, the pH of the primary fresh water is adjusted to 5.0-6.0.

[0027] Furthermore, the parameters of the secondary electrodialysis treatment are: the membrane voltage is maintained at 0.7-0.9V, the operating temperature is 20-35°C, and the electrodialysis is stopped when the conductivity of the secondary fresh water is 2-5mS / cm.

[0028] Furthermore, the pH of the secondary concentrated water is adjusted to 3-4.

[0029] Furthermore, the reduced pressure concentration of the secondary concentrated water is: firstly concentrated by multi-effect reduced pressure evaporation, and then concentrated by single-effect negative pressure evaporation or double-effect reduced pressure evaporation.

[0030] Specifically, the vacuum concentration of the secondary concentrated water can be as follows: firstly, four-effect vacuum concentration is adopted to control the first-effect evaporation temperature to 85-90°C, the second-effect evaporation temperature to 45-60°C, the second-effect vacuum degree to 10-20kPa, and the concentration is 2-5 times; then, single-effect negative pressure evaporation is adopted to control the evaporation temperature to 45-60°C, the single-effect evaporation absolute pressure to 10-20kPa, and the evaporation concentration is 5-10 times.

[0031] Furthermore, the cooling crystallization of the secondary concentrated water is as follows: cooling to 10-35°C at a cooling rate of 1-3°C / h.

[0032] Furthermore, solid-liquid separation of the secondary concentrated water can be performed using a cone blue centrifuge or a scraper centrifuge.

[0033] Furthermore, the reduced pressure concentration of the secondary fresh water is carried out using a multi-effect falling film evaporator or a rising film evaporator.

[0034] Specifically, the reduced pressure concentration of the secondary fresh water is carried out by a multi-effect falling film evaporator, the evaporation temperature of the first effect is controlled at 90-105°C, the evaporation temperature of the last effect is controlled at 45-60°C, the vacuum degree of the last effect is controlled at 10-20 kPa, and the concentration is stopped when the solid concentration is 50-65%.

[0035] Furthermore, the acid hydrolysis of the secondary fresh water is carried out using concentrated sulfuric acid; the concentration of the concentrated sulfuric acid is 95-98wt%, and the amount of concentrated sulfuric acid added is 30-50% of the volume of the secondary fresh water concentrated under reduced pressure; the temperature of the acid hydrolysis is 120-150°C, and the hydrolysis time is 1-3 hours.

[0036] Furthermore, the secondary fresh water is filtered by plate and frame filtration.

[0037] Furthermore, the decolorization is activated carbon decolorization or membrane decolorization.

[0038] Furthermore, when activated carbon is used for decolorization, the added mass (g) of the activated carbon is 1 to 3% of the volume (mL) of the hydrolyzate obtained after filtration.

[0039] In the above method, the filtrate is repeatedly processed and utilized, thereby increasing the ammonium sulfate yield, and the obtained ammonium sulfate product can be sold as fertilizer. In addition, the process adopts primary electrodialysis to separate the strong electrolyte ammonium sulfate from the weak electrolyte glutamic acid and pyroglutamic acid by regulating the conductivity of the feed solution. The primary fresh water contains a large amount of glutamic acid and unusable pyroglutamic acid, as well as a certain amount of miscellaneous amino acids and some small molecular proteins, residual sugars, etc. Secondary electrodialysis is then used to separate the weak electrolyte from the non-ionizable substances by regulating the pH and conductivity of the feed solution, so that glutamic acid and pyroglutamic acid are concentrated in the secondary concentrated water, and small molecular proteins, residual sugars and other organic matter are concentrated in the secondary fresh water. The different properties of glutamic acid and pyroglutamic acid are then used to separate them. The organic matter and pyroglutamic acid are finally hydrolyzed into humus and glutamic acid into glutamic acid by acid hydrolysis. The humus produced can be sold as fertilizer, and the glutamic acid produced is recycled to the isoelectric process. After the pigment is removed, the hydrolyzate can be circulated back to the isoelectric tank instead of sulfuric acid to adjust the isoelectric process, thereby achieving the purpose of increasing the yield of glutamic acid.

[0040] Beneficial effects achieved by the present invention:

[0041] 1. The present invention can recycle more than 98% of bacterial protein and more than 85% of ammonium sulfate in the isoelectric mother liquor, increase the yield of ammonium sulfate by 450kg per ton of monosodium glutamate, and achieve a total glutamic acid yield of more than 95%, thereby increasing the economic benefit of each ton of monosodium glutamate by more than RMB 700.

[0042] 2. The present invention adopts secondary electrodialysis, and separates glutamic acid, pyroglutamic acid and organic matter by regulating the pH and conductivity of the feed solution, so as to utilize the different properties of glutamic acid and pyroglutamic acid for separation, and the glutamic acid obtained by separation and collection has higher purity. At the same time, the pyroglutamic acid can also be hydrolyzed subsequently and the hydrolyzate can be recycled and reused in isoelectric crystallization, thus constructing a ring production process to achieve an increase in the total yield of glutamic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The present invention is a schematic diagram of the overall process of a method for producing feed using glutamic acid isoelectric mother liquid. DETAILED DESCRIPTION

[0044] Detection Methods

[0045] Glutamic acid content determination method: The biosensor SBA-40 was used for determination.

[0046] Determination method of ammonium sulfate content: Determination is carried out in accordance with the national standard GB / T 535-2020.

[0047] Solid content determination method: Abbe refractometer was used for determination.

[0048] Calculation method of glutamic acid purity: Glutamic acid purity % = {(C 1 ×V 1 )÷G 1}×100%, where C 1 To detect the concentration of glutamate (g / L), V 1 is the volume of the test sample (L); G 1 Weigh the solid weight of the test sample (g).

[0049] Instrument use

[0050] The four-effect reduced pressure concentration is carried out by a four-effect falling film evaporation system, which was purchased from some companies of Shanghai Shennong Energy Saving and Environmental Protection Technology Co., Ltd., model FM-4; the plate and frame filtration is carried out by a plate and frame filter, which was purchased from Haining Yongsheng Membrane Filtration Equipment Manufacturing Co., Ltd., model YSW150-10; the electrodialysis treatment system is purchased from Shandong Tianwei Membrane Technology Co., Ltd., model TWED-2-20.

[0051] The present invention will be combined with Figure 1 , further described in the form of embodiments:

[0052] Example 1

[0053] (1) Take 5000mL of glutamic acid isoelectric mother liquor (glutamic acid concentration is 26g / L, ammonium sulfate is 90g / L) and treat it through a 20nm ceramic membrane. The operating pressure is 0.4MPa, the operating temperature is 45℃, and the membrane surface flow rate is controlled at 5m / s to obtain 4610mL of ceramic membrane clear liquid and 390mL of ceramic membrane concentrated liquid. The turbidity of the ceramic membrane clear liquid is 0.005NTU.

[0054] (2) The ceramic membrane concentrate in step (1) was heated to 85° C., sodium polyacrylate (PAAS) was added at a concentration of 450 ppm and mixed, maintained for 30 min, and then filtered through a plate and frame filter to obtain 246 mL of filtrate and 142 g of filter cake. The filtrate was recycled back to step (1) to obtain a ceramic membrane clear liquid, and the filter cake was dried to obtain 74.8 g of dry bacterial protein.

[0055] (3) The ceramic membrane clear solution obtained by mixing step (1) and step (2) totals 4836 mL, wherein the concentration of glutamic acid is 26 g / L and the concentration of ammonium sulfate is 90 g / L.

[0056] (4) The ceramic membrane clear liquid obtained in step (3) is treated with an ultrafiltration membrane with a molecular weight cutoff of 300 kDa, and the operating temperature is controlled to be 25° C., the operating pressure is 0.15 MPa, and the membrane surface flow rate is 2 m / s to obtain membrane filtrate and membrane concentrate. The obtained membrane concentrate is returned to step (1) for treatment, and then the obtained ceramic membrane clear liquid is taken and returned to the ultrafiltration membrane for treatment to obtain membrane filtrate. A total of 4810 mL of membrane filtrate is obtained by two ultrafiltrations.

[0057] (5) The membrane filtrate produced in step (4) enters the electrodialysis treatment system and is treated under the conditions of an operating voltage of 0.9 V for each pair of membranes and a temperature of 25° C. The operation is stopped when the conductivity of the primary fresh water drops to 18 mS / cm, and 7200 mL of primary concentrated water and 2600 mL of primary fresh water are obtained respectively. The glutamate concentration in the primary fresh water is 44.3 g / L.

[0058] (6) The primary concentrated water produced in step (5) is concentrated by four-effect vacuum, the evaporation temperature of the first effect is controlled to be 115° C., the evaporation temperature of the last effect is controlled to be 58° C., the vacuum degree of the last effect is controlled to be 18 kPa, and the evaporation concentration is 14 times, and finally cooled to 40° C. The cooled concentrated liquid is separated, and the separated filtrate is returned to step (5) for treatment. The separated solid is ammonium sulfate crystals, totaling 399 g, with a recovery rate of 88.7%.

[0059] (7) The pH value of the primary fresh water produced in step (5) is controlled at 6.0, and the fresh water enters the secondary electrodialysis treatment, and the treatment is carried out under the conditions of an operating voltage of 0.75 V for each pair of membranes and a temperature of 25° C. When the conductivity of the secondary fresh water drops to 4000 μs / cm, the operation is stopped, and 2500 mL of secondary concentrated water and 2400 mL of secondary fresh water are obtained respectively.

[0060] (8) The pH value of the secondary concentrated water produced in step (7) is adjusted to 3.2, and four-effect vacuum concentration is adopted, the first-effect evaporation temperature is controlled to 88° C., the second-effect evaporation temperature is controlled to 52° C., the second-effect vacuum degree is controlled to 14 kPa, and the concentration is 3 times; then single-effect negative pressure evaporation is adopted, the evaporation temperature is controlled to 52° C., the single-effect evaporation absolute pressure is controlled to 14 kPa, and the evaporation concentration is 8 times.

[0061] (9) The concentrated liquid produced in step (8) is cooled and crystallized, and the cooling rate is controlled to be 1.0° C. / h. It is finally cooled to 12° C. and separated by a three-legged centrifuge. The liquid obtained by centrifugation is returned to step (7) and combined with the secondary fresh water. The solid obtained by centrifugation is glutamic acid crystals, totaling 117.4 g. The recovery rate of glutamic acid is 76.1%, and the purity is 84.2%.

[0062] (10) The secondary fresh water produced in step (7) is concentrated by four-effect vacuum concentration, with the first-effect evaporation temperature controlled at 95° C., the second-effect evaporation temperature controlled at 58° C., the second-effect vacuum degree controlled at 18 kPa, and the concentration is stopped when the solid concentration reaches 62%.

[0063] (11) adding concentrated sulfuric acid to the concentrated solution produced in step (10) for hydrolysis, wherein the concentrated sulfuric acid concentration is 98 wt %, the amount added is 35% of the volume of the concentrated solution, the hydrolysis temperature is 130° C., and the hydrolysis time is 2 hours; after the hydrolysis is completed, the hydrolyzate and humus are obtained by plate and frame filtration.

[0064] (12) Add activated carbon to the hydrolyzate produced in step (11) in an amount of 2% (m / v) of the volume of the hydrolyzate, mix well, decolorize at 80° C. for 60 min, and then filter through a plate and frame to obtain a hydrolyzed decolorized solution.

[0065] (13) 5000 mL of concentrated fermentation broth, wherein the glutamic acid concentration is 360 g / L, is taken and the fermentation broth is subjected to an isoelectric process using the hydrolysis decolorization solution produced in step (12); then 1654.2 g of glutamic acid is separated to obtain 6500 mL of isoelectric mother liquor, wherein the glutamic acid concentration in the mother liquor is 28 g / L, and the total yield of glutamic acid is 97.4%.

[0066] Example 2

[0067] (1) Take 4000mL of glutamic acid isoelectric mother liquor (glutamic acid concentration is 25g / L, ammonium sulfate is 86g / L) and treat it through a 30nm ceramic membrane. The operating pressure is 0.3MPa, the operating temperature is 40℃, and the membrane surface flow rate is controlled at 4m / s to obtain 3630mL of ceramic membrane clear liquid and 370mL of ceramic membrane concentrated liquid. The turbidity of the ceramic membrane clear liquid is 0.05NTU.

[0068] (2) The ceramic membrane concentrate in step (1) was heated to 80°C, and sodium polyacrylate (PAAS) was added at a concentration of 450 ppm and mixed, maintained for 40 minutes, and then filtered through a plate and frame filter to obtain 260 mL of filtrate and 105 g of filter cake. The filtrate was recycled to step (1) to obtain a ceramic membrane clear liquid, and the filter cake was dried to obtain 56.2 g of dry bacterial protein.

[0069] (3) The ceramic membrane clear solution of step (1) and step (2) is mixed to a total of 3890 mL, wherein the concentration of glutamic acid is 25 g / L and the concentration of ammonium sulfate is 86 g / L.

[0070] (4) The ceramic membrane clear liquid obtained in step (3) is treated with an ultrafiltration membrane with a molecular weight cutoff of 50 kDa, and the operating temperature is controlled to be 35° C., the operating pressure is 0.25 MPa, and the membrane surface flow rate is 3 m / s to obtain membrane filtrate and membrane concentrate. The obtained membrane concentrate is returned to step (1) for treatment, and then the obtained ceramic membrane clear liquid is taken and returned to the ultrafiltration membrane for treatment to obtain membrane filtrate. A total of 3830 mL of membrane filtrate is obtained by two ultrafiltrations.

[0071] (5) The membrane filtrate produced in step (4) enters the electrodialysis treatment system and is treated under the conditions of an operating voltage of 0.8 V for each pair of membranes and a temperature of 30° C. The operation is stopped when the conductivity of the primary fresh water drops to 15 mS / cm, and 5650 mL of primary concentrated water and 2150 mL of primary fresh water are obtained respectively. The glutamate concentration in the primary fresh water is 40.1 g / L.

[0072] (6) The primary concentrated water produced in step (5) is concentrated by four-effect vacuum, the evaporation temperature of the first effect is controlled to be 110° C., the evaporation temperature of the last effect is controlled to be 58° C., the vacuum degree of the last effect is controlled to be 18 kPa, and the evaporation concentration is 15.5 times. Finally, the concentrated liquid is cooled to 35° C. and the cooled concentrated liquid is separated. The filtrate obtained by separation is returned to step (5) for treatment. The solid obtained by separation is ammonium sulfate crystals, totaling 305.6 g, with a recovery rate of 88.8%.

[0073] (7) The pH value of the primary fresh water produced in step (5) is controlled at 5.5, and the fresh water enters the secondary electrodialysis treatment, and the treatment is carried out under the conditions of an operating voltage of 0.8 V for each pair of membranes and a temperature of 25° C. When the conductivity of the secondary fresh water drops to 3000 μs / cm, the operation is stopped, and 2080 mL of secondary concentrated water and 2000 mL of secondary fresh water are obtained respectively.

[0074] (8) The pH value of the secondary concentrated water produced in step (7) is adjusted to 3.2, and four-effect vacuum concentration is adopted, the first-effect evaporation temperature is controlled at 88° C., the second-effect evaporation temperature is 52° C., the second-effect vacuum degree is 14 kPa, and the concentration is 2.5 times; then single-effect negative pressure evaporation is adopted, the evaporation temperature is controlled at 52° C., the single-effect evaporation absolute pressure is 14 kPa, and the evaporation concentration is 7 times.

[0075] (9) The concentrated liquid produced in step (8) is cooled and crystallized, and the cooling rate is controlled to be 1.5° C. / h. It is finally cooled to 20° C. and separated by a three-legged centrifuge. The liquid obtained by centrifugation is returned to step (7) and combined with the secondary fresh water. The solid obtained by centrifugation is glutamic acid crystals, totaling 75.5 g. The recovery rate of glutamic acid is 65.5%, and the purity is 86.8%.

[0076] (10) The pH value of the secondary fresh water produced in step (7) is controlled at about 5.5, and four-effect vacuum concentration is adopted, with the first-effect evaporation temperature being controlled at 90° C., the second-effect evaporation temperature being controlled at 56° C., and the second-effect vacuum degree being controlled at 16 kPa. Concentration is stopped when the solid concentration reaches 58%.

[0077] (11) adding concentrated sulfuric acid to the concentrated solution produced in step (10) for hydrolysis, wherein the concentration of the concentrated sulfuric acid is 98 wt %, the amount added is 40% of the volume of the concentrated solution, the hydrolysis temperature is 140° C., and the hydrolysis time is 2.5 hours; after the hydrolysis is completed, the hydrolyzate and humus are obtained by plate and frame filtration.

[0078] (12) Add activated carbon to the hydrolyzate produced in step (11) in an amount of 2.5% (m / v) of the volume of the hydrolyzate, mix well, decolorize at 70° C. for 70 min, and then filter through a plate and frame to obtain a hydrolyzed decolorized solution.

[0079] (13) 4000 mL of concentrated fermentation broth, wherein the glutamic acid concentration is 350 g / L, is taken and the fermentation broth is subjected to an isoelectric process using the hydrolysis decolorization solution produced in step (12); then 1304.6 g of glutamic acid is separated to obtain 5500 mL of isoelectric mother liquor, wherein the glutamic acid concentration in the mother liquor is 24 g / L, and the total yield of glutamic acid is calculated to be 95.1%.

[0080] Example 3

[0081] (1) Take 6000mL of glutamic acid isoelectric mother liquor (glutamic acid concentration is 23g / L, ammonium sulfate is 85g / L) and treat it through a 20nm ceramic membrane. The operating pressure is 0.5MPa, the operating temperature is 50℃, and the membrane surface flow rate is controlled at 5m / s to obtain 5520mL of ceramic membrane clear liquid and 480mL of ceramic membrane concentrated liquid. The turbidity of the ceramic membrane clear liquid is 0.02NTU.

[0082] (2) The ceramic membrane concentrate in step (1) was heated to 70°C, and sodium polyacrylate (PAAS) was added at a concentration of 420 ppm and mixed, maintained for 50 minutes, and then filtered by plate and frame pressure to obtain 290 mL of filtrate and 180 g of filter cake. The filtrate was recycled to step (1) to obtain a ceramic membrane clear liquid, and the filter cake was dried to obtain 88.5 g of dry bacterial protein.

[0083] (3) The ceramic membrane clear solution of step (1) and step (2) is mixed to a total of 5800 mL, wherein the concentration of glutamic acid is 23 g / L and the concentration of ammonium sulfate is 85 g / L.

[0084] (4) The ceramic membrane clear liquid obtained in step (3) is treated with an ultrafiltration membrane with a molecular weight cutoff of 5 kDa, and the operating temperature is controlled to be 30°C, the operating pressure is 0.35 MPa, and the membrane surface flow rate is 4 m / s to obtain membrane filtrate and membrane concentrate. The obtained membrane concentrate is returned to step (1) for treatment, and then the obtained ceramic membrane clear liquid is taken and returned to the ultrafiltration membrane for treatment to obtain membrane filtrate. A total of 5650 mL of membrane filtrate is obtained by two ultrafiltrations.

[0085] (5) The membrane filtrate produced in step (4) enters the electrodialysis treatment system and is treated under the conditions of an operating voltage of 0.7 V for each pair of membranes and a temperature of 25° C. The operation is stopped when the conductivity of the primary fresh water drops to 12 mS / cm, and 8250 mL of primary concentrated water and 3050 mL of primary fresh water are obtained, respectively. The glutamate concentration in the primary fresh water is 38.3 g / L.

[0086] (6) The concentrated water produced in step (5) is concentrated by four-effect vacuum concentration, the evaporation temperature of the first effect is controlled to be 105° C., the evaporation temperature of the last effect is controlled to be 56° C., the vacuum degree of the last effect is controlled to be 16 kPa, and the evaporation concentration is 16.5 times. Finally, the concentrated liquid is cooled to 30° C. and the cooled concentrated liquid is separated. The filtrate obtained by separation is returned to step (5) for treatment. The solid obtained by separation is ammonium sulfate crystals, totaling 454 g, with a recovery rate of 89.0%.

[0087] (7) The pH value of the primary fresh water produced in step (5) is controlled at 5.0, and the fresh water enters the secondary electrodialysis treatment, and the treatment is carried out under the conditions of an operating voltage of 0.9 V for each pair of membranes and a temperature of 25° C. When the conductivity of the secondary fresh water drops to 2000 μs / cm, the operation is stopped, and 2980 mL of secondary concentrated water and 2900 mL of secondary fresh water are obtained respectively.

[0088] (8) The pH value of the secondary concentrated water produced in step (7) is adjusted to 3.2, and four-effect vacuum concentration is adopted, the first-effect evaporation temperature is controlled at 88° C., the second-effect evaporation temperature is 52° C., the second-effect vacuum degree is 14 kPa, and the concentration is 2.3 times; then single-effect negative pressure evaporation is adopted, the evaporation temperature is controlled at 52° C., the single-effect evaporation absolute pressure is 14 kPa, and the evaporation concentration is 8 times.

[0089] (9) The concentrated liquid produced in step (8) is cooled and crystallized, and the cooling rate is controlled to be 2.0° C. / h. It is finally cooled to 18° C. and separated by a three-legged centrifuge. The liquid obtained by centrifugation is returned to step (7) and combined with the secondary fresh water. The solid obtained by centrifugation is glutamic acid crystals, totaling 97.8 g. The recovery rate of glutamic acid is 61.8%, and the purity is 87.2%.

[0090] (10) The secondary dilute produced in step (7) is concentrated by four-effect vacuum concentration, with the first-effect evaporation temperature controlled at 105° C., the second-effect evaporation temperature controlled at 56° C., and the second-effect vacuum degree controlled at 14 kPa. Concentration is stopped when the solid concentration reaches 55%.

[0091] (11) adding concentrated sulfuric acid to the concentrated solution produced in step (10) for hydrolysis, wherein the concentration of the concentrated sulfuric acid is 98 wt %, the amount added is 45% of the volume of the concentrated solution, the hydrolysis temperature is 135° C., and the hydrolysis time is 1.5 hours; after the hydrolysis is completed, the hydrolyzate and humus are obtained by plate and frame filtration.

[0092] (12) Add activated carbon to the hydrolyzate produced in step (11) in an amount of 1.5% (m / v) of the volume of the hydrolyzate, mix well, decolorize at 60° C. for 80 min, and then filter through a plate and frame to obtain a hydrolyzed decolorized solution.

[0093] (13) 6000 mL of concentrated fermentation broth, wherein the glutamic acid concentration is 340 g / L, is taken and the fermentation broth is subjected to an isoelectric process using the hydrolysis decolorization solution produced in step (9); then 1877.2 g of glutamic acid is separated to obtain 6900 mL of isoelectric mother liquor, wherein the glutamic acid concentration in the mother liquor is 22 g / L, and the calculated glutamic acid yield is 96.2%.

[0094] Comparative Example 1

[0095] The steps in Example 1 were followed, except that the pore size of the ceramic membrane selected in step (1) was adjusted to 300 nm and the operating pressure was adjusted to 0.8 MPa. The remaining conditions and steps were the same as in Example 1. The turbidity of the obtained ceramic membrane clear liquid was 25 NTU.

[0096] The final ammonium sulfate recovery rate dropped to 10%, and the final total glutamic acid recovery rate was 93.2%, which was lower than the recovery rates of glutamic acid and ammonium sulfate in Example 1 under the optimal conditions, but had little effect on obtaining dry bacterial protein.

[0097] Comparative Example 2

[0098] The steps in Example 1 are referred to, wherein only step (4) is omitted, that is, the ceramic membrane clear liquid obtained in step (3) is directly input into step (5) for electrodialysis, and the remaining conditions and steps are the same as in Example 1.

[0099] The final yields of ammonium sulfate and glutamic acid obtained are not much different from those in Example 1, but the bacterial protein decreases by more than 15%, the sulfuric acid consumption increases by 8%, the equipment investment increases by more than 160%, and the operating cost increases by more than 150%. The actual economic benefits are far lower than the benefits of Example 1 under the optimal conditions.

[0100] Comparative Example 3

[0101] The steps in Example 1 were followed, except that in step (5) the operation was stopped when the conductivity of the primary fresh water was controlled to be 5 mS / cm. Other conditions were the same as those in Example 1.

[0102] The bacterial protein finally obtained was basically the same as that in Example 1, and the ammonium sulfate yield increased by 6% compared with that in Example 1. However, the glutamic acid yield in step (9) decreased to 48.9%, and the total glutamic acid yield decreased to 94.2%. The value of glutamic acid was much higher than that of ammonium sulfate, so the economic benefit was lower than that in Example 1 under the optimal conditions.

[0103] Comparative Example 4

[0104] The steps in Example 1 were followed, except that in step (5) the operation was stopped when the conductivity of the primary fresh water was controlled to be 50 mS / cm. The other conditions were the same as those in Example 1.

[0105] The bacterial protein finally obtained was basically the same as that in Example 1, but the ammonium sulfate yield was lower than that in Example 1 by more than 22%, and the total glutamic acid yield was 90.4%, which was lower than the yields of glutamic acid and ammonium sulfate in Example 1 under the optimal conditions.

[0106] Comparative Example 5

[0107] The steps in Example 1 are followed, wherein only in step (7) the membrane operating voltage of the secondary electrodialysis is adjusted to 0.4 V, and the other conditions are the same as in Example 1.

[0108] The final production cycle was extended by 140%, the cleaning cycle of the secondary electrodialysis equipment was increased by more than 120%, and the yield of glutamic acid obtained in step (9) was 8.2 percentage points lower than that in Example 1. The production cost was higher than that in Example 1, and the economic benefit was also lower than that produced in Example 1 under the optimal conditions.

[0109] Comparative Example 6

[0110] The steps in Example 1 are referred to, wherein only in step (7) the membrane operating voltage of the secondary electrodialysis is adjusted to 1.3 V, and the other conditions are the same as in Example 1.

[0111] The yield of glutamic acid obtained in the final step (9) is only 48.7%, which is 27.4 percentage points lower than that in Example 1, and the total yield of glutamic acid is reduced to 91.2%. Therefore, the economic benefit is far lower than the economic benefit produced in Example 1 under the optimal conditions.

[0112] Comparative Example 7

[0113] The steps in Example 1 are referred to, wherein only in step (7) the secondary fresh water conductivity of the secondary electrodialysis is adjusted to 0.5 mS / cm and the operation is stopped. Other conditions are the same as in Example 1.

[0114] The yield of glutamic acid obtained in the final step (9) was reduced to 55.3%, and the total yield of glutamic acid was reduced to 95.8%, so the economic benefit was lower than the economic benefit produced in Example 1 under the optimal conditions.

[0115] Comparative Example 8

[0116] The steps in Example 1 are referred to, wherein only in step (7) the secondary fresh water conductivity of the secondary electrodialysis is adjusted to 8 mS / cm and the operation is stopped. Other conditions are the same as in Example 1.

[0117] The glutamic acid yield in the final step (9) decreased to 42.9%, and the total glutamic acid yield decreased to 94.6%, so the economic benefit was lower than that produced in Example 1 under the optimal conditions.

[0118] Comparative Example 9

[0119] The steps were carried out in accordance with Example 1, wherein only the pH of the primary fresh water in the secondary electrodialysis was adjusted to 3.4 in step (7), and the other conditions were the same as in Example 1.

[0120] The final operation could not reach the electrodialysis endpoint requirement of Example 1, and the subsequent steps could not be continued, and the comparative example failed.

[0121] Comparative Example 10

[0122] The steps were carried out in accordance with Example 1, wherein only the pH of the primary fresh water in the secondary electrodialysis was adjusted to 8.0 in step (7), and the other conditions were the same as those in Example 1.

[0123] Ultimately, the total yield of glutamic acid and the yield of glutamic acid in step (9) were not greatly affected, but its purity decreased by more than 15%, and the amount of alkali consumed for adjusting pH increased by more than 2 times, so the economic benefit was lower than the economic benefit produced in Example 1 under the optimal conditions.

[0124] Comparative Example 11

[0125] The steps in Example 1 are referred to, wherein step (7) is omitted, i.e., the primary fresh water is directly subjected to four-effect reduced pressure concentration and cooling crystallization.

[0126] The amount of bacterial protein and ammonium sulfate finally obtained was basically the same as that in Example 1, and the yield of glutamate was 4.2 percentage points lower than that in step (9) of Example 1. However, the purity of the obtained glutamate was only 40.3%, which was lower than the yield of glutamate in Example 1 under the optimized conditions.

[0127] Comparative Example 12

[0128] The steps in Example 1 were followed, except that in step (9) the amount of activated carbon added was adjusted to 0.1% of the volume of the hydrolyzate. Other conditions were the same as in Example 1.

[0129] The final bacterial protein and ammonium sulfate produced are not much different from those in Example 1, but the total yield of glutamic acid is only 92.5%, and the glutamic acid is dark in color, which brings great operating costs to the subsequent purification of glutamic acid. Therefore, the economic benefit is far lower than the economic benefit produced in Example 1 under the optimal conditions.

[0130] Comparative Example 13

[0131] The steps in Example 1 were followed, except that in step (11), the proportion of concentrated sulfuric acid added was adjusted to 10% of the volume of the concentrated solution. Other conditions were the same as in Example 1.

[0132] The final bacterial protein and ammonium sulfate produced are not much different from those in Example 1, but the total yield of glutamic acid is only 89.8%, so the economic benefit is far lower than the economic benefit produced in Example 1 under the optimal conditions.

[0133] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for improving the yield of glutamic acid by using a glutamic acid isoelectric mother liquor to form a ring process, characterized in that: The method comprises: The glutamic acid and other electrolyte mother liquors are first treated with a ceramic membrane to obtain a ceramic membrane clear solution and a ceramic membrane concentrated solution; the ceramic membrane concentrated solution is subjected to heat denaturation and then filtered to obtain bacterial protein and filtered clear solution, and the filtered clear solution is returned to the ceramic membrane for treatment; the ceramic membrane clear solution is treated with an ultrafiltration membrane to obtain an ultrafiltration concentrate and an ultrafiltration clear solution, and the ultrafiltration concentrate is returned for heat denaturation and filtration; The ultrafiltration clear liquid is treated by primary electrodialysis, and the membrane voltage is controlled to be maintained at 0.7-0.9V. When the conductivity of the primary fresh water is 10-20mS / cm, the electrodialysis is stopped to obtain primary concentrated water and primary fresh water; the primary concentrated water is subjected to reduced pressure concentration, evaporation crystallization and solid-liquid separation to obtain ammonium sulfate crystals, and the separated filtrate is returned to the primary electrodialysis treatment; the primary fresh water is adjusted to pH 4.5-7.0 and then subjected to secondary electrodialysis, and the membrane voltage is controlled to be maintained at 0.7-0.9V. When the conductivity of the secondary fresh water is 2-5mS / cm, the electrodialysis is stopped to obtain secondary concentrated water and secondary fresh water; The pH of the secondary concentrated water is adjusted to 3-4, and then it is concentrated under reduced pressure, cooled for crystallization, and solid-liquid separated to obtain glutamate crystals. All the filtrate obtained from the solid-liquid separation is recycled back to the secondary fresh water. After the secondary fresh water is concentrated under reduced pressure, it is hydrolyzed with acid, and then filtered and decolorized to obtain a hydrolyzed decolorized liquid. The hydrolyzed decolorized liquid is used for adjusting the isoelectricity of the glutamate fermentation liquid, and glutamate can be separated again.

2. The method according to claim 1, characterized in that The ceramic membrane used in the ceramic membrane treatment has a pore size of 10-50 nm, an operating pressure of 0.2-0.6 MPa, an operating temperature of 35-60° C., a membrane surface flow rate of 3-6 m / s, and an outlet water turbidity of ≤0.1 NTU.

3. The method according to claims 1 to 2, characterized in that: The thermal denaturation is as follows: heating the ceramic membrane concentrate to 60-90° C. for 10-50 minutes; adding sodium polyacrylate during the thermal denaturation; the amount of sodium polyacrylate added is 300-600 ppm.

4. The method according to claims 1 to 3, characterized in that: The molecular weight cut-off in the ultrafiltration membrane treatment is 5 to 500 kDa, the operating pressure is 0.1 to 0.6 MPa, the operating temperature is 25 to 60° C., and the membrane surface flow rate is 2 to 4 m / s.

5. The method according to claims 1 to 4, characterized in that: The reduced pressure concentration of the primary concentrated water is carried out by a four-effect falling film evaporator. The evaporation temperature of the first effect is controlled at 100-120°C, the evaporation temperature of the last effect is controlled at 45-60°C, the vacuum degree of the last effect is 10-20 kPa, and the evaporation concentration is 10-20 times.

6. The method according to claims 1 to 5, characterized in that The vacuum concentration of secondary concentrated water is as follows: firstly, four-effect vacuum concentration is adopted, the first-effect evaporation temperature is controlled at 85-90℃, the second-effect evaporation temperature is controlled at 45-60℃, the second-effect vacuum degree is 10-20kPa, and the concentration is 2-5 times; then, single-effect negative pressure evaporation is adopted, the evaporation temperature is controlled at 45-55℃, the single-effect evaporation absolute pressure is controlled at 10-20kPa, and the evaporation concentration is 5-10 times.

7. The method according to claims 1 to 6, characterized in that The cooling crystallization of secondary concentrated water is as follows: cooling to 10-35°C at a cooling rate of 1-3°C / h.

8. The method according to claims 1 to 7, characterized in that The reduced pressure concentration of secondary fresh water is carried out by a multi-effect falling film evaporator. The evaporation temperature of the first effect is controlled at 90-105°C, the evaporation temperature of the last effect is controlled at 45-60°C, the vacuum degree of the last effect is controlled at 10-20 kPa, and the concentration is stopped when the solid concentration is 50-65%.

9. The method according to claims 1 to 8, characterized in that The acid hydrolysis of the secondary fresh water is carried out using concentrated sulfuric acid; the concentration of the concentrated sulfuric acid is 95-98wt%, and the amount of concentrated sulfuric acid added is 30-50% of the volume of the secondary fresh water concentrated under reduced pressure; the temperature of the acid hydrolysis is 120-150°C, and the hydrolysis time is 1-3 hours.

10. The method according to claims 1 to 9, characterized in that The decolorization is activated carbon decolorization or membrane decolorization.

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