A method for producing feed using glutamic acid isoelectric mother liquor

Abstract

The application discloses a method for producing feed by using glutamic acid isoelectric mother liquor, and belongs to the technical field of industrial fermentation. The technical scheme of the application comprises the following steps: first, the glutamic acid isoelectric mother liquor is subjected to ceramic membrane and ultrafiltration membrane treatment to obtain membrane filtrate and concentrated solution; the concentrated solution is subjected to plate and frame filtration and drying to obtain bacterial protein; the obtained membrane filtrate is subjected to electrodialysis treatment to obtain concentrated water and dilute water; the concentrated water is subjected to evaporation crystallization and solid-liquid separation to obtain ammonium sulfate crystals; and the dilute water is subjected to concentration and drying to obtain feed protein, so that the method for producing feed from the glutamic acid isoelectric mother liquor is realized. The treatment method can increase the yield of feed, improve the yield of ammonium sulfate and bacterial protein, and has great economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to a method for producing feed using isoelectric mother liquor of glutamic acid, belonging to the field of industrial fermentation technology. Background Technology

[0002] Currently, glutamic acid production in China mainly relies on 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 industry primarily uses a "concentrated isoelectric extraction process," which typically yields 85–88% of the extracted product. The resulting mother liquor is called the isoelectric mother liquor. This mother liquor contains not only microbial cells, ammonium sulfate (approximately 70–120 g / L), and glutamic acid (20–35 g / L), but also some high-value soluble proteins, miscellaneous amino acids, and residual sugars. Due to the presence of impurities such as microbial cells and ammonium sulfate, some high-value components in the isoelectric mother liquor, such as glutamic acid, soluble proteins, and miscellaneous amino acids, cannot be directly recovered. Furthermore, the high concentration of ammonium sulfate prevents biochemical treatment of the mother liquor. Given my country's annual glutamic acid production of over 3 million tons, the low-level treatment of the isoelectric mother liquor not only results in the unrecoverable large quantities of high-value products, causing significant economic losses, but also causes severe environmental damage.

[0003] Currently, the most common methods for treating isoelectric mother liquor are concentration and spray drying to convert it into fertilizer, thereby reducing its environmental pollution. However, the production and sale of fertilizer are limited by factors such as the generation of large amounts of waste gas, low fertilizer efficiency, and poor fertilizer solubility. Furthermore, the low glutamic acid extraction yield, high operating costs of fertilizer production from isoelectric mother liquor, and the continued presence of waste gas pollution also reduce the profitability of monosodium glutamate (MSG) production enterprises, hindering their healthy development.

[0004] Among the existing technologies related to the use of isoelectric mother liquor, patent CN 103772013 A (Producing Rice-Specific Fertilizer with Slow-Release Effect Using MSG Mother Liquor) discloses the use of Bacillus licheniformis strains to ferment MSG mother liquor to produce γ-PGA, by adding a certain proportion of NH4 to meet the needs of rice growth. + The patent describes a technical solution for producing slow-release rice-specific fertilizer using ammonium sulfate (P) and potassium sulfate (K). However, this patent does not address the recovery of ammonium sulfate, and the fermentation process involved lasts for several days, which is excessively time-consuming. Patent CN 102533884 A (A Clean Production Method of Glutamic Acid, γ-Polyglutamic Acid, and Organic Fertilizer) discloses a method for sequentially preparing glutamic acid, γ-polyglutamic acid, and a water-retaining and moisture-retaining organic slow-release fertilizer using microbial fermentation. Similarly, this patent does not address the recovery of ammonium sulfate, and the process steps are overly cumbersome.

[0005] Furthermore, CN 110407388 A (A method for resource recovery of waste liquid from isoelectric extraction of concentrated glutamic acid) discloses a method for resource recovery of waste liquid from isoelectric extraction of concentrated glutamic acid. This method involves first treating the waste liquid from isoelectric extraction of concentrated glutamic acid through an ultrafiltration membrane to obtain a membrane concentrate and a membrane filtrate. The membrane concentrate is then filtered and dried to obtain bacterial protein. The membrane filtrate is decolorized with activated carbon and then subjected to electrodialysis to obtain an electrodialysis retentate and an electrodialysis permeate. The electrodialysis retentate and electrodialysis permeate are then concentrated by evaporation, cooled by crystallization, and separated to recover glutamic acid and ammonium sulfate, respectively. However, this method does not address the recovery of protein from the isoelectric mother liquor.

[0006] Therefore, it is necessary to continue to find a method to produce other high-value by-products from the isoelectric mother liquor of glutamic acid, effectively retaining and separating nutrients such as protein in the isoelectric mother liquor while separating ammonium sulfate, and preparing it into a feed with high protein content. Summary of the Invention

[0007] Technical issues

[0008] The isoelectric mother liquor of glutamic acid contains many nutrients with high secondary value, which can be separated and utilized. However, existing technologies mostly use it as a culture medium, which involves complex steps and does not address the recovery of ammonium sulfate from the isoelectric mother liquor.

[0009] Technical solution

[0010] To address the aforementioned problems, this invention provides a method for treating glutamic acid isoelectric mother liquor using technologies such as ultrafiltration separation, thermal denaturation, multi-effect concentration, evaporation crystallization, solid-liquid separation, and electrodialysis. This method enables the production of feed protein from the isoelectric mother liquor while simultaneously recovering microbial protein and ammonium sulfate. Furthermore, the condensate generated during evaporation and concentration can be recycled back into the production process, ultimately achieving the goal of high-value utilization of the isoelectric mother liquor. This method not only yields high-value feed protein but also recovers large quantities of ammonium sulfate and microbial protein, eliminates environmental pollution from high-concentration isoelectric mother liquor and waste gas, and reduces water consumption due to the recycling of evaporation condensate. Therefore, it not only achieves considerable economic benefits but also provides significant environmental benefits.

[0011] This invention provides a method for producing feed using isoelectric mother liquor of glutamic acid, the method comprising:

[0012] The isoelectric mother liquor of glutamic acid is first treated with a ceramic membrane to obtain a clear ceramic membrane solution and a concentrated ceramic membrane solution. The concentrated ceramic membrane solution is then heat-denatured and filtered to obtain microbial protein and a clear filtrate. The clear filtrate is returned to the ceramic membrane treatment. The clear ceramic membrane solution is then treated with an ultrafiltration membrane to obtain an ultrafiltration concentrate and an ultrafiltration clear solution. The ultrafiltration concentrate is returned to the heat denaturation and filtration processes. The pH of the ultrafiltration clear solution is adjusted and then treated with electrodialysis to obtain concentrated water and desalinated water. The concentrated water is then concentrated under reduced pressure, evaporated for crystallization, and separated into solid and liquid components to obtain ammonium sulfate crystals. The separated filtrate is returned to the electrodialysis treatment. The desalinated water is adjusted to pH, concentrated under reduced pressure, and then dried to obtain the feed.

[0013] Furthermore, the ceramic membrane treatment removes bacterial cells and large molecular proteins from the isoelectric mother liquor, facilitating subsequent separation and purification operations; 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 effluent turbidity ≤0.1 NTU.

[0014] Furthermore, the thermal denaturation is achieved by heating the concentrated bacterial protein to denature it, thereby facilitating subsequent separation; the thermal denaturation is performed by heating the ceramic membrane concentrate to 60-90°C for 10-50 minutes; the heat source for heating can be steam.

[0015] Furthermore, sodium polyacrylate may be added during the heat denaturation process; the amount of sodium polyacrylate added is 300-600 ppm.

[0016] Furthermore, the filtration can be selected as plate and frame filtration, that is, using a plate and frame filter for filtration.

[0017] Furthermore, the ultrafiltration membrane treatment has a molecular weight cutoff of 5–500 kDa, an operating pressure of 0.1–0.6 MPa, an operating temperature of 25–60 °C, and a membrane surface flow rate of 2–4 m / s.

[0018] Furthermore, the pH of the ultrafiltrate is adjusted to 3-4.

[0019] Furthermore, the parameters for the electrodialysis treatment are as follows: the membrane voltage is maintained at 0.7–0.9V, the operating temperature is 20–35℃, and electrodialysis is stopped when the conductivity of the freshwater is 10–20 mS / cm.

[0020] Furthermore, the concentrated water is concentrated under reduced pressure using a multi-effect falling film evaporator or a rising film evaporator.

[0021] Preferably, the concentrated water is concentrated under reduced pressure using a multi-effect falling film evaporator; the multi-effect falling film evaporator is a four-effect falling film evaporator.

[0022] Furthermore, the concentration factor of concentrated water under reduced pressure is between 10 and 20 times.

[0023] Specifically, the concentrated water can be concentrated under reduced pressure using a four-effect falling film evaporator, with the first-effect evaporation temperature controlled at 100-120℃, the uneffect evaporation temperature at 50-60℃, the uneffect vacuum degree at 10-20kPa, and the evaporation concentration at 10-20 times.

[0024] Furthermore, the temperature for the evaporation and crystallization of concentrated water is 40–60°C.

[0025] Furthermore, solid-liquid separation of concentrated water can be carried out using a conical centrifuge or a scraper centrifuge; the temperature should be controlled at 20-60℃ during centrifugation.

[0026] Furthermore, the pH of the freshwater is adjusted to 6-7.

[0027] Furthermore, the depressurized concentration of freshwater is carried out using a multi-effect falling film evaporator or a rising film evaporator.

[0028] Preferably, the depressurized concentration of fresh water is carried out using a multi-effect falling film evaporator; the multi-effect falling film evaporator is a four-effect falling film evaporator.

[0029] Specifically, the depressurized concentration of fresh water can be carried out using a four-effect falling film evaporator, with the evaporation temperature of the first effect controlled at 90-110℃, the evaporation temperature of the uneffected effect controlled at 50-60℃, and the vacuum degree of the uneffected effect controlled at 10-20 kPa. Concentration is stopped when the solids concentration reaches 40-65%.

[0030] Furthermore, the drying of freshwater after vacuum concentration can be achieved by spray drying or drum drying.

[0031] In this invention, the isoelectric mother liquor of glutamic acid is first treated with a ceramic membrane, and the concentrate undergoes thermal denaturation. Then, it is filtered through a plate and frame filter to obtain microbial protein and the clarified liquid. The microbial protein can be sold as feed protein. During electrodialysis of the ultrafiltrate, by controlling the conductivity at the endpoint of electrodialysis, ammonium sulfate is concentrated in the concentrated water, while glutamic acid and other small-molecule proteins are concentrated in the fresh water, achieving more precise substance separation while retaining as much protein as possible. The concentrated water is then concentrated through multi-effect evaporation, and solid-liquid separation yields ammonium sulfate crystals. The resulting filtrate is then returned to electrodialysis for further treatment, thereby increasing the yield of ammonium sulfate, which can be sold as fertilizer. Fresh water contains a large amount of glutamic acid, as well as a certain amount of other amino acids, small-molecule proteins, and residual sugars. These components are essential for feed. After multi-effect concentration of the fresh water to a certain solid content, it is dried or incorporated into feed to improve the nutritional value of the feed, thus achieving the goal of producing feed protein using the isoelectric mother liquor of glutamic acid.

[0032] The beneficial effects achieved by this invention are as follows:

[0033] 1. This invention can recover more than 98% of the bacterial protein and more than 85% of the ammonium sulfate in the isoelectric mother liquor, increasing the production of ammonium sulfate by 450 kg and feed by 290 kg per ton of monosodium glutamate, and increasing the economic benefits of monosodium glutamate by more than 600 yuan per ton.

[0034] 2. This invention achieves the separation of ammonium sulfate, glutamic acid, and protein in the isoelectric mother liquor by regulating the conductivity at the endpoint of electrodialysis, while retaining as much protein as possible, so that the protein content in the feed exceeds 50%, thereby meeting the production requirements of high protein content in feed and the complete resource utilization of the isoelectric mother liquor. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall process of a method for producing feed using isoelectric mother liquor of glutamic acid according to the present invention. Detailed Implementation

[0036] Detection methods

[0037] Method for determining glutamate content: The SBA-40 biosensor was used for determination.

[0038] Ammonium sulfate content determination method: The determination shall be carried out in accordance with the national standard GB / T 535-2020.

[0039] Solid content determination method: Abbe refractometer was used for determination.

[0040] Protein content determination method: Kjeldahl method was used for determination.

[0041] The present invention will be combined with Figure 1 The following is a further description in the form of an embodiment:

[0042] Instrument use

[0043] The four-effect vacuum concentration is carried out using a four-effect falling film evaporation system, which was purchased from a subsidiary of Shanghai Shennong Energy Conservation and Environmental Protection Technology Co., Ltd., model FM-4; the plate and frame filtration is carried out using a plate and frame filter press, which was purchased from Haining Yongsheng Membrane Filtration Equipment Manufacturing Co., Ltd., model YSW150-10; the electrodialysis treatment system was purchased from Shandong Tianwei Membrane Technology Co., Ltd., model TWED-2-20.

[0044] Example 1

[0045] (1) Take 3000 mL of glutamic acid isoelectric mother liquor (glutamic acid concentration is 28 g / L, ammonium sulfate is 92 g / L) and pass it through a 20 nm ceramic membrane. The operating pressure is 0.4 MPa, the operating temperature is 45 °C, and the membrane surface flow rate is controlled at 5 m / s. 2770 mL of ceramic membrane clear liquid and 230 mL of ceramic membrane concentrated liquid are obtained. The turbidity of the ceramic membrane clear liquid is 0.005 NTU.

[0046] (2) The ceramic membrane concentrate from step (1) was heated to 85°C, and then polyammonium acrylate (PAAS) was added at a concentration of 450 ppm and mixed. The mixture was maintained for 30 min, and then filtered by plate and frame filter press to obtain 142 mL of filtrate and 85 g of filter cake. The filtrate was recycled back to step (1) to obtain ceramic membrane clear liquid. The filter cake was dried to obtain 44.6 g of dried bacterial protein.

[0047] (3) A total of 2912 mL of the ceramic membrane clear solution obtained in steps (1) and (2) was mixed, with a glutamic acid concentration of 28 g / L and an ammonium sulfate concentration of 92 g / L.

[0048] (4) The ceramic membrane clear liquid obtained in step (3) is treated with an ultrafiltration membrane with a molecular weight cutoff of 300kDa. The operating temperature is controlled at 25℃, the operating pressure is 0.15MPa, and the membrane surface flow rate is 2m / s to obtain membrane filtrate and membrane concentrate. The obtained membrane concentrate is returned to step (1) for treatment. Then, the obtained ceramic membrane clear liquid is taken back to the ultrafiltration membrane for treatment to obtain membrane filtrate. A total of 2901mL of membrane filtrate is obtained from the two ultrafiltration processes.

[0049] (5) The membrane filtrate produced in step (4) enters the electrodialysis treatment system, the feed pH is controlled at 3.2, and the treatment is carried out under the conditions of 0.9V operating voltage and 25℃ for each pair of membranes. When the conductivity of the fresh water drops to 15mS / cm, the operation is stopped, and 4300mL of concentrated water and 1500mL of fresh water are obtained respectively.

[0050] (6) The concentrated water produced in step (5) is concentrated by four-effect vacuum, the evaporation temperature of the first effect is controlled at 118°C, the evaporation temperature of the uneffect is 58°C, the vacuum degree of the uneffect is 18kPa, the evaporation concentration is 14 times, and the water is cooled to 40°C. The filtrate is separated and returned to step (5) for processing. The solid obtained is ammonium sulfate crystals, totaling 239g, with a yield of 86.6%.

[0051] (7) Control the pH of the freshwater produced in step (5) at around 6.2, use a four-effect vacuum concentration, control the evaporation temperature of the first effect to be 108℃, the evaporation temperature of the uneffect to be 58℃, the vacuum degree of the uneffect to be 18kPa, and stop the concentration when the solid concentration reaches 45%.

[0052] (8) Spray dry the concentrate produced in step (7) to obtain 180g of feed, of which the protein content is 56%.

[0053] Example 2

[0054] (1) Take 3500 mL of glutamic acid isoelectric mother liquor (glutamic acid concentration is 23 g / L, ammonium sulfate concentration is 82 g / L) and pass it through a 30 nm ceramic membrane. The operating pressure is 0.3 MPa, the operating temperature is 40 °C, and the membrane surface flow rate is controlled at 4 m / s to obtain 3180 mL of ceramic membrane clear liquid and 320 mL of ceramic membrane concentrated liquid. The turbidity of the ceramic membrane clear liquid is 0.05 NTU.

[0055] (2) The ceramic membrane concentrate from step (1) was heated to 80°C, and then PAAS was added at a concentration of 400 ppm and mixed. The mixture was maintained for 40 min, and then filtered by plate and frame filter press to obtain 225 mL of filtrate and 92 g of filter cake. The filtrate was recycled back to step (1) to obtain ceramic membrane clear liquid. The filter cake was dried to obtain 47.5 g of dried bacterial protein.

[0056] (3) Mix the ceramic membrane clear solution obtained in steps (1) and (2) to a total of 3300 mL, in which the concentration of glutamic acid is 23 g / L and the concentration of ammonium sulfate is 82 g / L.

[0057] (4) The ceramic membrane clear liquid obtained in step (3) is treated with an ultrafiltration membrane with a molecular weight cutoff of 50 kDa. The operating temperature is controlled at 35℃, 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. Then, the obtained ceramic membrane clear liquid is taken back to the ultrafiltration membrane for treatment to obtain membrane filtrate. A total of 3292 mL of membrane filtrate is obtained from the two ultrafiltration processes.

[0058] (5) The membrane filtrate produced in step (4) enters the electrodialysis treatment system, the feed pH is controlled at 3.1, and the treatment is carried out under the conditions of 0.8V operating voltage and 30℃ for each pair of membranes. When the conductivity of the fresh water drops to 12mS / cm, the operation is stopped, and 4900mL of concentrated water and 1650mL of fresh water are obtained respectively.

[0059] (6) The concentrated water produced in step (5) is concentrated by four-effect vacuum, the evaporation temperature of the first effect is controlled at 108°C, the evaporation temperature of the uneffect is controlled at 58°C, the vacuum degree of the uneffect is controlled at 18kPa, the evaporation concentration is 15.5 times, cooled to 35°C, the filtrate is separated and returned to step (5) for processing, the solid obtained is ammonium sulfate crystals, a total of 262g, the yield is 91.2%.

[0060] (7) Control the pH of the fresh water produced in step (5) at around 6.5, use a four-effect vacuum concentration, control the evaporation temperature of the first effect to be 100℃, the evaporation temperature of the uneffect to be 56℃, the vacuum degree of the uneffect to be 16kPa, and stop the concentration when the solid concentration reaches 55%.

[0061] (8) Spray the concentrated liquid produced in step (7) onto the corn husks and dry it in a drum to obtain 189g of feed, of which the protein content is 54%.

[0062] Example 3

[0063] (1) Take 4000 mL of glutamic acid isoelectric mother liquor (glutamic acid concentration is 26 g / L, ammonium sulfate concentration is 88 g / L) and pass it through a 20 nm ceramic membrane. The operating pressure is 0.5 MPa, the operating temperature is 50 °C, and the membrane surface flow rate is controlled at 5 m / s. 3760 mL of ceramic membrane clear liquid and 240 mL of ceramic membrane concentrated liquid are obtained. The turbidity of the ceramic membrane clear liquid is 0.02 NTU.

[0064] (2) The ceramic membrane concentrate from step (1) was heated to 70°C, and then PAAS was added at a concentration of 420 ppm and mixed. The mixture was maintained for 50 min, and then filtered by plate and frame filter press to obtain 145 mL of filtrate and 99 g of filter cake. The filtrate was recycled back to step (1) to obtain ceramic membrane clear liquid. The filter cake was dried to obtain 54.2 g of dried bacterial protein.

[0065] (3) A total of 3910 mL of the ceramic membrane clear solution obtained in steps (1) and (2) was mixed, with a glutamic acid concentration of 26 g / L and an ammonium sulfate concentration of 88 g / L.

[0066] (4) The ceramic membrane clear liquid obtained in step (3) is treated with an ultrafiltration membrane with a molecular weight cutoff of 5 kDa. The operating temperature is controlled at 30℃, 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. Then, the obtained ceramic membrane clear liquid is taken back to the ultrafiltration membrane for treatment to obtain membrane filtrate. A total of 3890 mL of membrane filtrate is obtained from the two ultrafiltration processes.

[0067] (5) The membrane filtrate produced in step (4) enters the electrodialysis treatment system, the feed pH is controlled at 3.0, and the treatment is carried out under the conditions of 0.7V operating voltage and 25℃ for each pair of membranes. When the conductivity of the fresh water drops to 10mS / cm, the operation is stopped, and 5800mL of concentrated water and 1900mL of fresh water are obtained respectively.

[0068] (6) The concentrated water produced in step (5) is concentrated by four-effect vacuum concentration. The evaporation temperature of the first effect is controlled at 108°C, the evaporation temperature of the uneffect is controlled at 56°C, the vacuum degree of the uneffect is controlled at 16kPa, the evaporation concentration is 16.5 times, and the solution is cooled to 30°C. The filtrate is separated and returned to step (5) for processing. The solid obtained is ammonium sulfate crystals, totaling 325g, with a yield of 92.3%.

[0069] (7) The pH of the freshwater produced in step (5) is controlled at around 6.8. Four-effect vacuum concentration is adopted. The evaporation temperature of the first effect is controlled at 105℃, the evaporation temperature of the uneffect is 52℃, the vacuum degree of the uneffect is 14kPa, and the concentration is stopped when the solid concentration reaches 65%.

[0070] (8) Spray the concentrated liquid produced in step (7) onto the corn husks and dry it in a drum to obtain 238g of feed, of which the protein content is 51%.

[0071] Comparative Example 1

[0072] The procedure was carried out according to the steps in Example 1, except that the pore size of the ceramic membrane selected in step (1) was adjusted to 300 nm and the operating pressure was 0.8 MPa. The other conditions and steps were the same as in Example 1, and the turbidity of the obtained ceramic membrane clear liquid was 25 NTU.

[0073] Ultimately, 212.5g of ammonium sulfate and 160g of feed were obtained. The recovery rates of both feed and ammonium sulfate decreased by more than 10%, which was lower than the recovery rates of ammonium sulfate and feed under the optimal conditions in Example 1. However, it had little impact on obtaining dry microbial protein.

[0074] Comparative Example 2

[0075] The steps in Example 1 are followed, except that 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.

[0076] Ammonium sulfate was ultimately obtained, and the feed was similar to that of Example 1, but the microbial protein content decreased by more than 8%. Furthermore, the lack of ultrafiltration to remove impurities from the ceramic membrane supernatant would increase the electrodialysis operating time, and the estimated operating cost of electrodialysis would increase by more than 150%. Therefore, the actual economic benefits were far lower than those of Example 1 under optimal conditions.

[0077] Comparative Example 3

[0078] The steps in Example 1 are followed, except that the operation is stopped when the conductivity of fresh water is controlled to be 50 mS / cm in step (5), and the other conditions are the same as in Example 1.

[0079] The bacterial protein content was basically the same as in Example 1, but the ammonium sulfate yield was significantly lower than in Example 1, decreasing by 22 percentage points. Although the feed yield was higher than in Example 1, increasing by 10 percentage points, the feed protein content was only 31%. Considering all factors, the actual economic benefits were still far lower than those of Example 1 under optimal conditions.

[0080] Comparative Example 4

[0081] The steps in Example 1 are followed, except that the operation is stopped when the conductivity of fresh water is controlled to be 5 mS / cm in step (5), and the other conditions are the same as in Example 1.

[0082] The final bacterial protein content was basically the same as in Example 1, but the ammonium sulfate yield increased by 4 percentage points compared to Example 1. However, the feed yield decreased by 6.5 percentage points compared to Example 1, and the feed protein content also decreased. Since the feed value is much higher than the value of ammonium sulfate, its actual economic benefit is still lower than that of Example 1 under the optimal conditions.

[0083] Comparative Example 5

[0084] The steps were carried out in Example 1, except that the evaporation temperature in step (7) was controlled at 150°C, and the other conditions were the same as in Example 1. Concentration was stopped when the solid concentration reached 45%.

[0085] The final yields of microbial protein, ammonium sulfate, and feed were similar to those in Example 1, but the protein content of the feed was 15 percentage points lower than that in Example 1. Furthermore, the excessively high evaporation temperature required a large amount of heat energy to be provided in a short time, and the calculated operating costs were expected to increase by approximately 25%. Therefore, the economic benefits were far lower than those of Example 1 under optimal conditions.

[0086] Comparative Example 6

[0087] The steps were carried out in Example 1, except that the evaporation temperature in step (7) was controlled at 80°C, and the other conditions were the same as in Example 1. Concentration was stopped when the solid concentration reached 45%.

[0088] The yields of bacterial protein, ammonium sulfate, and feed produced were not significantly different from those in Example 1, and there was no significant difference in feed protein. However, the overall operating time increased significantly, by about 20% compared to the operating time in Example 1. Therefore, the economic benefits were far lower than those produced in Example 1 under optimal conditions.

[0089] Comparative Example 7

[0090] The steps in Example 1 are followed, except that the ineffective evaporation temperature in step (7) is controlled at 30°C, and the other conditions are the same as in Example 1.

[0091] The final bacterial protein and ammonium sulfate produced were not much different from those in Example 1, but it was impossible to concentrate them to a solids concentration of more than 40%, resulting in operational failure. If the solids concentration requirement was reduced, although the amount of feed obtained would not be significantly affected, the operating cost would increase by more than 30%. Therefore, the economic benefits were far lower than those of Example 1 under the optimal conditions.

[0092] Comparative Example 8

[0093] Refer to the steps of Example 1, except that the concentration of solids in step (7) is changed from 45% to 20%, while other conditions remain the same.

[0094] The final amount of ammonium sulfate and feed was not much different from that in Example 1, but the corresponding operating cost was more than 260% higher than that in Example 1, and the production time was extended by 20%. Therefore, the economic benefits were far lower than those of Example 1 under the optimal conditions.

[0095] Comparative Example 9

[0096] The steps of Example 1 were followed, except that the pH of the material in step (5) was adjusted to 5.0, and the other conditions were the same as in Example 1.

[0097] Although the final increase in ammonium sulfate production by 4% has little impact, feed production decreases by more than 20% and feed protein content decreases by more than 16%. Therefore, the economic benefits are lower than those generated under the optimal conditions in Example 1.

[0098] Comparative Example 10

[0099] The procedure was carried out in accordance with the steps of Example 1, except that the pH of the material in step (5) was adjusted to 1.5, and the other conditions were the same as in Example 1.

[0100] Although the final yield of ammonium sulfate increased by 3.5%, the feed yield decreased by more than 25% and the feed protein content decreased by more than 20%. Therefore, the economic benefits were lower than those of Example 1 under the optimal conditions.

[0101] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for producing feed using isoelectric mother liquor of glutamic acid, characterized in that, The method is as follows: The isoelectric mother liquor of glutamic acid is first treated with a ceramic membrane to obtain a clear ceramic membrane solution and a concentrated ceramic membrane solution. The concentrated ceramic membrane solution is then denatured by heat and filtered to obtain bacterial protein and a clear filtrate. The clear filtrate is returned to the ceramic membrane for further treatment. The clarified liquid from the ceramic membrane is treated with an ultrafiltration membrane to obtain an ultrafiltration concentrate and an ultrafiltration clarified liquid. The ultrafiltration concentrate is returned for heat denaturation and filtration. The ultrafiltration clarified liquid is adjusted to pH 3-4 and then treated with electrodialysis, maintaining the membrane voltage at 0.7-0.9 V. Electrodialysis is stopped when the conductivity of the desalinated water is 10-20 mS / cm, yielding concentrated water and desalinated water. The concentrated water is concentrated under reduced pressure, evaporated for crystallization, and then separated into solid and liquid components to obtain ammonium sulfate crystals. The filtrate obtained from the separation is returned for electrodialysis. The desalinated water is adjusted to pH 6-7, concentrated under reduced pressure, and then dried to obtain feed. 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℃, a membrane surface flow rate of 3-6 m / s, and an effluent turbidity ≤0.1 NTU. The thermal denaturation is achieved by heating the ceramic membrane concentrate to 60-90°C for 10-50 minutes; sodium polyacrylate is added during the thermal denaturation process; the amount of sodium polyacrylate added is 300-600 ppm. The ultrafiltration membrane treatment has a molecular weight cutoff of 5~500 kDa, an operating pressure of 0.1~0.6 MPa, an operating temperature of 25~60℃, and a membrane surface flow rate of 2~4 m / s. The depressurized concentration of fresh water is carried out using a four-effect falling film evaporator. The evaporation temperature of the first effect is controlled at 90~110℃, the evaporation temperature of the uneffect is controlled at 45~60℃, the vacuum degree of the uneffect is controlled at 10~20 kPa, and the concentration is stopped when the solid concentration reaches 40~65%.

2. The method according to claim 1, characterized in that, The concentrated water is concentrated under reduced pressure using a multi-effect falling film evaporator or a rising film evaporator.

3. The method according to claim 1, characterized in that, The concentrated water is concentrated under reduced pressure using a four-effect falling film evaporator. The evaporation temperature of the first effect is controlled at 100~120℃, the evaporation temperature of the last effect is 45~60℃, the vacuum degree of the last effect is 10~20kPa, and the evaporation concentration is 10~20 times.

4. The method according to claim 1, characterized in that, Solid-liquid separation of concentrated water is carried out using a conical centrifuge or a scraper centrifuge.

5. The method according to claim 1, characterized in that, Freshwater that has been concentrated under reduced pressure is dried using either spray drying or drum drying.

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