Process for improving monosodium glutamate crystallization by forced concentration

Abstract

The present application belongs to the technical field of monosodium glutamate production, and discloses a process for improving monosodium glutamate crystallization by forced concentration, comprising the following steps: 1) centrifugal separation, 2) ultrafiltration, 3) forced concentration, 4) isoelectric crystallization, 5) neutralization, and 6) separation of monosodium glutamate. The monosodium glutamate product obtained by the process has a white and glossy appearance, a uniform particle size, and a purity of more than 99.5%.

Description

Technical Field

[0001] This invention belongs to the field of monosodium glutamate (MSG) production technology, specifically relating to a process for improving MSG crystallization through forced concentration. Background Technology

[0002] Monosodium glutamate (MSG) is a food flavoring agent with a large market demand. The production method of obtaining glutamic acid through bio-fermentation and processing it into MSG is relatively mature. How to save production costs, improve product quality, and increase production capacity has become the goal of various enterprises.

[0003] The crystallization process for monosodium glutamate (MSG) generally involves neutralizing glutamic acid crystals to produce sodium glutamate, a technique that has been extensively studied. For example:

[0004] Reference 1: CN105039488A discloses a method for extracting monosodium glutamate (MSG) using concentrated isoelectric point technology. The method includes: separating glutamic acid fermentation broth into a bacterial paste and a glutamic acid supernatant via ultrafiltration; concentrating the glutamic acid supernatant to obtain a concentrated solution; isoelectric crystallization to separate the glutamic acid crystals; adding a 10% sodium carbonate aqueous solution to the glutamic acid crystals for dissolution and neutralization at a controlled temperature of 60-62℃ and a pH of 6.4-6.5; followed by evaporation and crystallization; and centrifugation to separate the MSG. This method focuses on addressing the technical problem of failing to meet energy conservation and emission reduction standards.

[0005] Reference 2: CN116114854A discloses a process for improving the crystallization rate and particle size of monosodium glutamate (MSG), comprising: step 1) filtration and adsorption, step 2) inoculation, step 3) crystallization, step 4) crystallization, and step 5) separation of the finished product. This process solves the problems existing in the MSG crystallization process, such as low crystallization rate, slow speed, and large particle size differences.

[0006] Reference 3, CN114287604A, discloses a method for producing a special crystalline monosodium glutamate (MSG), comprising the following steps: step 1) preparation of a neutralized monosodium glutamate solution; step 2) preparation of extra-large crystalline seed crystals; step 3) double-stage heating evaporation and concentration; and step 4) grading and sieving. This production method, through process improvement, produces a product with excellent crystalline form and quality, meeting the market demand for extra-large crystalline products.

[0007] Reference 4 (CN118206462A) discloses a process for improving the crystallization quality of glutamic acid using ultrasonic technology, comprising the following steps: α-glutamic acid suspension diluted with water to a concentration of 20-30°Bé is introduced into a crystallization tank, heated to 70-80℃, and under heat preservation conditions, ultrasonic waves are activated for 0.5-1.5 hours to obtain a β-type crystalline suspension. The suspension is allowed to settle naturally, the supernatant is removed by centrifugation, and then vacuum filtered, followed by washing to obtain wet glutamic acid, which is finally dried. This process, through optimization of the crystallization process, promotes crystallization efficiency and improves crystallization yield and quality.

[0008] Existing technologies have yielded numerous studies on the crystallization process of monosodium glutamate (MSG). For example, reference 4 mentioned above uses the method of completely converting the α-crystalline form of glutamic acid into the β-crystalline form to achieve crystal purification. Currently, the industry's main glutamic acid crystallization process employs a high-temperature crystallization process. This involves remelting the isoelectrically separated α-glutamic acid and then heating it to 90°C using an injector, maintaining the temperature for 2 hours to achieve the conversion from α-crystalline to β-crystalline form. However, this process consumes additional energy and fails to achieve energy conservation and emission reduction.

[0009] Previous research by the inventors (CN202410998843.9) showed that adding p-aminobenzoic acid to the fermentation broth produces high-purity α-crystalline glutamic acid with large, glossy particles, significantly improved yield and purity, and a correspondingly significant increase in apparent specific gravity. Building on this foundation, the inventors continued their research on the crystallization process of monosodium glutamate (MSG). Summary of the Invention

[0010] In order to overcome the technical defects of the existing technology, the present invention provides a process for improving monosodium glutamate crystallization by forced concentration.

[0011] The present invention is achieved through the following technical solution.

[0012] The process of increasing monosodium glutamate (MSG) crystallization by forced concentration includes:

[0013] Step 1) Centrifugation, Step 2) Ultrafiltration, Step 3) Forced concentration, Step 4) Isoelectric crystallization, Step 5) Neutralization, Step 6) Separation of monosodium glutamate.

[0014] Specifically, the process includes the following steps:

[0015] Step 1) Centrifugation: Add p-aminobenzoic acid to the glutamic acid fermentation broth, then centrifuge using a disc centrifuge and collect the supernatant liquid;

[0016] Step 2) Ultrafiltration: Then, ultrafiltration is performed through an ultrafiltration membrane, and the filtrate is collected;

[0017] Step 3) Forced concentration: The filtrate is concentrated using a plate double-effect evaporator to obtain a concentrated solution;

[0018] Step 4) Isoelectric crystallization: The solution is fed into a primary isoelectric tank, and then the pH of the concentrate is adjusted to the isoelectric point of glutamic acid, 3.2, using concentrated sulfuric acid. The solution is then gradually cooled at a rate of 4°C / h until the temperature reaches 20°C. The liquid from the primary isoelectric tank is then passed through a secondary isoelectric tank, where the solution is gradually cooled at a rate of 2°C / h until the temperature reaches 10°C, with the pH controlled at 3.2. Finally, the solution is centrifuged using a horizontal screw centrifuge to separate wet glutamic acid crystals, which are then dried at low temperature to obtain glutamic acid crystals.

[0019] Step 5) Neutralization: Add sodium carbonate aqueous solution to the glutamic acid crystals to dissolve and neutralize them. The neutralization temperature is controlled at 60℃ and the pH value is controlled at 6.5.

[0020] Step 6) Separate monosodium glutamate: Evaporate to crystallize, centrifuge to separate monosodium glutamate, and dry to obtain the final product.

[0021] Preferably, the amount of para-aminobenzoic acid added is 1-2 mg per liter of glutamic acid fermentation broth.

[0022] Preferably, the disc centrifuge separates the particles at a speed of 5000 rpm for 3 minutes.

[0023] Preferably, the ultrafiltration membrane has a molecular weight cutoff of 1000 Da.

[0024] Preferably, the concentration parameters are: concentration temperature of 80℃, vacuum degree of -0.06MPa, and concentration of 3-4 times. Preferably, the centrifugation speed of the horizontal screw centrifuge is 500-1500 rpm, and the centrifugation time is 5-10 min. Preferably, the mass fraction of the sodium carbonate aqueous solution is 10%.

[0025] The beneficial effects achieved by this invention mainly include, but are not limited to, the following aspects: In the initial stage of separation and purification of glutamic acid fermentation broth, the addition of p-aminobenzoic acid effectively avoids the formation of β-shaped crystals. During crystallization, p-aminobenzoic acid can adsorb onto the crystal surface and enter the crystal interior, affecting glutamic acid crystallization. P-aminobenzoic acid has a stronger inhibitory effect on β-shaped crystals, allowing the broth to crystallize so that only α-shaped crystals precipitate, without transforming into β-shaped crystals. In industrial production, primary nucleation must be avoided, as it leads to the generation of a large number of crystal nuclei, resulting in small crystal particles that are difficult to separate. The addition of p-aminobenzoic acid can inhibit primary nucleation, preventing the generation of a large number of crystal nuclei and yielding larger, more uniform crystals. This invention, by adding p-aminobenzoic acid, prepares high-purity α-crystalline glutamic acid with large, glossy particles, significantly improved yield and purity, and a correspondingly significant increase in apparent specific gravity. The monosodium glutamate (MSG) product prepared using glutamic acid crystals has a white appearance, excellent gloss, uniform particle size, and a purity of over 99.5%. This invention uses a double-effect evaporator for forced concentration and crystallization, replacing the original single-effect concentration process. This reduces the steam consumption in the concentration and crystallization process to 60% of the original consumption. By using the double-effect evaporator, the crystal size is effectively controlled, providing a stable growth environment for the crystals, thereby ensuring the crystal structure and the proportion of qualified products. This effectively reduces the consumption of water, electricity, and steam, and improves product quality and monosodium glutamate (MSG) production. Detailed Implementation

[0026] Those skilled in the art can refer to the content of this document and appropriately improve the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The products and methods of this invention have been described through preferred embodiments, and those skilled in the art can obviously make modifications or appropriate alterations and combinations to the products and methods described herein without departing from the content, spirit, and scope of this invention to implement and apply the technology of this invention. To further understand this invention, the following detailed description is provided in conjunction with embodiments.

[0027] Example 1

[0028] A process for improving the crystallization efficiency and purity of monosodium glutamate (MSG) includes:

[0029] Add p-aminobenzoic acid to the glutamic acid fermentation broth (glutamic acid content 130g / L) at a ratio of 1mg:1L. Then, separate the broth using a disc centrifuge at 5000rpm for 3min. Collect the supernatant and then ultrafilter it through an ultrafiltration membrane (molecular weight cutoff of 1000Da). Collect the filtrate and concentrate it using a plate double-effect evaporator. Set the concentration temperature to 80℃ and the vacuum degree to -0.06MPa. Concentrate it 3 times to obtain the concentrate. Then, put it into a primary isoelectric tank. Then, use concentrated sulfuric acid to adjust the pH of the concentrate to the isoelectric point of glutamic acid 3.2. Gradually cool the broth at a rate of 4℃ / h until the temperature drops to 20℃. The liquid, after passing through the primary isoelectric point tank, then passes through the secondary isoelectric point tank, where the liquid is gradually cooled at a rate of 2℃ / h until it reaches 10℃, with the pH controlled at 3.2. It is then centrifuged using a horizontal screw centrifuge at 1000 rpm for 10 minutes to separate wet glutamic acid crystals. These crystals are then dried at low temperature to obtain glutamic acid crystals. A 10% sodium carbonate aqueous solution is added to the glutamic acid crystals to dissolve and neutralize them at 60℃ and pH 6.5. The crystals are then evaporated and crystallized, and the monosodium glutamate (MSG) is separated by centrifugation and dried to obtain the final product. The resulting MSG product has a white appearance, excellent gloss, uniform particle size, and a purity of over 99.5%.

[0030] Example 2

[0031] A process for improving the crystallization efficiency and purity of monosodium glutamate (MSG) includes:

[0032] Para-aminobenzoic acid was added to the glutamic acid fermentation broth (glutamic acid content 130 g / L) at a ratio of 1 mg: 1 L. The broth was then separated using a disc centrifuge at 4000 rpm for 5 min. The supernatant was collected and then ultrafiltered through an ultrafiltration membrane (molecular weight cutoff of 1000 Da). The filtrate was collected and concentrated using a plate evaporator at a concentration temperature of 84 °C and a vacuum of -0.06 MPa. The filtrate was concentrated 3.5 times to obtain a concentrated solution, which was then transferred to a primary isoelectric tank. The pH of the concentrated solution was then adjusted to the isoelectric point of glutamic acid, 3.2, using concentrated sulfuric acid. The solution was then gradually cooled at a rate of 4 °C / h until the temperature reached 20 °C. The liquid, after passing through the primary isoelectric point tank, then passes through the secondary isoelectric point tank, where the liquid is gradually cooled at a rate of 2℃ / h until it reaches 10℃, with the pH controlled at 3.2. It is then centrifuged using a horizontal screw centrifuge at 1200 rpm for 8 minutes to separate wet glutamic acid crystals. These crystals are then dried at low temperature to obtain glutamic acid crystals. A 10% sodium carbonate aqueous solution is added to the glutamic acid crystals to dissolve and neutralize them at 60℃ and pH 6.5. The crystals are then evaporated and crystallized, and the monosodium glutamate (MSG) is separated by centrifugation and dried to obtain the final product. The resulting MSG product has a white appearance, excellent gloss, uniform particle size, and a purity of over 99.5%.

[0033] Comparative Example 1

[0034] The glutamic acid fermentation broth was centrifuged at 5000 rpm for 3 minutes using a disc centrifuge. The supernatant was collected and then ultrafiltered through an ultrafiltration membrane (molecular weight cutoff of 1000 Da). The filtrate was collected and concentrated using a plate evaporator at a concentration temperature of 80℃ and a vacuum of -0.06 MPa, resulting in a 3-fold concentration. The concentrated solution was then transferred to a primary isoelectric point tank. The pH of the concentrated solution was adjusted to the isoelectric point of glutamic acid (3.2) using concentrated sulfuric acid, and the solution was gradually cooled at a rate of 4℃ / h until the temperature reached 20℃. The liquid from the primary isoelectric point tank then passed through a secondary isoelectric point tank. The liquid was heated in a tank and gradually cooled at a rate of 2℃ / h until it reached 10℃, with the pH controlled at 3.2. Then, a horizontal screw centrifuge was used for centrifugation at 1000 rpm for 10 minutes to separate wet glutamic acid crystals. These crystals were then dried at low temperature to obtain glutamic acid crystals. A 10% sodium carbonate aqueous solution was added to the glutamic acid crystals to dissolve and neutralize them at 60℃ and pH 6.5. The crystals were then evaporated and crystallized, and the monosodium glutamate (MSG) was separated by centrifugation and dried to obtain the final product. The resulting MSG product was white in appearance, had poor gloss, and uneven particle size, with a purity of 97-98%.

[0035] Comparative Example 2

[0036] The glutamic acid fermentation broth (glutamic acid content 130 g / L) was centrifuged at 5000 rpm for 3 minutes using a disc centrifuge. The supernatant was collected, and then ultrafiltered through an ultrafiltration membrane (molecular weight cutoff of 1000 Da). The filtrate was collected and concentrated using a plate evaporator at a concentration temperature of 80℃ and a vacuum of -0.06 MPa, concentrating it 3 times to obtain a concentrated solution. Para-aminobenzoic acid was added at a rate of 1 mg per L of fermentation broth, and the solution was transferred to a primary isoelectric tank. The pH of the concentrated solution was then adjusted to the isoelectric point of glutamic acid (3.2) using concentrated sulfuric acid. The solution was then gradually cooled at a rate of 4℃ / h until the temperature reached 20℃. The liquid from the primary isoelectric point tank then passes through a secondary isoelectric point tank, with the liquid gradually cooled at a rate of 2℃ / h until it reaches 10℃, and the pH is controlled at 3.2. It is then centrifuged using a horizontal screw centrifuge at 1000 rpm for 10 minutes to separate wet glutamic acid crystals, which are then dried at low temperature to obtain glutamic acid crystals. A 10% sodium carbonate aqueous solution is added to the glutamic acid crystals to dissolve and neutralize them at 60℃ and pH 6.5. The crystals are then evaporated and crystallized, and the monosodium glutamate (MSG) is separated by centrifugation and dried to obtain the final product. The resulting MSG product is white in appearance, has moderate gloss, relatively uniform particle size, and a purity of 97-98%.

[0037] Comparative Example 3

[0038] The glutamic acid fermentation broth (glutamic acid content 130 g / L) was centrifuged at 5000 rpm for 3 minutes using a disc centrifuge. The supernatant was collected, and then ultrafiltered through an ultrafiltration membrane (molecular weight cutoff of 1000 Da). The filtrate was collected and concentrated using a plate evaporator at a concentration temperature of 80℃ and a vacuum of -0.06 MPa, concentrating the filtrate three times to obtain a concentrated solution. This concentrated solution was then transferred to a primary isoelectric point tank. The pH of the concentrated solution was adjusted to the isoelectric point of glutamic acid (3.2) using concentrated sulfuric acid, and the solution was gradually cooled at a rate of 4℃ / h until the temperature reached 20℃. Para-aminobenzoic acid was added to the liquid in the primary isoelectric point tank at a rate of 1 mg / L of fermentation broth. Add p-aminobenzoic acid in mg amounts, then pass the mixture through a two-stage isoelectric point tank while gradually cooling the solution at a rate of 2℃ / h until the temperature reaches 10℃ and the pH is controlled at 3.2. Centrifuge using a horizontal screw centrifuge at 1000 rpm for 10 minutes to separate wet glutamic acid crystals. Dry the crystals at low temperature to obtain glutamic acid crystals. Add a 10% sodium carbonate aqueous solution to the glutamic acid crystals to dissolve and neutralize them at 60℃ and pH 6.5. Then evaporate and crystallize the mixture, centrifuge to separate the monosodium glutamate (MSG), and dry to obtain the final product. The resulting MSG product is white in appearance, has good gloss, uniform particle size, and a purity of 97-98%.

[0039] Example 3

[0040] Taking Example 1 as an example, the effect of the amount of p-aminobenzoic acid added on the glutamic acid crystal product was studied.

[0041] Para-aminobenzoic acid was used as an additive component and tested separately. After repeated experiments without any abnormalities, the dosage of para-aminobenzoic acid was determined and the optimal dosage was found to ensure that the production process met the target requirements.

[0042] Crystal form determination: Crystal form was characterized by powder X-ray diffraction (PXRD).

[0043] Purity test: All groups were from the same batch of fermentation broth, with a volume of 1 ton and a glutamic acid content of 130 g / L. The purity of the products was determined by HPLC.

[0044] See Table 1 for details.

[0045] Table 1

[0046]

[0047]

[0048] As shown in Table 1 above, the purity of glutamic acid crystals increased significantly with the increase of the amount of aminobenzoic acid added compared to the group without addition. However, at the addition amount of 0.5 mg, polymorphs were still obtained. Increasing the amount of aminobenzoic acid added to 1 mg increased the purity accordingly, and the crystallized product was α crystal. Continuing to increase the amount of aminobenzoic acid added to 3 mg, on the contrary, led to a decrease in the purity of glutamic acid crystals.

[0049] Example 4

[0050] The physicochemical properties of the glutamic acid crystal products of Comparative Examples 1-2 and Comparative Examples 1-3 were compared.

[0051] Crystal form determination: Crystal form was characterized by powder X-ray diffraction (PXRD).

[0052] Yield and purity testing: All groups used the same batch of fermentation broth, with a volume of 1 ton and a glutamic acid content of 130 g / L. Product purity was determined by HPLC, and the yield was calculated based on the purity of the glutamic acid crystals and the product weight. See Table 2 for details.

[0053] Table 2

[0054]

[0055] As shown in Table 2 above, the addition of p-aminobenzoic acid in the initial stage of glutamic acid fermentation broth separation and purification effectively prevents the formation of β-shaped crystals. However, the effect of adding p-aminobenzoic acid in the concentrated solution or isoelectric solution (Comparative Examples 2-3) is not good. This may be because some primary crystal nuclei and a small amount of β-shaped crystals are generated in the early stage, resulting in small glutamic acid crystals that are difficult to separate later. During the crystallization process, p-aminobenzoic acid can be adsorbed onto the crystal surface and enter the crystal interior, affecting glutamic acid crystallization. P-aminobenzoic acid has a stronger inhibitory effect on β-shaped crystals, allowing the broth to crystallize so that only α-shaped crystals precipitate, without transforming into β-shaped crystals. The present invention also found that adding p-aminobenzoic acid can reduce the probability of clogging in the isoelectric crystallizer, thereby improving the product yield. Compared with Comparative Example 1, the glutamic acid crystals obtained in Examples 1-2 are all α-shaped crystals with high purity and a certain degree of yield improvement.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the disclosed technical content without departing from the scope of the technical solution of the present invention, resulting in equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A process for improving monosodium glutamate (MSG) crystallization using forced concentration, characterized in that, The process includes the following steps: Step 1) Centrifugation: Add p-aminobenzoic acid to the glutamic acid fermentation broth, then centrifuge using a disc centrifuge and collect the supernatant liquid; Step 2) Ultrafiltration: Ultrafiltration is performed using an ultrafiltration membrane, and the filtrate is collected; Step 3) Forced concentration: The filtrate is concentrated using a plate double-effect evaporator to obtain a concentrated solution; Step 4) Isoelectric crystallization: The concentrate enters the primary isoelectric tank, and then the pH of the concentrate is adjusted to the isoelectric point of glutamic acid, 3.2, using concentrated sulfuric acid. The liquid is then gradually cooled at a rate of 4℃ / h until the temperature reaches 20℃. The liquid from the primary isoelectric tank then passes through the secondary isoelectric tank, where it is gradually cooled at a rate of 2℃ / h until the temperature reaches 10℃, with the pH controlled at 3.

2. Finally, the liquid is centrifuged using a horizontal screw centrifuge to separate wet glutamic acid crystals, which are then dried at low temperature to obtain glutamic acid crystals. Step 5) Neutralization: Add sodium carbonate aqueous solution to the glutamic acid crystals to dissolve and neutralize them. The neutralization temperature is controlled at 60℃ and the pH value is controlled at 6.

5. Step 6) Separate monosodium glutamate: Evaporate to crystallize, centrifuge to separate monosodium glutamate, and dry to obtain the final product; The amount of para-aminobenzoic acid added is 1-2 mg per liter of glutamic acid fermentation broth, and the glutamic acid content in the glutamic acid fermentation broth is 130 g / L.

2. The process according to claim 1, characterized in that, The disc centrifuge separates the particles at a speed of 5000 rpm for 3 minutes.

3. The process according to claim 1, characterized in that, The ultrafiltration membrane has a molecular weight cutoff of 1000 Da.

4. The process according to claim 1, characterized in that, The concentration parameters are: concentration temperature of 80℃, vacuum degree of -0.06MPa, and concentration of 3-4 times.

5. The process according to claim 1, characterized in that, The centrifuge has a centrifugation rate of 500-1500 rpm and a centrifugation time of 5-10 min.

6. The process according to claim 1, characterized in that, The sodium carbonate aqueous solution has a mass fraction of 10%.

Images