At present, freezing isoelectric point ion exchange method is generally used for extraction. The fermentation broth is slowly stirred and cooled to 5℃ with frozen brine in an equipotential tank, and the Ph value is adjusted to 3.22 (isoelectric point) with sulfuric acid; After 8 hours of precipitation, crude glutamic acid was obtained by centrifugal separation. The mother liquor and supernatant were mixed and exchanged with ion exchange resin, and eluted with ammonia water.
The former part flows into the supernatant and then returns to the column. The latter part is used as eluent together with ammonia water, and the higher part is returned to the equipotential tank together with fermentation broth. Adding glutamic acid into a neutralization tank with bottom water at 60-65℃, stirring, slowly adding soda solution to neutralize until the Ph value is 6.2-6.4, and controlling the concentration of the neutralization solution at the relative density of1.1.7-1.1.08 (2/kloc
When that neutralize solution is cooled to below 50 DEG C, an appropriate amount of sodium sulfide solution is adde to remove iron; Then adjust the Ph value to 6.2 ~ 6.4 with crude glutamic acid, and raise the temperature to 60℃, then add powdered activated carbon, stir for half an hour, and then send it to a filter press for pressure filtration.
Step two, decolorizing the filtrate with granular activated carbon column to obtain clear liquid; The clear liquid was sent to a vacuum crystal boiling tank and evaporated and concentrated at 60 ~ 70℃ until the relative density was 1.28(3 1.5084). After adding 0.3 6~0.542mm seed crystal, the crystal continued to evaporate and crystallize. During this period, it is necessary to kill the crystal with hot water and add a certain amount of clear liquid.
After discharging, the crystal monosodium glutamate is obtained by centrifugal separation in a crystal growth tank, and the mother liquor is evaporated and crystallized after decoloration. The refining yield can reach 92% of the theoretical amount.
Extended data
1, flavoring agent
When used as flavoring agent, the general dosage is 0.2% ~ 0.5%. Besides being used alone, it should also be mixed with nucleic acid seasonings such as nucleotide and inosine sodium to make compound seasoning, so as to improve the effect. Sodium glutamate is the most widely used preservative at home and abroad. When it is stored with salt, it can enhance its taste. When it is used with 5'- inosine sodium or 5'- guanosine sodium, it has a multiplier effect.
Sodium glutamate has a strong meat flavor, and monosodium glutamate can still feel the flavor when diluted to 3000 times with water, which is widely used in family, catering industry and food processing industry (soup, sausage, fish cake, spicy soy sauce, canned food, etc. ). When sodium guanosine and sodium glutamate are used at the same time, there is a synergistic effect, which can improve the umami taste. It is also called fresh-keeping additive or strong monosodium glutamate.
2. Medical biochemical reagents
Glutamate is widely distributed in animals and plants and is a natural nutrient in food. After eating glutamic acid, 96% is absorbed by the body, and the rest is excreted with urine after oxidation.
Although glutamic acid is not an essential amino acid for human body, it can transfer amino groups with ketoacids in nitrogen metabolism and synthesize other amino acids. Glutamate can reduce toxins in the blood. When liver function is damaged, the ammonia content in blood increases, causing serious nitrogen metabolism disorder and leading to hepatic coma. Glutamate can interact with ammonia and reduce the ammonia content in blood.
In addition, brain tissue can only oxidize glutamic acid, but not other amino acids. Glutamine can play an energy role in brain tissue when glucose supply is insufficient, so glutamic acid is necessary to improve and maintain brain function. In addition, it can be used to prevent hepatic coma and epilepsy in medicine, and can also be used as a brain nutrient.
3, organic synthesis intermediates
It can be used as an intermediate of organic synthesis in industry, but it accounts for a very small proportion in the world annual output, such as additives, osmotic membranes, silk protein modification, leather additives, biomedical materials, modified regenerated collagen fibers and other fields.
Reference source Baidu Encyclopedia-Sodium Glutamate