At present, both domestically and internationally, rice, starch, or molasses are used as raw materials for production through processes such as saccharification, fermentation, extraction, and refinement
(1) The saccharification of starch. The saccharification of starch is often done using a double enzyme method. Rice is soaked, sanded, or starch is directly blended into a relative density of 1.11 (14 ° B é) starch slurry, which is added at pH 4.5 and 90 ℃ α- Liquefaction of amylase for 15-20 minutes, by heating to 100 ℃ to kill the enzyme for 5 minutes; After feeding, the filter residue can be used as feed through plate and frame pressure filtration. The filtrate is adjusted to pH 5.0 and added β- Amylase is saccharified at 60 ℃ for 12 hours, then heated to 100 ℃ to kill the enzyme and cooled to clarify. The supernatant is directly placed in the sugar storage tank, and the precipitate is filtered with filter aid diatomaceous earth. The starch sugar conversion rate can reach 92%.
(2) Glutamic acid fermentation. Using about 15% glucose as the carbon source, an appropriate amount of inorganic salt and biotin were added to form a fermentation medium. After continuous digestion and cooling to 40 ℃, it was sent to a sterilized fermentation empty tank. Using the added liquid ammonia as the nitrogen source, glutamic acid producing bacteria were inoculated with secondary expanded culture. After ventilation fermentation for 30 hours, the sugar acid conversion rate could reach 50%, and the acid production level was about 7.0% -7.5%. The pH of the fermentation process is controlled between 7.0-7.2, and the temperature is controlled between 32-34 ℃ in the early stage and 34-37 ℃ in the later stage.
(3) Extraction of glutamic acid. The extraction of glutamic acid is generally carried out using the freezing isoelectric ion exchange method. The fermentation broth is slowly stirred and cooled to 5 ℃ with frozen saline water in an isoelectric tank, while the pH is adjusted to 3.22 (isoelectric point) with sulfuric acid; After 8 hours of precipitation, crude glutamic acid was obtained by centrifugation; After mixing the mother liquor and the upper clear liquor, exchange them with ion exchange resin and wash them with ammonia water; The front flow fraction is collected into the upper clear liquid and re added to the column. The rear flow fraction is used as the eluent together with ammonia, and the high flow fraction is returned to the isoelectric tank with the fermentation broth. The extraction rate can reach 88% -90%.
(4) Glutamic acid refining. Add glutamic acid to a neutralization tank containing bottom water at 60-65 ℃, stir, and slowly add a pure alkali solution to neutralize to pH 6.2-6.4. Control the concentration of the neutralization solution at a relative density of 1.17-1.18 (21-22 ° B é); Wait for the neutralization solution to cool down to below 50 ℃, add an appropriate amount of sodium sulfide solution to remove iron, then adjust the pH to 6.2-6.4 with crude glutamic acid, and raise the temperature to 60 ℃. Then, add powdered activated carbon, stir for 0.5 hours, and send it to a filter press for filtration. Then, use a granular activated carbon column to decolorize the filtrate twice to obtain a clear solution; The clear liquid is sent into a vacuum crystal boiling pot and evaporated and concentrated at 60-70 ℃ to a relative density of 1.28 (31.5 ° B é). After adding 0.36-0.542mm crystal seeds, it continues to evaporate and crystallize. During this period, hot water is used to kill the crystals and a certain amount of clear liquid is added; After feeding, crystalline monosodium glutamate is obtained by centrifugation through a crystal growth tank. The mother liquor or after decolorization, it is evaporated and crystallized, and the refining yield can reach 92% of the theoretical amount.