Method one (neutralization extraction and refining method)
Glutamic acid fermentation uses about 15% glucose as a carbon source, and adds an appropriate amount of inorganic salts and biotin to prepare a fermentation medium. After continuous digestion and cooling to 40°C, it is sent to a sterilized empty fermentation tank; The added liquid ammonia is the nitrogen source, and the glutamate-producing bacteria that has undergone secondary expansion culture are inoculated. The extraction method is generally frozen isoelectric-ion exchange method. The fermentation broth was slowly stirred and cooled with frozen brine in an isoelectric tank to cool down to 5°C, while adjusting the Ph value to 3.22 (isoelectric point) with sulfuric acid; after 8 hours of precipitation, the precipitate was centrifuged to obtain crude glutamic acid; mother liquor and upper layer After the clear liquid is prepared, it is exchanged with ion exchange resin and eluted with ammonia; the front fraction is merged into the supernatant and re-loaded on the column, the latter fraction is used as the eluent together with the ammonia, and the high fraction is returned to the isoelectric tank together with the fermentation broth. Add glutamic acid to a neutralization tank with 60～65℃ bottom water, stir, and slowly add soda ash solution to neutralize to a Ph value of 6.2～6.4, and control the concentration of the neutralization solution to a relative density of 1.1 7～1.18 (21 ～2 2°Bé); After the neutralization solution is cooled to below 50°C, add an appropriate amount of sodium sulfide solution to remove iron; then use crude glutamic acid to adjust the Ph value to 6.2～6.4, and heat to 60°C, then add powder Activated carbon, stirred for half an hour, then sent to a filter press for pressure filtration; then the filtrate was decolorized with a granular activated carbon column for a second time to obtain a clear liquid; the clear liquid was sent to a vacuum crystal boiling pot and evaporated and concentrated to a relative density of 1.28 (31.5084) at 60-70°C ), add 0.3 6～0.542mm seed crystals and continue to evaporate and crystallize. During this period, hot water is required to kill the crystals and add a certain amount of clear liquid; After decolorization, evaporate and crystallize, and the refining yield can reach 92% of the theoretical amount.
Method two (α-ketoglutarate synthesis method)
The first step: In the presence of NH4+ and hydrogen donor reducing coenzyme II (NADPH2), α-ketoglutarate is catalyzed by glutamate dehydrogenase (GHD) to undergo a reductive amination reaction, or transaminase ( AT) catalyzes the transamination reaction, or glutamate synthase (GS) catalyzed to form glutamate.
The second step: the glutamic acid fermentation broth and hydrochloric acid are centrifuged and stirred, crystals are grown, stirred, and precipitated to produce sodium glutamate. To
Method three (acrylonitrile synthesis method)
Under the conditions of 120~150℃ and 20~30MPa, the cobalt catalyst Co2(CO)8 locally selectively catalyzes the hydroformylation of acrylonitrile to produce 3-cyanopropionaldehyde (the yield of linear aldehyde is 80%), which is then passed through Strecker Degradation reaction) synthesis to produce sodium L-glutamate. This method used to be an industrial production process route, but was replaced by a more economical method.
