Process for producing polyglutamic acid through fermentation

The invention belongs to the technical field of biological fermentation, and discloses a process for producing polyglutamic acid by fermentation, which comprises the following steps: transferring a bacillus subtilis secondary seed solution into a fermentation culture medium according to the inoculum size of 1-5%, and culturing for 36 hours to obtain a polyglutamic acid fermentation solution; the fermentation medium comprises the following components: 40g/L of glucose, 20g/L of corn steep liquor, 10g/L of yeast extract, 50g/L of sodium glutamate, 6g/L of ammonium sulfate, 5g/L of glycerol, 4g/L of D-phenylalanine, 0.2 g/L of monopotassium phosphate, 0.2 g/L of dipotassium phosphate, 0.1 g/L of magnesium sulfate heptahydrate and 1mg/L of ferrous sulfate heptahydrate. By optimizing the components of the fermentation culture medium, the synthesis efficiency of the polyglutamic acid is improved. The glutamic acid extraction wastewater is used for replacing water for the fermentation culture medium, residual glutam