Utilization Of Glutamic Acid Fermentative Waste Microbial Biomass

The waste microbial biomass produced by glutamic acid fermentation is one of the by-products in the production of monosodium glutamate.The million tons of the monosodium glutamate waste biomass are produced every year in China,which contains about 70 percent of the crude protein.In the past,the waste water of fermented mycelium was directly discharged into the surface water bodies,which caused environmental pollution and the waste of protein resources.The feasibility of using the hydrolysate of waste microbial biomass from glutamate fermentation as a nitrogen source for?-polyglutamic acid fermentation was investigated.Hydrolysis of the waste microbial biomass was firstly optimized with protein hydrolysability and solubility as indictors.The optimal hydrolysis conditions were achieved by orthogonal experimental design with chemical,biological,physical and combined methods.The chemical-biochemical combined method led to a protein hydrolysabilty of 47.18%and solubility of 94.09%.With this method,chemical hydrolysis was firstly conducted at 110°C for 12 h with a substrate to liquid ratio of 1:0.5 and a hydrochloric concentration of 3mol?L^-1,followed by enzymatic hydrolysis at 55°C for 8 h at pH 4.0 and an acidic protease loading of 2.5%?on substrate?.Under the same nitrogen concentration,the hydrolysate and yeast extract were mixed at different ratios and used as a nitrogen source for?-polyglutamic acid fermentation.The results show that it is feasible to use the hydrolysate of waste microbial biomass prepared at the optimal hydrolysis conditions as the nitrogen source for?-polyglutamic acid fermentation.