谷氨酸发酵废菌体的水解与替代酵母膏生产多聚谷氨酸

为研究谷氨酸发酵废菌体水解液用作培养基氮源的可行性，以蛋白质水解度和溶解度为衡量指标，采用化学、生物、物理以及这几种方法的联合处理，通过正交优化实验，得出了菌体蛋白水解的最佳工艺条件为化学-生物联合处理，在盐酸浓度3 mol·L-1、温度110 ℃、料液比1:0.5、水解12 h后使用酸性蛋白酶酶解，调节料液pH为4、酶底比2.5%、温度55 ℃、酶解8 h，水解完成后蛋白质水解度达到47.18%，溶解度达到94.09%。在总氮相等的情况下，将水解液和酵母膏以不同的比例组合，替代正常发酵产γ-聚谷氨酸过程的氮源。结果表明谷氨酸发酵废菌体经过最佳工艺水解后，其水解液可以用作发酵产γ-聚谷氨酸的氮源。

Hydrolysis of glutamic acid fermented waste bacteria and substitution of yeast extract for production of polyglutamic acid

The feasibility of using the hydrolysate of waste microbial biomass from glutamate fermentation as a nitrogen source for γ-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 3 mol·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 γ-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 γ-polyglutamic acid fermentation.