g-聚谷氨酸产生菌的筛选及发酵条件

从土壤中筛选分离到一株高产g-聚谷氨酸的菌株PGAN-12，经鉴定为枯草芽孢杆菌(Bacillus subtilis)，在含谷氨酸钠和葡萄糖的培养基中可生成大量g-聚谷氨酸，缺少谷氨酸钠和碳源均不能合成g-聚谷氨酸. PGAN-12合成g-聚谷氨酸的合适碳源为葡萄糖，而TCA循环中的有机酸包括柠檬酸均不能使PGAN-12合成g-聚谷氨酸. 最适氮源是酵母膏. PGAN-12是谷氨酸依赖型的g-聚谷氨酸产生菌，在谷氨酸钠浓度为70 g/L时，g-聚谷氨酸取得最大产量18.32 g/L，但在谷氨酸钠浓度为30 g/L时，获得了最大的表观转化率62.1%，此时生成g-聚谷氨酸为14.2 g/L.

Screening of Bacillus stubilis PGAN-12 and Production of γ-Polyglutamic Acid by Fermantation

Strain PGAN-12 which could produce ?-polyglutamic acid (?-PGA) was isolated from soils and identified taxonomically as Bacillus subtilis. PGAN-12 could produce a large amount of ?-PGA in the medium containing glucose and sodium glutamate. The suitable carbon source was glucose, however, when organic acids in TCA cycle including citric acid were used as carbon sources, PGAN-12 did not produce ?-PGA. The optimum nitrogen source was yeast extract. PGAN-12 is a ?-PGA producing strain depending on L-glutamic acid in the medium. In the presence of 70 g/Lsodium glutamate, the highest ?-PGAconcentration reached up to 18.32 g/L, while 30 g/Lsodium glutamate was added, 14.2 g/L?-PGA was obtained with the highest yield of 62.1%.