| Corn stover was pretreated and enzymatically hydrolyzed into reducing sugar to produce polyγ-glutamic acid (γ-PGA) by fermentation. The effects of glucose, xylose, L-monosodium glutamate monohydrate and metal ion on the growth of B. subtilis CGMCC 1250 and γ-PGA production were studied, and the components of the fermentation medium were optimized and fermentation was conducted in a fermenter. The results showed that corn stover was pretreated by dilute base and enzymatically hydrolyzed by compound enzyme, and mass concentration of the reducing sugar was (76.3±5.7)g/L. The hydrolysate was mainly composed by glucose and xylose, with a ratio of 2.19∶?1. Then 40 g/L of L-monosodium glutamate monohydrate, 0.29 g/L of ZnSO4·7H2O, 0.05g/L of MnSO4·7H2O and 0.11 g/L of FeCl3·6H2O were added into the initial fermentation medium, resulting into (20.5±2.70)g/L of γ-PGA. Finally, a fed-batch strategy was conducted in a 3 L fermenter to increase product yield, and 256 g/L of γ-PGA was achieved. |
