Optimization of γ-Polyglutamic Acid Production by Bacillus licheniformis P-104
ZHANG Ye-wei1, WEI Xue-tuan1,2, HU Zhong-bo1, LUO Ming-fang3, XU Lin1,2, LIU Hui-zhou2 (1. Graduate University of Chinese Academy of Sciences, Beijing 100049, China; 2. Inst. Process Eng., CAS, Beijing 100190, China; 3. Inst. Microbiol., CAS, Beijing 100101, China)
The fermentation conditions for γ-polyglutamic acid (γ-PGA) production with Bacillus licheniformis P-104 were optimized in flasks, and the mesoscale batch fermentation was performed in a 6.6 L fermentor. The results showed that high yield of g-PGA with ultra high molecular weight (over 2500 kDa) was obtained under the optimal conditions (g/L): glucose 80, sodium glutamate 70, sodium citrate 10, (NH4)2SO4 10, MnSO4 0.15, MgSO4 0.8, K2HPO4 0.6, NaNO3 4, inoculation time 8 h, inoculum amount 3%(ψ), initial pH value 7.5, 37℃, and 180 r/min. In the flask fermentation, the maximum γ-PGA yield reached 44.7 g/L for 24 h, and the highest specific productivity was 1.49 g/(L·h), being twice of the ultra high molecular weight γ-PGA reported previously. In a 6.6 L fermentor, 32 g/L γ-PGA was obtained for 33 h with a specific productivity of 0.97 g/(L·h).