Optimization of culture conditions for producing poly(γ-glutamic acid) by mixed fermentation

The effects of mixed fermentation conditions on production of poly(γ-glutamic acid)(γ-PGA) were investigated in a 10 L fermentor.The result showed that the temperature was an important factor for the γ-PGA production.With the temperature adjusting from 32 ℃ to 37 ℃ at 6 h in the process of cultivation,the γ-PGA production was enhanced.Furthermore,the experiments of optimizing inoculation volume of Corynebacterium glutamicum and Bacillus subtilis,pH and dissolved oxygen were performed to increase the γ-PGA production.The higher γ-PGA production was obtained when the inoculation volume of C.glutamicum and B.subtilis,pH and dissolved oxygen were adjusted to 5%,0.5%,7.0,and 20%,respectively.Under the optimal culture conditions,a final γ-PGA concentration of 38.3 g/L was obtained after 32 h fermentation.