Reducing Impurities in Fermentation Broth for γ-Polyglutamic Acid Production by Medium Optimization Using Bacillus licheniformis CGMCC 3336

In this paper, the fermentation medium was optimized for the production of poly-(gamma-glutamic acid) and reducing impurities in the fermentation broth using Bacillus licheniformis CGMCC3336. The results indicated that choline chloride, pyridoxine, arginine, glutamine, and methionine could effectively enhance gamma-PGA production, individually. Especially, when 0.2 g/L methionine was added, the gamma-PGA production was increased by onefold compared to the control. Flask fermentation was carried out using the optimized medium a 12.0 g/L gamma-PGA was accumulated in the fermentation broth which was increased by three folds as compared to the control. Using the optimized medium a 30.3 g/L gamma-PGA was accumulated in the fermentation broth in a 5 L bioreactor and impurities in the fermentation broth was reduced apparently. The results suggested that, choline chloride, pyridoxine, arginine, glutamine, and combined with methionine had the same effect on gamma-PGA production as yeast extract.