Enhanced Production of Poly-γ-glutamic Acid by Bacillus licheniformis TISTR 1010 with Environmental Controls

Bacillus licheniformis TISTR 1010 was used for glutamic acid-independent production of poly-gamma-glutamic acid (gamma-PGA). A fed-batch production strategy was developed involving feedings of glucose, citric acid, and ammonium chloride at specified stages of the fermentation. With the dissolved oxygen concentration controlled at >= 50% of air saturation and the pH controlled at similar to 7.4, the fed-batch operation at 37 degrees C afforded a peak gamma-PGA concentration of 39.9 +/- 0.3 g L-1 with a productivity of 0.926 +/- 0.006 g L-1 h(-1). The observed productivity was nearly threefold greater than previously reported for glutamic acid-independent production using the strain TISTR 1010. The molecular weight of gamma-PGA was in the approximate range of 60 to 135 kDa.