Improving Poly-(γ-Glutamic Acid) Production and Reducing Impurities in Fermentation Broth by Medium Optimization Using Bacillus. licheniformis CGMCC3336

Poly-(gamma-glutamic acid) is a naturally occurring, water-soluble polymer, which has been considered as a promising biodegradable material and there has been a great deal of interest in poly-(gamma-glutamic acid) and its derivatives in a wide range of industries. In this paper, the fermentation medium was optimized for increasing the production of poly-(gamma-glutamic acid) and reducing impurities in fermentation broth using a new mutant strain, Bacillus. ficheniformis CGMCC3336. The results indicated that glucose and yeast extract were beneficial for cell growth and poly-(gamma-glutamic acid) production. Especially, when half the yeast extract was replaced by inorganic ammonium nitrate, the production of poly-(gamma-glutamic acid) was even increased significantly (17%). In a 30 L bioreactor, more than 35 g/L of poly-(gamma-glutamic acid) could be produced in 34 h and the poly-(gamma-glutamic acid) productivity was 1.03 g/Uh. The fermentation curve also indicated that the strain was very special comparing with the previous poly-(gamma-glutamic acid) producers.