Screening of Bacillus stubilis PGAN-12 and production of γ-polyglutamic acid by fermantation

Strain PGAN-12 which could produce γ-polyglutamic acid (γ-PGA) was isolated from soils and identified taxonomically as Bacillus subtilis. PGAN-12 could produce a large amount of γ-PGA in the medium containing glucose and sodium glutamate. The suitable carbon source was glucose, however, when organic acids in TCA cycle including citric acid were used as carbon sources, PGAN-12 did not produce γ-PGA. The optimum nitrogen source was yeast extract. PGAN-12 is a γ-PGA producing strain depending on L-glutamic acid in the medium. In the presence of 70 g/L sodium glutamate, the highest γ-PGA concentration reached up to 18.32 g/L, while 30 g/L sodium glutamate was added, 14.2 g/L γ-PGA was obtained with the highest yield of 62.1%.