Isolation of halotolerant Bacillus licheniformis WX-02 and regulatory effects of sodium chloride on yield and molecular sizes of poly-gamma-glutamic acid.

A poly-gamma-glutamic acid (gamma-PGA) productive strain, halotolerant bacterium WX-02 was isolated from the saline soil of China (Yingcheng). By physiological, biochemical, and 16S rDNA sequence analysis methods, the strain was identified as Bacillus licheniformis. The effect of NaCl concentration on gamma-PGA production by WX-02 was investigated in modified E (ME) medium. It was found that the gamma-PGA production was salt-inducible, and the highest volumetric yield of gamma-PGA (13.86 g/l) was attained with 8% of NaCl. It was also observed that the molecular size of gamma-PGA decreased when the NaCl concentration increased. This was the first report of isolation and identification of a gamma-PGA productive strain, halotolerant B. licheniformis. This study provided a simple strategy for controlling the yield and molecular size of gamma-PGA by WX-02.