Production of poly-γ-glutamic acid by submerged fermentation with Bacillus subtilis natto

Production of poly-γ-glutamic acid (γ-PGA) by cultivation of Bacillus subtilis natto CICC 20643 in submerged state had been studied.The optimum cultivation conditions through single factor and orthogonal experiments were set as follows:sucrose 25g/L, yeast extract 5g/L, glutamic acid 40g/L, initial pH at 6.5, culture volume 70mL in 250mL conical flask.Under the optimum cultivation conditions, B.subtilis natto was shaking cultivated at 37℃, 120r/min for 24h, then 5%NaCl was added, and subsequently cultivated for another 24h.As a result, the yield ofγ-PGA was got at 18.04g/L.The experimental result showed that B.subtilis natto CICC 20643 was a strain of high-yieldγ-PGA and addition of NaCl in the course of cultivation could increase the yield ofγ-PGA.