Abstract: In this study, Bacillus subtilis was cultivated in a 5-liter fermentor to produce byγ-PGA by two different fermentation processes: batch fermentation and fed-batch fermentation. The results showed that increasing the agitation speed from 150 to 250 r/min could bring the yield ofγ-PGA to 30.86 g/L from 11.30 g/L in batch fermentation under ventilation conditions. Ventilation conditions and agitation at 250 r/min were also used in the fed-batch fermentation, and 50 mL of 200 g/L glucose was fed at a time when glucose concentration in fermentation broth was lower than 20 g/L, increasing the yield of γ-PGA to 52.20 g/L.

Key words: Bacillus subtilis, agitation, batch fermentation, fed-batch fermentation, γ-PGA