Fed-batch fermentation of citrus Peel using Bacillus subtilis for producing surfactin

초록

Surfactin produced in Bacillus is an industrial material as a biosurfactant. However, surfactin induces the sporulation of Bacillus, leading to limitations in mass production. This study is about a fed-batch process development that produces surfactin through Bacillus subtilis feeding with citrus peels as biomass. A system for physically removing surfactin foam during Bacillus cultivation was developed, where the medium was replenished in a fed-batch type based on the amount of venting out. The method of supplementing only glucose or citrus peels could not maintain cell activity for long and led to inactivity, while supplementing both glucose and citrus peels together kept the cells active for over 40 h allowing continuous surfactin production. As a result of applying citrus peel to the inoculation media, Bacillus cultured in citrus peel-free media for fermentation seed underwent a longer lag phase in adapting to the new environment, which led to a further delay in surfactin synthesis. Eventually, the optimized bioprocess allowed to produce 53% more surfactin while incubating for four times longer than the fed-batch type using glucose only. The results of this study represent important development for the future utilization of citrus peel biomass processing, as it optimizes the fed-batch process for surfactin production through Bacillus fermentation of citrus peel.

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