Foam-free production of Surfactin via anaerobic fermentation of Bacillus subtilis DSM 10^sup T

Surfactin is one of the most popular biosurfactants due to its numerous potential applications. The usually aerobic production via fermentation of Bacillus subtilis is accompanied by vigorous foaming which leads to complex constructions and great expense. Therefore it is reasonable to search for alternative foam-free production processes. The current study introduces a novel approach to produce Surfactin in a foam-free process applying a strictly anaerobic bioreactor cultivation. The process was performed several times with different glucose concentrations in mineral salt medium. The fermentations were analyzed regarding specific (q^sub Surfactin^, vol. q^sub Surfactin^) and overall product yields (Y^sub P/X^, Y^sub P/S^) as well as substrate utilization (Y^sub X/S^). Fermentations in which 2.5 g/L glucose were employed proofed to be the most effective, reaching product yields of Y^sub P/X^=0.278 g/g. Most interesting, the product yields exceeded classical aerobic fermentations, in which foam fractionation was applied. Additionally, values for specific production rate q^sub Surfactin^ (0.005 g/(g--h)) and product yield per consumed substrate (Y^sub P/S^=0.033 g/g) surpass results of comparable foam-free processes. The current study introduces an alternative to produce a biosurfactant that overcomes the challenges of severe foaming and need for additional constructions.