Enhancement of Surfactin yield by improving the medium composition and fermentation process

Surfactin is one of the most promising biosurfactants due to its extraordinary surface activity. Commonly, the well-established Cooper medium, a glucose-based mineral salt medium, is utilized for the microbial production of Surfactin. The current study investigated the enhancement of Surfactin yields by analyzing the effects of different glucose concentrations, next to the introduction of an alternative chelating agent and nitrogen source. The utilization of 8 g/L glucose, 0.008 mM Na3citrate and 50 mM (NH4)2SO4 increased Surfactin yields from 0.7 to 1.1 g/L during shake flask experiments applying Bacillus subtilis DSM10(T). Consequentially conducted shake flask experiments, employing five other Surfactin producer strains during cultivation in the former and enhanced version of the Cooper medium, suggest a general enhancement of Surfactin yields during application of the enhanced version of the Cooper medium. The enhancement of the medium composition is therefore most likely independent from the employed producer strain. The following utilization of the enhanced medium composition during fed-batch fermentation with integrated foam fractionation yielded 30 % more Surfactin in comparison to batch fermentations with integrated foam fractionation employing the former version of the Cooper medium.