Optimization of surfactin production by Bacillus subtilis HSO121 through Plackett-Burman and response surface method

Bacillus subtilis HSO121 was previously isolated from the formation water of an oil field and found to produce surfactin lipopeptides. Effects of 10 different components on surfactin production have been studied by Plackett- Burman design (PBD). Each component was screened on the basis of P-value, which was at 92% or above of confidence level. In PBD, significant factors influencing the surfactin production were selected for further optimization via response surface methodology approach (RSM). Four significant variables (calcium chloride, ferrous sulfate, maltose, and L-arginine) were selected for the optimization studies, and constructed via central composite design (CCD). Calcium chloride, maltose and L-arginine showed a significant positive effect on surfactin production, while ferrous sulfate had no significant effect. An overall 38.06-fold increase in surfactin production yield was achieved in the optimized medium as compared with the unoptimized basal medium. Surfactin production yield increased significantly with optimized medium (47.58 g/l) when compared with the unoptimized one (1.25 g/l).