Biosurfactant production by Bacillus coagulans

A new biosurfactant producer, Bacillus coagulans , was isolated from soil. Its 24‐h‐old culture broth had a low surface tension (27–29 mN/m). Optimization of cell growth of this bacterium led to maximal biosurfactant production with glucose or starch as the organic carbon source, a pH in the range 4.0–7.5, and incubation temperatures from 20 to 45°C. The crude biosurfactants obtained after neutralization and lyophilization of the acid precipitate yielded a minimal aqueous solution surface tension value of 29 mN/m and an interfacial tension value of 4.5 mN/m against hexadecane. The critical micelle concentration of the crude biosurfactants was 17 mg/L. Addition of NaCl to the aqueous solution of the crude product caused lowering of surface tension at both the aqueous solution‐air and aqueous solution‐ n ‐hexadecane interfaces. These results indicate that the biosurfactants obtained have potential environmental and industrial applications and may have uses in microbially enhanced oil recovery.