Efficient preparation of extremely high-purity surfactin from fermentation broth by ethanol extraction

It is challenging to cost-effectively obtain analytically pure surfactin from fermentation broth for value-added applications. In this study, a newly efficient extraction process with ethanol was developed for preparation of high-purity surfactin from fermentation broth produced by Bacillus subtilis ATCC 21332. The residual of acid in the surfactin precipitation before extraction was found to be a significant factor in the separation performance, and an extremely high purity of 98% and recovery of over 90% was obtained after optimization. The surfactin isolated by ethanol extraction contained fewer impurities than that prepared by dichloromethane extraction which is commonly employed. The difference in the impurities present appears to be due to the fact that surfactin is unable to form micelles when presented in ethanol in comparison to dichloromethane. Moreover, the use of ethanol to extract surfactin from an dichloromethane extract can further furnish analytically pure surfactin. The present extraction process employs an environmentally-friendly solvent, and has excellent separation performance enabling the isolation of surfactin for high added-value applications.