Enhancement of hydrocarbon wastebiodegradation by addition of a biosurfactantfrom Bacillus subtilis O9

A non-sterile biosurfactant preparation (surfactin)was obtained from a 24-h culture of Bacillussubtilis O9 grown on sucrose and used to study itseffect on the biodegradation of hydrocarbon wastes byan indigenous microbial community at theErlenmeyer-flask scale. Crude biosurfactant was addedto the cultures to obtain concentrations above andbelow the critical micelle concentration (CMC). Lowerconcentration affected neither biodegradation normicrobial growth. Higher concentration gave highercell concentrations. Biodegradation of aliphatichydrocarbons increased from 20.9 to 35.5% and in thecase of aromatic hydrocarbons from nil to 41%,compared to the culture without biosurfactant. Theenhancement effect of biosurfactant addition was morenoticeable in the case of long chain alkanes. Pristaneand phytane isoprenoids were degraded to the sameextent as n-C17 and n-C18 alkanes and, consequently,no decrease in the ratios n-C17/pri and n-C18/phy wasobserved. Rapid production of surfactin crudepreparation could make it practical for bioremediationof ship bilge wastes.