Isolation of biosurfactant-producing bacteria from the Caspian Sea and determination of their biosurfactant activity

Abstract

Background: Biosurfactants are unique amphipathic molecules with extensive application in removing organic and metal contaminants. The purpose of this study was to isolate the biosurfactant-producing bacteria and characterize the surface-active properties of the metabolites produced.Materials and Methods: This study was conducted in three Caspian Sea coastal regions in Babolsar during 2007-8. In primary screening, hemolytic and emulsifying activities were performed on blood agar plates and in culture medium, respectively and then the reduction in the surface tension, as a biosurfactant-producing index, was determined quantitatively by captive drop cell instrument. The isolated strain was also investigated for its ability to use different hydrocarbon pollutants using the surface tension measurement.Results: One out of 10 different strains exhibited high ability to produce biosurfactant. This strain called Caspian petroleum A1 (CPA1). Biochemical tests showed that CPA1 classified in aerobic gram-negative cocci, neisseriaceae family and acinetobacter genus. CPA1 utilized crude oil and gasoline, as carbon and energy sources, to reduce the surface tension of culture medium from 71 to 42 and 39 mN/m. Conclusion: CPA1, as a biosurfactant-producer, was isolated and identified based on potential for biodegradation of hydrocarbon pollutants (e.g. crude oil, gasoline, anthracen and naphthalene)