Abstract

Biosurfactants are biodegradable, non-toxic and ecofriendly compounds released by microorganisms. Most of the microorganisms were isolated from contaminated sites by petroleum hydrocarbon and industrial wastes. In this study, a biosurfactant-producing strain was isolated from Daqing oil-contaminated sites in China by enrichment culture, hemolytic activity assay, hydrolyzing oil activity assay, improved degreasing effect assay, and emulsification activity measurement. The strain was identified as Pseudomonas sp. BS1 based on its physiological characteristics and analysis of its 16S rRNA gene sequence. The identified isolate is capable of producing glycolipids or other anionic surfactants as determined in our analysis of a phenotypic assay using CTAB. The biosurfactant was isolated from the culture supernatant and identified as dirhamnolipids (Rha-Rha-C₁₀-C₁₀) by high-performance liquid chromatography–mass spectrometry. The culture filtrate and cell-free supernatant produced by this isolate were found to be highly effective in oil displacement from oil sand, suggesting that the isolate has potential use in enhanced oil recovery.

Key words: Biosurfactant, Pseudomonas sp., dirhamnolipids, microbial enhanced oil recovery.