Isolation and identification of surfactin producing Bacillus Subtilis strain and its effect of surfactin on crude oil

Abstract:

Strains producing biological surfactants were isolated from formation water of Daqing oil field, Heilongjiang Province, China. From which a lipopeptide producing strain ZW-3 was screened out by PCR of the sfp gene. The mor-phology ,cultural characteristics ,physiological , biochemical properties and chemotaxonomy of strain ZW-3 were studied. The strain is rod shaped (0.7～0.8 mm×2~3 mm) , gram-positive, spore-forming and aerobic bacteria. Its (G+C) content was determined to be 42.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequence demonstrated that it was closely related to the genus Bacillus subtilis, and the metabolites of strain ZW-3 was analyzed by thin layer chromatog-raphy and high performance liquid chromatography, the result indicated that the biosurfactant strain ZW-3 produced was surfactin. It could reduce surface tension of bacterial fermentation culture medium and water/oil- interfacial tension from 68.82 mN/m to 24.88 mN/m and from 23.53 mN/m to 4.57 mN/m ,respectively, and its mixture with 1.8%NaOH could reduce water/oil- interfacial tension to an ultra low level (1.2×10-3mN/m), Its critical micelle concentration (CMC) was tested to be 33.3 mg/L(3.24×10-5 mol/L)at 25℃, and it had excellent emulsifying(2.89U) and foaming property. All these results showed that this biosurfactant had great potential in pharmaceutics, environmental protection, cosmetic, oil recov-ery and many other application fields.