Characterization of new biosurfactant produced by Klebsiella sp Y6-1 isolated from waste soybean oil

To obtain predominant bacteria degrading crude oil, we isolated some bacteria from waste soybean oil. Isolated bacterial strain had a marked tributyrin (C-4:0) degrading activity as developed clear zone around the colony after incubation for 24 h at 37 degrees C. It was identified as Klebsiella sp. Y6-1 by analysis of 16S rRNA gene. Crude biosurfactant was extracted from the culture supernatant of Klebsiella sp. Y6-1 by organic solvent (methanol: chloroform:1-butanol) after vacuum freeze drying, and the extracted biosurfactant was purified by silica gel column chromatography. When the purified biosurfactant dropped, it formed degrading zone on crude oil plate. When a constituent element of the purified biosurfactant was analyzed by TLC and SDS-PAGE, it was composed of peptides and lipid. The emulsification activity and stability of biosurfactant was measured by using hydrocarbons and crude oil. The emulsification activity and stability of the biosurfactant showed better than the chemically synthesized surfactant. It reduced the surface tension of water from 72 to 32 mN/m at a concentration of 40 mg/l. (c) 2007 Elsevier Ltd. All rights reserved.