Study of the biosurfactant-producing profile in a newly isolated Rhodococcus ruber strain

Abstract

A biosurfactant-producing strain Z25 was isolated from the oil production water in Daqing Oilfield, China. The strain was identified as Rhodococcus ruber by 16S rDNA sequencing. Rhodococcus ruber Z25 showed a preference of alkanes as carbon sources for biosurfactant synthesis. The optimal biosurfactant production was achieved at the NaCl concentration of 2.5% at 34 °C. In batch cultivation, R. ruber Z25 exhibited a cell-growth associated biosurfactant-producing process on n-hexadecane and the maximum yield of biosurfactant production was 13.34 g/L at 44 h. The rate of biosurfactant production per unit biomass (R(biosurf/biomass)) was used to characterize the biosurfactant-producing profile. A two-stage biosurfactant-producing profile of R. ruber Z25 was established by the R (biosurf/biomass) curve, exhibiting the biosurfactant production in correlation with cellular hydrophobicity and biomass accumulation. The crude biosurfactant was extracted by methyl tert-butyl ether (MTBE) method and only one glycolipid fraction at Rf value of 0.64 was detected by thin layer chromatography (TLC) analysis.