The fermentative production of biosurfactants by Bacillus subtilis strain B30 and the evaluation of biosurfactant based enhanced oil recovery using core-flood were investigated. Different carbon sources (glucose, sucrose, starch, date molasses, cane molasses) were tested to determine the optimal biosurfactant production. The isolate B30 produced a biosurfactant that could reduce the surface tension and interfacial tension to 26.63±0.45 mN/m and 3.79±0.27 mN/m, respectively in less than 12h in both glucose or date molasses based media. A crude biosurfactant concentration of 0.3-0.5 g/l and critical micelle dilution (CMD) values of 1:8 were observed. The biosurfactants gave stable emulsions with wide range of hydrocarbons including light and heavy crude oil. The biosurfactants were partially purified and identified as a mixture of lipopeptides similar to surfactin, using high performance thin layer chromatography and Fourier transform infrared spectroscopy. The biosurfactants were stable over wide range of pH, salinity and temperatures. The crude biosurfactant preparation enhanced light oil recovery by 17-26% and heavy oil recovery by 31% in core-flood studies. The results are indicative of the potential of the strain for the development of ex situ microbial enhanced oil recovery processes using glucose or date molasses based minimal media.
Keywords: Bacillus subtilis; Biosurfactant; Critical micelle dilution; Emulsification index; Microbial enhanced oil recovery; Surface and interfacial tension reduction.
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