Biosurfactant production and oil degradation by Bacillus siamensis and its potential applications in enhanced heavy oil recovery

Abstract

The use of functional microbial strains is an emerging strategy for exploiting heavy oil reserves. The aim of this study was to obtain bacterial strains potentially applicable in enhanced heavy oil recovery. A biosurfactant-producing and oil-degrading strain, designated HoB-1, was isolated from a heavy oil sample collected at the Yanchang oilfield (Northwest China). Strain HoB-1 was identified as Bacillus siamensis on the basis of 16S rRNA gene sequence analysis. It showed the potential to produce biosurfactant, which lowered the surface tension of a 7-d-old fermentation broth by 38.6% compared with that of the control. In the presence of the biosurfactant, stable emulsions were formed with different hydrocarbons such as n-hexane, petroleum ether, and light oil. The biosurfactant exhibited high stability, even under extreme temperature (20–100 °C), pH (3.0–13.0), and salinity (0%–30% NaCl) conditions. Bacterial treatment with strain HoB-1 led to the transformation and redistribution of all four heavy oil fractions by reducing the saturates and asphaltenes contents and increasing the aromatics and resins contents. The individual contents of n-alkanes were also increased in the heavy oil upon bacterial treatment. Therefore, B. siamensis HoB-1 is a potential candidate for enhanced heavy oil recovery through biosurfactant production and oil biodegradation.