An efficient biosurfactant-producing and crude-oil emulsifying bacterium Bacillus methylotrophicus USTBa isolated from petroleum reservoir

An efficient biosurfactant-producing bacterium was isolated and cultured from petroleum reservoir in northeast China. Isolate was screened for biosurfactant production using haemolytic assay, Cetyl Trimethyl Ammonium Bromide agar plate assay (CTAB) and the qualitative oil-displacement test. Based on partial sequenced 16S rDNA analysis of isolate, USTBa, identified as Bacillus methylotrophicus with 100% identity. This bacterium was able to produce a type of biosurfactant with excessive foam-forming properties. The maximum biosurfactant production was obtained when the cells were grown on minimal salt medium containing 2% (v/v) crude-oil as the sole source of carbon at 35 °C and 180 rpm after 192 h. This strain had a high emulsification activity and biosurfactant production of 78% and 1.8 g/L respectively. The cell free broth containing biosurfactant could reduce the surface tension to 28 mN/m. Fourier transform infrared (FT-IR) spectrum of extracted biosurfactant indicates the presence of carboxyl, hydroxyl and methoxyl functional groups. Elemental analysis of the biosurfactant by Energy dispersive X-ray spectroscopy (EDS) reveals that the biosurfactant was anionic in nature. The strain USTBa represented as a potent biosurfactant-producer and could be useful in variety of biotechnological and industrial processes, particularly oil industry.

► Isolated indigenous strain USTBa was identified as Bacillus methylotrophicus.
► Growth-associated biosurfactant production from strain USTBa.
► Strain USTBa able to produce biosurfactant with excessive foam-forming properties.
► USTBa biosurfactant has stability at extreme pH, salinity and temperature.
► Biosurfactant with excellent surface tension reduction and emulsification activity.