Production and Characterization of Biosurfactant from Indigenous Bacterium Bacillus amyloliquefaciens USTBb: Feasibility in Microbial Enhanced Oil Recovery

Abstract

In the present study, the production and characterization of biosurfactant by an indigenous Bacillus methylotrophicus USTBb (GenBank accession no.KF496216) was investigated. This bacterial strain was isolated from crude oil contaminated aqueous medium was identified to be a persuasive producer of biosurfactant using crude oil as the sole carbon and energy source. Growth parameters were optimized, with the aim of increasing biosurfactant productivity. Maximum biosurfactant production (5.5 g L^-1) by strain USTBb was reached after 12 d of incubation time and was found to be growth-associated. The strain was able to reduce the surface tension of its cell free culture supernatant containing biosurfactant to 28 mN m^-1. Biosurfactant exhibited excellent emulsification activity against crude oil when compared with various tested hydrocarbon and vegetable oil and it possessed a low critical micelle concentration (CMC) value of approximately            35        mg L^-1, indicating high surface activity. USTBb biosurfactant showed stability under extreme environmental conditions such as high temperature, pH and salinity. Elemental compositions and thermal analysis of biosurfactant was determined by X-ray photoelectron spectroscopy (XPS) and thermal gravimetric (TG) respectively. Furthermore, biosurfactant was found to be an antimicrobial agent against gram positive and Gram negative bacterial strains. Studies on the crude oil recovery using biosurfactant produced by Bacillus sp. USTBb suggested its prospective relevance in microbial enhanced oil recovery (MEOR) and bioremediation.

Keywords: biosurfactant; surface tension; crude oil; microbial enhanced oil recovery; stability; characterization