Studies on the Production of Biosurfactant for the Microbial Enhanced Oil Recovery by Using Bacteria Isolated from Oil Contaminated Wet Soil

Abstract

There are obvious advantages of biosurfactants over chemical surfactants. The developing shortage of oil and rapid increase of oil prices is putting pressure on oil companies to recover as much oil as possible from the wells to sustain the oil economy. Therefore, there is a need to research some “super bugs,” which can produce active and stable biosurfactants in good yields. Five bacterial strains presently isolated from the oil-contaminated soil were selected for the screening for biosurfactant production, via three different methods: surface tension measurements, drop-collapsing test, and emulsification index (EI₂₄) test. Two thermophillic isolates coded as SGI and LFA were found to be the suitable candidates for biosurfactant production. In fact, the biosurfactant produced by the isolate SGI led to the reduction of surface tension up to 26 m/N/m; thus, SGI was selected for the further studies. Biosurfactant production by the thermophillic isolate SGI was found to be growth-associated in all conditions tested. Biosurfactant production using different cheaper carbon substrates was studied. The production of biosurfactant was also studied using isolate SGI, under different conditions of high temperature, NaCl concentration, pH, carbon source, and initial nitrogen concentration. The biosurfactant was found to produce a relatively stable emulsion with hydrocarbons at a wide range of pH. It was also found to be stable at various pH ranges (7.0–14.0) for SGI and was also found to be thermostable for 1 hr at 125°C, based on the value of surface tension. There is a wide array of further studies in the area of microbial enhanced oil recovery (MEOR) including further boosting the activity of the isolate by using adaptation, enrichment, and nutrient enrichment techniques.