Production and Optimization of Microbial Surfactin by Bacillus subtilis for Ex Situ Enhanced Oil Recovery

In the research, biosurfactant production and the optimization of biosurfactant production conditions have been examined have been examined using one strain of Bacillus subtilis isolated from agricultural soil. For biosurfactant production, the optimum conditions were sucrose as carbon source, temperature at 37 degrees C and 250 rpm. At 250 rpm, the optimum filling volume of culture media in a 500 mL Erlenmeyer flask was determined as 100 mL. The results show that shaking the flask should increase the oxygen transfer rate from gas phase to liquid phase, but if the filling volume of culture media is more than 100 mL, the oxygen limitation will be governed on the culture medium which results in the reduction of biomass and biosurfactant at 250 rpm. The oxygen limitation causes 23% and 18% reductions of biomass and biosurfactant, respectively. The biosurfactant produced also attained emulsion indexes as 80%, 75%, 68%, and 65% for crude oil, hexadecane, kerosene, and diesel, respectively. Oil displacement experiments in micromodel with kerosene show 25% higher recovery rate in residual oil using the proposed biosurfactant.