Treatment of diesel- and kerosene-contaminated water by B. subtilis SPB1 biosurfactant-producing strain.

This study investigated the efficiency of hydrocarbon utilization by B. subtilis SPB1, a biosurfactant-producing strain. Microbial growth, biosurfactant production, and hydrocarbon biodegradation were studied in a liquid mineral medium, supplemented with 2% hydrocarbons in both the absence and in the presence of 0.1% yeast extract. Preliminary studies showed that maximum growth was registered with a 2% hydrocarbon solution. Results showed that the addition of yeast extract greatly stimulated microbial growth and thus induced biosurfactant production. Furthermore, biodegradation efficiencies were higher in the presence of yeast extract. Kerosene fuel was more recalcitrant to biodegradation than diesel oil. This study's findings suggest that the addition of an organic nitrogen source stimulates tension-active agents' production, which emulsifies hydrophobic compounds and enhances their biodegradation and microbial growth.