Biosurfactant Production by Marine-Originated Bacteria Bacillus Subtilis and Its Application for Crude Oil Removal

Abstract

Biosurfactants have been considered as promising candidates for oil spill cleanup as they are generally more biodegradable, less toxic, and better in enhancing biodegradation than chemical surfactants. This study targeted the marine microbial biosurfactants to examine their enhanced production methods and application for the removal of crude oil from soil. The biosurfactants generated by Bacillus subtilis, which was isolated from the Atlantic Ocean, were investigated in this study. The economic production medium using different carbon (n-hexadecane, diesel oil, glycerol, glucose, starch, and sucrose) and nitrogen sources (NaNO₃, (NH₄)₂SO₄, and yeast extract) was studied. The best performance of biosurfactant production was achieved when using glycerol as carbon source and sodium nitrate and yeast extract as nitrogen sources in the substrate. The production rate was enhanced five times compared with that of the original screening recipe. The fermentative production of the generated biosurfactants could reduce the surface tension of water to 27 mN/m and with strong surface activity (∼36.4 mN/m) even after dilution for 10 times. The critical micellar concentration (CMC) of the product was 507 mg/L. A thin layer chromatography (TLC) analysis indicated that the purified product was a mixture of lipopeptide and glycolipid. The microbially produced biosurfactants were further examined as a soil-washing agent to enhance crude oil removal in a soil column system. The removal rates of 58 and 65 % were achieved using the biosurfactant solution with concentrations of 4 and 8 g/L, respectively. The results demonstrated the potential of marine microbial biosurfactants in cleaning crude oil-contaminated soil.

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