Optimization of Biosurfactant Production and Crude Oil Emulsification by Bacillus Sp. Isolated from Hydrocarbon Contaminated Soil Sample

Biosurfactants, the surface-active compounds produced by microorganisms, have bright prospects in the bioremediation of oil spills. They can also serve as substitutes to synthetic surfactants in food and cosmetic industries. In this study, bacterial strains from soil samples exposed to petroleum hydrocarbons were screened using drop collapse, oil displacement and hemolytic activity tests. Six isolates showed encouraging results in these tests. Based on further assessment of emulsification activity and surface tension reduction, three of the isolates AS03, AS09 and AS01 were judged to be good biosurfactant producers. 16S rRNA gene sequencing confirmed the identity of the best isolate AS03, to be Bacillus licheniformis. Optimization of biosurfactant production and crude oil emulsification by this isolate was attempted using response surface methodology. The optimum levels of three significant variables viz., glucose, yeast extract and toluene were ascertained to be 10.5 g/L, 10 g/L and 5% (v/v), respectively, which resulted in 54.79% emulsification activity (E_24%). The biosurfactant was characterized to be of lipopeptide nature based on the FTIR spectrum. These bacterial strains and the produced biosurfactant hold potential for oil spill clean-up and related environmental applications.