Characterization of novel biosurfactant producing strains of Bacillus spp. isolated from petroleum contaminated soil

Biosurfactants are surface active agents with broad range commercial applications in various industries and have considerable advantages over their chemical counterparts. In this study, bacteria were isolated from contaminated and uncontaminated soil and selected during preliminary screening using hemolytic activity, oil spreading and oil collapsed techniques. Isolates with at least more than one positive response to these three methods were subjected to complementary screening by measuring surface tension reduction as well as emulsification capacity. The criteria for selection of potent isolates were surface tension reduction below 40 mN/m and emulsification capacity of more than fifty percent. Using these stepwise screening procedures, two biosurfactant/bioemulsifier producing isolates have been successfully selected that were able to reduce surface tension effectively and one of which formed a stable emulsion. Phylogenic relationships of the two potential candidates were determined comparing the 16Sr DNA gene sequences, revealing them as two isolates of Bacillus subtilis and Bacillus cereus that can be used in pilot scale for industrial production of new biosurfactant/bioemulsifier.