To determine the cleaning ability of the biosurfactant, the inner walls of a beaker was coated with motor oil. To remove the adhered oil, 50 mL of the cell-free broth was added to the beaker, vortexed for 1.0 min and allowed to stand for 6 h. Following the washing, the residual oil was treated with 50 mL of hexane twice. The solvent was evaporated at 50 ºC and the amount of oil removed was determined by gravimetry