To characterize the biosurfactant produced by the USTBa strain, the emulsification index (E24) against the crude oil, other hydrocarbons and olive oil were determined. 5.0 mL of crude oil was added to 5.0 mL of aqueous phase containing the biosurfactant. The mixture was agitated vigorously for 5 min on a vortex and kept undisturbed for 24 h at room temperature. The heights of the oil phase, the aqueous phase, and the emulsified layer were recorded. A standard chemical surfactant, sodium dodecyl sulfate (SDS) was used to compare the emulsification of the biosurfactant. The E24% was determined by using the following equation: