3.2. Bacterial growth, biosurfactant production and residual crude oil removal It has been reported that the endurance of microbes in hydrocarbons supplemented medium is a key factor in determining the biodegradation of hydrocarbons either in soil or liquid phase [7]. Since the strain USTBa was isolated from a petroleum reservoir, they could survive and adapt to the oil-contaminated aqueous medium very easily [3,18]. Particularly, there are only a few microorganisms known to be surface-active compounds producers while growing on crude oil hydrocarbons [4].