Isolation of a biosurfactant producing microorganism, kinetic experiments, and separation of the biosurfactant from liquid culture

A biosurfactant producing bacterium, which was able to grow on olive oil as the sole source of carbon and energy, was isolated from soil. The bacterium, which was identified as Pseudomonas aeruginosa, reduced the surface tension of the culture medium from 51 mN/m to 27 mN/m. Kinetic experiments showed that the existence of a water insoluble carbon source stimulated biosurfactant production considerably. Two methods, namely salting out and change in pH, were examined for the separation of the biosurfactant from the liquid medium. Saturation of the liquid with 340 g ammonium sulfate resulted in 7.2 g solid biosurfactant, while reducing the pH of the medium to 2 resulted in 3.2 g solid biosurfactant. The solid biosurfactant reduced the surface tension of distilled water to 36 mN/m.