Pseudomonas sp. EL-G527 was grown to produce a biosurfactant on 2% n-hexadecane as the energy and carbon source. This biosurfactant significantly reduced the surface tension of water from 72 to 28 dyne/cm at a critical micelle concentration(CMC) of 140 mg/l at pH 2.0. As the pH value decreased, the reduction in the surface tension due to the biosurfactant increased. The surface activity of the biosurfactant was unaffected when the NaCl concentration was increased to 5% and the calcium ion concentration increased to 100 mM, plus it remained stable at 10$0^{circ}C$ for 180 min.