A biosurfactant-producing bacterium, isolate2/3, was isolated from mangrove sediment in the south ofThailand. It was evaluated as a potential biosurfactantproducer. The highest biosurfactant production (4.52 g/l)was obtained when the cells were grown on a minimal saltmedium containing 25 % (v/v) palm oil decanter cake and1 % (w/v) commercial monosodium glutamate as carbonand nitrogen sources, respectively. After microbial cultivation at 30 C in an optimized medium for 96 h, thebiosurfactant produced was found to reduce the surfacetension of pure water to 25.0 mN/m with critical micelleconcentrations of 8.0 mg/l. The stability of the biosurfactant at different salinities, pH and temperature and also itsemulsifying activity was investigated. It is an effectivesurfactant at very low concentrations over a wide range oftemperatures, pH and salt concentrations. The biosurfactantobtained was confirmed as a glycolipid type biosurfactantby using a biochemical test, fourier-transform infraredspectroscopy, MNR and mass spectrometry. The crudebiosurfactant showed a broad spectrum of antimicrobialactivity and also had the ability to emulsify oil and enhancepolyaromatic hydrocarbons solubility.