Purification and characterization of biosurfactants from Nocardia sp L-417

The Nocardia sp. L-417 strain grown with n-hexadecane as a carbon source pr oduced two types of biosurfactant that have different characteristics. Thes e biosurfactants were purified by procedures that included ammonium sulphat e fractionation, chilled acetone and hexane treatments, silica-gel column c hromatography and Sephadex LH-20 gel filtration. The purified biosurfactant s were very stable over a broad range of pHs (2-12) and temperatures (100 d egrees C, 3 h), The biosurfactant type I had strong properties as an emulsi fying agent and as an emulsion-stabilizing agent, whereas type II had a str ong ability to reduce surface tension.