The production and properties of a biosurfactant, synthesized by Bacillus subtilis LB5a strain, using cassava wastewater as substrate were investigated. The microorganism was able to grow and to produce surfactant on cassava waste, reducing the surface tension of medium to 26.6 mN/m and giving a crude surfactant concentration of 3.0 g/L after 48 h. The surface-active compound retained its properties during exposure to elevate temperatures (100 degrees C), high salinity (20% NaCl) and a wide range of pH values. The surfactant was capable of forming stable emulsions with various hydrocarbons. Preliminary chemical characterization revealed that the surfactant has a lipopeptide composition with a CMC value of about 33 mg/L. Cassava wastewater proved to be a suitable substrate for biosurfactant biosynthesis, providing not only bacterial growth and product accumulation but also a surfactant that has interesting and useful properties with potential for many industrial applications. (c) 2005 Elsevier Ltd. All rights reserved.