The meat processing industry is seeking new applications for abundantly available, inexpensive animal fats. Sophorolipid production by Candida bombicola was studied as a model for fat utilization for biosurfactant production. Inoculum medium components (glucose, animal fat, ammonium sulfate, corn steep liquor urea and potassium phosphate) were optimized for rapid growth. Similar components were chosen to design a production medium for sophorolipid production. Corn steep liquor provided vitamins and minerals, and fat plus glucose were used as carbon sources. Maximum growth was obtained at 30 degrees C but greater sophorolipid production occurred at 27 degrees C. In a pH-controlled fermenter (maintained at pH 3.4 after the first 24 hours) 120 g l(-1) of sophorolipid was obtained in 68 h. Silica gel column chromatography of the extracted sophorolipid revealed the presence of at least six components, including a major component comprising 45% of the total sophorolipids. Cells at the end of fermentation contained 37% protein and 14% lipids. Amino acid analysis indicated a high quality of protein, although with a lower than desired tryptophan level A reduction in production time with high volumetric productivity and inexpensive raw materials make sophorolipid competitive against surfactants used in the food and cosmetics industries.