This work investigated the effect of culture medium composition on a biosurfactant production and their total fatty acids content, as well as the surface tension of media, and biomass production by Candida ingens. A factorial experimental design was used to evaluate the combined effect of C/P, C/N-inorganic, C/Fe, C/Mg ratios and yeast extract concentration. The highest biosurfactant production was reached when high C/Fe and high C/P ratio variables were combined; biosurfactant concentration increased by a 3.42 fold. The variable with the highest effect on net decrease surface tension (Delta ST) and fatty acids percentage of C. ingens biosurfactant was yeast extract. The average of Delta ST (25 mN/m) and fatty acids percentage (34.7%) values were enhanced at high yeast extract concentration of 1 g/l. The main conclusion of this study was that the culture composition affected the biosurfactant production by C. ingens. It was also observed that the surface tension and total fatty acids of the biosurfactant were modified as the media composition changed. (c) 2005 Elsevier Ltd. All rights reserved.