Utilization of two agroindustrial by-products for the production of a surfactant by Candida sphaerica UCP0995

Medium constituents other than carbon sources affect the production of biosurfactants. In this work we describe a low cost medium for the production of a surfactant by the yeast Candida sphaerica. The medium was formulated only with distilled water supplemented with 5.0% ground-nut oil refinery residue plus 2.5% corn steep liquor as substrates. The isolated biosurfactant was formed with a yield of 4.5 gl⁻¹. The biosurfactant showed high surface tension reducing activity (26 mN m⁻¹), a small CMC value (0.08%), thermal and pH stability with respect to surface tension reducing activity and to emulsification activity against motor oil and a high level of salt tolerance. The biosurfactant was characterized as an anionic glycolipid consisting of 75% lipid and 25% carbohydrate. The potential application of the biosurfactant in oil recovery from sand was demonstrated by the percentile of oil removal (65%). The promising results obtained in this work are noteworthy for possible biosurfactant production from agricultural materials.