Surfactin, a lipopeptide biosurfactant, produced by Bacillus subtilis is known to reduce the surface tension of water from 72 to 27 mN/m. Potato substrates were evaluated as a carbon source for surfactant production by B. subtilis ATCC 21332. An established potato medium, simulated liquid and solid potato waste media, and a commercially prepared potato starch in a mineral salts medium were evaluated in shake flask experiments to verify growth, surface tension reduction, and carbohydrate reduction capabilities. Total carbohydrate assays and glucose monitoring indicated that B. subtilis was able to degrade potato substrates to produce surfactant. Surface tensions dropped from 71.3 +/- 0.1 to 28.3 +/- 0.3 mN/m (simulated solid potato medium) and to 27.5 +/- 0.3 mN/m (mineral salts medium). A critical micelle concentration (CMC) of 0.10 g/l was obtained from a methylene chloride extract of the simulated solid potato medium.