Surface active properties of a biosurfactant fromCorynebacterium lepus

A mixture of corynomycolic acids (R 1 ‐CH(OH)‐CH(R 2 )‐COOH) isolated from Corynebacterium lepus was shown to have excellent surfactant properties. It caused significant lowering of surface tension in aqueous solution and the interfacial tension between water and hexadecane at all values of pH between 2 and 10. A series of carboxylic acids and some hydroxy‐carboxylic acids and alcohols were also studied as a comparison. None of these caused as large a lowering of the surface and interfacial tensions as the corynomycolic acids. The series of carboxylic acids studied showed that surfactant properties depend on the length of the alkyl chain and the pH of the solution in a manner consistent with the hydrophiliclipophilic balance of these compounds. Hydroxyl substituents caused considerable enhancement of the surfactant properties of long chain carboxylic acids if they were located close to the carboxyl function.