A drop-collapsing test for screening surfactant-producing microorganisms

Abstract

A sensitive rapid method was devised for screening bacterial colonies that produce surfactants. Drops of cell suspensions of surfactant-producing colonies collapsed on an oil-coated surface. Drops of cell suspensions of colonies that did not produce, or produced very low concentrations of surfactants remained stable. The stability of drops was dependent on biosurfactant concentration and it correlated with surface tension but not with emulsifying activity. Microbial colonies grown in the presence of carbohydrates or hydrocarbons could be readily screened for surfactant production by this method.