A practical method for screening for β-galactosidase secreting microbial colonies

Abstract

Microbial colonies were replicated on YNB® agar plates overlaid with soft agar containing the glucose-oxidase/peroxidase (BIOTROL®) system. The pink color developed around the colonies was the result of the reaction of the glucose generated by the extracellular hydrolysis of lactose by β-galactosidase, indicating secretion of this enzyme. This method proved to be very convenient for testing hundreds of colonies grown on agar plates for β-galactosidase secretion by microbial cells.