Specific and sensitive plate assay for bacterial lipases

A plate assay to detect bacterial lipase (EC 3.1.1.3) in a medium containing trioleoylglycerol and the fluorescent dye rhodamine B is presented. Substrate hydrolysis causes the formation of orange fluorescent halos around bacterial colonies visible upon UV irradiation. The logarithm of lipase activity from cell-free culture supernatants is linearly correlated with the diameter of halos, thereby allowing quantitation of lipase activities ranging from 1 to 30 nkat.