Caseinase is an enzyme that hydrolyzes casein, the major protein component in milk. Lipase production is common to bacteria that grow in foods rich in fats such as butter and mayonnaise. This enzyme breaks fats into its components glycerol and fatty acids. Agar which contains lipids prepared from egg yolks is used in identifying lipolytic activity. The agar loses its opacity surrounding growth of a lipase-producing bacterium.
Most enzymes are endoenzymes .
They are produced in the cell and catalyze intracellular reactions. Streak each organism across a small portion of the agar surface. Cover the surface with iodine. Rotate to distribute the iodine into a thin layer. Do not flood the plate.