CATALYTIC BEHAVIOR OF LIPASES UNDER LAUNDRY CONDITIONS

The rate of lipase-catalyzed hydrolysis of triolein by three different lipases has been studied under a number of conditions which are expec ted to be important when they are used as aids to oily soil removal in laundry detergents or dishwashing liquids. Surface active molecules s uch as surfactants or fatty acids strongly inhibit the rate of lipase- catalyzed hydrolysis. This inhibition appears to involve competition b etween enzyme and surfactant for the interface thereby interfering wit h the interfacial activation process. This results in quite different rates for surfactant-filled versus surfactant-empty interfaces. Unboun d calcium ions accelerate the rate of reaction in both the surface-fil led and surface-empty interfacial state. For product inhibition the ra te acceleration can be related to the precipitation of the ionized fat ty acid as the calcium soap, removing its inhibiting effect. Very low rates of triolein hydrolysis were observed in the laundry detergents s tudied. This is thought to be the result of the combined negative infl uence of both the builder and the surfactant. Such a low amount of hyd rolysis suggests that these lipases do not contribute significantly to soil removal by creating easily solubilized molecules (i.e. the fatty soap and diglycerides) rather, if they are effective in increasing so il removal during the wash, it must be regarded as a result of a benef icial change in the condition at the soil-water interface, such as int erfacial tension lowering, as a consequence of the surface active prod ucts of lipolysis.