EFFECTS OF WATER ACTIVITY ON V(MAX) AND K(M) OF LIPASE-CATALYZED TRANSESTERIFICATION IN ORGANIC MEDIA

The V(max) and K(M) of various forms of lipase from Pseudomonas cepacia (powder, adsorbed onto Celite or covalently linked to polyethylene glycol) were determined in organic solvents preequilibrated to water activities (a(w)) from <0.1 to 0.84. The model reaction was the transesterification between n-octanol and vinyl butyrate. It was found that K(M) for the nucleophile increased with increasing a(w) for all three lipase forms. V(max) increased with increasing a(w) for polyethylene glycol-lipase, whereas there was an optimum at intermediate a(w) values (0.11 - 0.38) for lipase powder and Celite-immobilized lipase.