FUNCTIONAL CAPSULE MEMBRANES .32. LIPASE-IMMOBILIZED CAPSULE MEMBRANES AS A REACTOR IN ESTER SYNTHESES AND HYDROLYZES IN ORGANIC-SOLVENTS

A lipase-immobilized capsule membrane reactor was prepared: poly(p-aminomethyl)styrene (polyAMS) or poly(p-chloromethyl)styrene (polyCMS) was surface-grafted onto a porous nylon capsule membrane (diameter: 2 mm, membrane thickness: 5-mu-m) and a lipase was immobilized to the side-chains of the grafted polymers on the capsule. When the lipase-immobilized capsule containing a buffer solution in the inner aqueous core was immersed in an organic solution of lipophilic substrates, the following reactions were effectively catalyzed compared with reactions catalyzed by a native lipase in water-in-oil emulsions: (i) syntheses of trilaurin from lauric acid and monolaurin, (ii) ester exchange reactions between tricaprylin and lauric acid, and (iii) hydrolyses of trilaurin. The catalytic reactions occur at the interface between the inner aqueous phase and the outer organic phase of the capsule membrane, where the lipase is protected from the organic solvents by the soaked buffer solution from inside. The reactivity of enzymes is affected largely by the lipophilicity of the polymer chains (polyAMS or polyCMS) grafted on the capsule and the polarity of the outer organic solvent.