ENCAPSULATION OF BIOCATALYST WITH PVA CAPSULES

PVA capsules were prepared by dropping PVA solution into cold methanol contained in a glass cylinder and subsequent incubation in methanol. The diameter of the capsules decreased slightly with incubation time due to dehydration. The membrane thickness of the capsules was measured by the immobilization of living cells and was found to increase almost proportionally to increasing incubation time in the methanol. Encapsulation of toluene-permeabilized cells having beta-galactosidase activity as an enzyme was attempted under various conditions. The activity and stability of the enzyme in the capsules in phosphate buffer at 28-degrees-C were examined. In a preliminary experiment, methanol inactivated the activity of the free enzyme. However, PVA repressed the inactivation. The activity of the capsules decreased with increasing incubation time, probably due to inactivation of the enzyme activity by methanol and the increase of intraparticle diffusion resistance as a result of growth in membrane thickness. Incubation of the capsules at 0-degrees-C and a methanol temperature gradient in the cylinder used for the preparation of the capsules were effective in improving the enzyme activity of the capsules. The long-term stability of the enzyme activity of the capsules was better than that of free cells, and was improved by incubation at room temperature. Although a temperature gradient in the methanol used in capsule preparation enhanced the activity, it reduced the stability of the capsules.