ESTERIFICATION ACTIVITY OF IMMOBILIZED LIPASE ENTRAPPED IN THERMAL-PHASE TRANSITION GEL

Lipase was entrapped in poly-N-isopropylacrylamide gel beads which underwent thermally induced phase transition. Catalytic activity of the immobilized enzyme in the gel beads (IEG) was studied for esterification in organic medium and, for comparison, hydrolysis in aqueous medium. The activity of IEG changed significantly before and after the phase transition. The esterification activity leapt up with the phase transition at which the gel altered from swollen to shrunken state, whereas the hydrolysis activity fell. The esterification activity change was thought to be caused by change in the amount of environmental water in and around the IEG. To clarify the effect of environmental water on the esterification activity, four IEGs, different in their state and amount of environmental water, were employed for the esterification, and their activities were compared. IEG was most active when it shrunk and was surrounded with a suitable amount of water.