ENHANCED CATALYTIC EFFICIENCY OF ENZYMES IN ORGANIC MEDIA WITH THE ADDITION OF THE SOLID SUPPORT - EFFECT OF SILICA-GEL ON REACTION-RATES AND ENZYME AGGLOMERATION

Enzymatic esterification of octanoic acid with methanol in cyclohexane was investigated using Candida rugosa lipase in the absence or presen ce of silica gel. The lipase was added in the form of a suspended drie d powder, and the effects of water content and shaking rate on the rea ction rates were examined. It was found that the maximal reaction rate could be markedly enhanced by the addition of silica gel to the mediu m with shifting the optimal water content to a higher value. In order to identify the reasons for the rate improvement in the presence of th e support, the effects of water content and silica gel on the distribu tion of water, partitioning of the substrates, enzyme inactivation, an d agglomeration of enzyme particles were examined. Under the condition s studied, enzyme agglomeration was the largest factor reducing activi ty at high water contents and the enhanced activity with the addition of silica gel was mainly attributed to effective reduction of agglomer ate size in the solvent medium. It was also shown that repeated use of the enzyme is very effective in the presence of silica gel. The yield s in successive batch runs increased with increasing the ratio of sili ca gel to the enzyme.