| Abstract: | Candida rugosa lipase (CRL) has been immobilized on two kinds of ion-exchange resins, Duolite A 568 and Amberlite IRC 50. These preparations were investigated as a tool for the production of cholesterol oleate in organic media. An increase in temperature up to 40°C increased the rate of reaction and improved the final ester yield. Under optimal conditions, the reaction yield was followed as a time function, for both lipase preparations with an initial water content of 20%. Then, it was observed that about 78% of the oleic acid was esterified after 10 h using CRL immobilized on Duolite, whereas 73% synthesis of cholesterol oleate was reached with CRL immobilized on Amberlite, for the same incubation time. Also, a difference in reaction yield was noticed for the preparations containing sorbitol. In fact, sorbitol treatment might improve the activity of immobilized lipase by preserving the watershell around the catalyst and by increasing the accessibility of the active site to the substrates. In this way, the reaction yield was enhanced, and an increase of 10% synthesis of cholesterol oleate was obtained in both cases. © 1997 SCI. |
