On the importance of the supporting material for activity of immobilized Candida antarctica lipase B in ionic liquid/hexane and ionic liquid/supercritical carbon dioxide biphasic media

A commercial solution of free Candida antarctica lipase B (Novozyme 525L) has been immobilized by adsorption onto 12 different silica supports modified with specific side chains (e.g. alkyl, amino, carboxylic, nitrile, etc.). The immobilized derivatives were assayed for the kinetic resolution of rac-1-phenylethanol in both ionic liquid/hexane and ionic liquid/supercritical carbon dioxide biphasic media. The best results were obtained for the supports modified with non-functionalized alkyl chains and when the in water activity increased from 0.33 to 0.90 (e.g. the CALB/butyl-silica activity was enhanced up to five times). Coating immobilized enzyme particles with ionic liquids (butyltrimethylammonium bistriflimide or trioctylmethylammoniun bistriflimide) resulted in a decrease in activity (10 times), although half-life times were enhanced (up to six times) in hexane media at 95 °C. However, immobilized derivatives coated with ionic liquids clearly improved their synthetic activity in supercritical CO2 by up to six times with respect to the hexane medium, which agrees with the “philicity” between alkyl chain lengths of both the silica support and the cation of ionic liquid.