초록
We synthesized and characterized three novel materials on the basis of zirconia. Despite their three-to six fold higher specific surface area, nanoZrO<SUB>2</SUB>-CeO<SUB>2</SUB> (150m<SUP>2</SUP>/g) and nanoZrO<SUB>2</SUB>-B (296m<SUP>2</SUP>/g) they proved to be less effective supports for a lipase from Candida rugosa than nanoZrO<SUB>2</SUB>-A. For the last, we achieved protein loading of 23mg/g, distributed in a monolayer, which means that 61% of the carrier surface was occupied by the protein. The immobilized on nanoZrO<SUB>2</SUB>-A lipase (nanoZrO<SUB>2</SUB>-A-CRL) exhibited enhanced thermal and solvent stability in comparison to the native enzyme. NanoZrO<SUB>2</SUB>-A-CRL has a half-life at 55<SUP>o</SUP>C of 73min, while for the native enzyme it was only 5.3min. The immobilized enzyme preserved 20% of its activity in six consecutive cycles of the reaction hydrolysis of tributyrin. The immobilization influenced the enantioselectivity of CRL. Using nanoZrO<SUB>2</SUB>-A-CRL under optimal reaction condition in the reaction of esterification of lauric acid with (+/-)-menthol, we achieved menthol conversion of 43% (i.e. 82% of (-) methyl laurate), enantiomeric excess of 97% and enantiomeric ratio of 144. The conformational analysis proved that upon immobilization no serious change in the secondary structure of the lipase from Candida rugosa had occurred.