Improvement of catalytic activity of Candida rugosa lipase in the presence of calix[4]arene bearing iminodicarboxylic/phosphonic acid complexes modified iron oxide nanoparticles.

In the present study, iron oxide magnetite nanoparticles, prepared through a co-precipitation method, were coated with phosphonic acid or iminodicarboxylic acid derivatives of calix[4]arene to modulate their surfaces with different acidic groups. Candida rugosa lipase was then directly immobilized onto the modified nanoparticles through sol-gel encapsulation. The catalytic activities and enantioselectivities of the two encapsulated lipases in the hydrolysis reaction of (R/S)-naproxen methyl ester and (R/S)-2-phenoxypropionic acid methyl ester were assessed. The results showed that the activity and enantioselectivity of the lipase were improved when the lipase was encapsulated in the presence of calixarene-based additives; the encapsulated lipase with the phosphonic acid derivative of calix[4]arene had an excellent rate of enantioselectivity against the (R/S)-naproxen methyl and (R/S)-2-phenoxypropionic acid methyl esters, with E=350 and 246, respectively, compared to the free enzyme. The encapsulated lipases (Fe-Calix-N(COOH)) and (Fe-Calix-P) showed good loading ability and little loss of enzyme activity, and the stability of the catalyst was very good; they only lost 6-11% of the enzyme's activity after five batches.