Immobilized Hydroxynitrile Lyase: A Comparative Study of Recyclability

Hydroxynitrile lyase from cassava, Manihot esculenta, (MeHNL) catalyzes the formation of (S)-cyanohydrins from HCN and aldehydes or ketones. Four differently immobilized MeHNLs were prepared: by noncovalent immobilization (celite R-633), covalent immobilization (cross-linked enzyme aggregates, CLEA), encapsulation [in a poly(vinyl alcohol) hydrogel Lentikats] and a combination of the above, an unusual immobilization, CLEA encapsulated in a poly(vinyl alcohol) hydrogel. A comparative study of the recyclability of each immobilized MeHNL was performed. Particular attention was paid to the stability and activity of the new immobilized MeHNL-CLEA-Lentikats and to the minimum enzyme loading required to achieve high yields and enantiomeric excesses. MeHNL-CLEA stability was slightly improved by encapsulation into Lentikats and good recyclability rates at low enzyme loading were obtained. However, MeHNL immobilized on celite R-633 exhibited the best recyclability, giving >95% conversion and an enantiomeric excess of 99% during 12cycles.