CALB Immobilized onto Magnetic Nanoparticles for Efficient Kinetic Resolution of Racemic Secondary Alcohols: Long-Term Stability and Reusability

In this study, an immobilization strategy for magnetic cross-linking enzyme aggregates of lipase B fromCandida antarctica(CALB) was developed and investigated. Magnetic particles were prepared by conventional co-precipitation. The magnetic nanoparticles were modified with 3-aminopropyltriethoxysilane (APTES) to obtain surface amino-functionalized magnetic nanoparticles (APTES–Fe3O4) as immobilization materials. Glutaraldehyde was used as a crosslinker to covalently bind CALB to APTES–Fe3O4. The optimal conditions of immobilization of lipase and resolution of racemic 1-phenylethanol were investigated. Under optimal conditions, esters could be obtained with conversion of 50%, enantiomeric excess of product (eep) > 99%, enantiomeric excess of substrate (ees) > 99%, and enantiomeric ratio (E) > 1000. The magnetic CALB CLEAs were successfully used for enzymatic kinetic resolution of fifteen secondary alcohols. Compared with Novozym 435, the magnetic CALB CLEAs exhibited a better enantioselectivity for most substrates. The conversion was still greater than 49% after the magnetic CALB CLEAs had been reused 10 times in a 48 h reaction cycle; both eesand eepwere close to 99%. Furthermore, there was little decrease in catalytic activity and enantioselectivity after being stored at −20 °C for 90 days.Keywords:CALB;magnetic nanoparticles;cross-linked enzyme aggregates;resolution;secondary alcohols