Immobilization of Thermomyces lanuginosus lipase on ZnO nanoparticles: mimicking the interfacial environment

Thermomyces lanuginosus lipase (TL lipase) was immobilized covalently on ZnO nanoparticles (NPs) functionalized with small amino acid molecules, like glycine. Glutaraldehyde was used as a spacer between the ZnO/glycine Nps and the enzyme. This study is based on the observation that the favorable conformation of an enzyme (in which the catalytic lid is exposed to reactant molecules) can be obtained at the lipid/water interface and such an interfacial environment can be mimicked by properly designing the carrier used as the support for its immobilization. Glycine functionalized ZnO NPs were covalently bonded with glutaraldehyde and consequently TL lipase enzyme immobilization was carried out by a simple wet chemical method. The resulting assemblies were characterized by using techniques like XRD, UV absorption and photoluminescence spectroscopy. The particle size was determined by using Transmission Electron Microscopy (TEM). The immobilized TL lipase enzyme showed high activity for esterification of oleic acid (C-18) with methanol in an organic medium. The catalyst was recovered and reused several times without any significant loss of activity.