Immobilization of lipase on Fe3O4/ZnO core/shell magnetic nanoparticles and catalysis of Michael-type addition to chalcone derivatives

Fe3O4/ZnO core/shell magnetic nanoparticles in 1:1 and 1:2 molar ratios were prepared and characterized by using X-ray powder diffraction, scanning electron microscopy, thermogravimetric analysis, FT-IR spectra, and flame atomic absorption spectrophotometry. Thermomyces lanuginosa lipase (TLL) was then covalently immobilized on the surface of both supports. An immobilization efficiency and yield of 94 ± 2.5% and 86 ± 3.5%, respectively, were measured for nanoparticles in 1:1 molar ratio of Fe3O4/ZnO and immobilization efficiency and yield were 89 ± 2.2% and 81 ± 3.1%, respectively, when lipase was bound to the functionalized nanoparticles in 1:2 molar ratio. The obtained result indicated that the immobilization considerably improved thermal, pH, and operational stability of TLL compared to the soluble enzyme. Moreover, the immobilized enzyme and seven other commercially lipases were examined for Micheal addition of active methylene compounds to chalcones. TLL resulted in the highest yield of the related reaction product compared to other enzymes. For further optimization of Micheal reaction conditions, the effect of some organic solvents was also examined and the obtained results revealed that hydrophobic solvents were more suitable than others.