L-cysteine-coated magnetite nanoparticles as a platform for enzymes immobilization: Amplifying biocatalytic activity of Candida antarctica Lipase A

This study presents the synthesis of magnetite nanoparticles coated with L-cysteine (Fe₃O₄@LC) and their subsequent utilization as a support matrix for the immobilization of Candida antarctica Lipase A (CALA). The immobilization process involved physical interactions and covalent bonding mediated by glutaraldehyde. Comprehensive characterization was conducted using techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM), providing compelling evidence of a successful synthesis. Under optimized conditions, employing 1 mg of protein per gram of support, pH 7 in a 25 mM phosphate buffer, and a 5 h reaction at 25 °C, immobilization on glutaraldehyde-activated support achieved an impressive yield of 85.0 % ± 2.6, accompanied by a specific activity of 212.5 ± 1.3 U/g, outperforming the physical adsorption approach. Remarkably, the immobilized enzyme exhibited higher activity than the free enzyme at alkaline and acidic pH levels. Furthermore, thermal and pH inactivation studies revealed that the biocatalyst's half-life exceeded that of free CALA by more than 8 times at pH 10. These results underscore the potential of the Fe₃O₄@LC-GLU-CALA system as a robust biocatalytic matrix with promising applications in biodiesel production, ester synthesis, and pharmaceutical manufacturing.