Azizi_2026_Nanoscale.Adv__

This study focused on immobilizing Humicola insolens lipase onto magnetic nanoparticles of ZrFe(2)O(4) and ZrFe(2)O(4)@UiO-66-NH(2) using precipitation-crosslinking and covalent binding methods. Characterization techniques, including FT-IR, SEM, energy-dispersive X-ray spectroscopy, X-ray diffraction, BET, DLS, and thermogravimetric analysis, confirmed the successful synthesis and functionalization of the supports. Enzyme immobilization was assessed using different buffer systems, and Tris-HCl buffer at a low concentration was chosen as the optimal medium due to its compatibility with the support structure. The precipitation-crosslinking method resulted in enzyme loadings of 260 mg g(-1) for ZrFe(2)O(4) and 226 mg g(-1) for ZrFe(2)O(4)@UiO-66-NH(2), achieving immobilization efficiencies of about 40% and 60%, respectively. In contrast, the covalent binding technique significantly improved the enzyme loading and immobilization efficiency, with ZrFe(2)O(4) achieving 305 mg g(-1) and 65% efficiency. ZrFe(2)O(4)@UiO-66-NH(2) demonstrated even greater performance, with the immobilization efficiency exceeding 80%. The reusability and thermal stability of the immobilized lipase improved markedly with covalent binding, particularly for the biocatalyst obtained by immobilizing lipase on ZrFe(2)O(4)@UiO-66-NH(2) nanoparticles. This biocatalyst retained over 70% of its activity after five reuse cycles and retained 40% activity at 80 degreesC. In contrast, the precipitation-crosslinking method led to a significant decline in activity during successive cycles, with no observable enhancement in enzyme thermal stability using this technique.