Lipase immobilization on UiO-66/poly(vinylidene fluoride) hybrid membranes and active catalysis in the vegetable oil hydrolysis

Abstract

Enzyme immobilization engineering is considered a valid strategy to improve the insensitivity of free enzymes to extreme conditions and thus extend their utilization in actual reactions. Although metal–organic frameworks (MOFs) are extensively applied as supports in enzyme immobilization, their separation from the liquid system after catalytic processes is problematic. In comparison, MOF-based membranes show more convenience in the subsequent solid–liquid separation. In this work, we constructed hybrid membranes by incorporating UiO-66 particles into porous polyvinylidene fluoride (PVDF) and then used them to immobilize lipase for the first time. Because of the strong affinity of UiO-66 towards lipase and the large cavity of PVDF, the hybrid membranes exhibited excellent immobilization ability towards lipase, and the resulting immobilized lipase showed an elevated operating temperature in the range of 40–70 °C with preserved activity and evidently improved thermal stability even after being stored at high temperatures for a definite time. The application of PVDF membrane makes the subsequent separation of the immobilized enzyme from the solutions easier. The immobilization kinetics, isotherm, and thermodynamics were analyzed in detail, and the immobilization mechanism was proposed. Furthermore, the immobilized lipase showed reusability and retained 48.2% of its initial activity after 7 cyclic reactions.