Biomimetic Mineralization of Metal Ion-Doped Lipase into ZIF-8 Framework for Enhanced Hydrolytic Activity in Biphasic System

Present work encapsulated metal ion dopped-Candida rugosa lipase (CRL) into ZIF structure through biomimetic mineralization and evaluated hydrolytic activity of the immobilized lipase using a biphasic system. Magnesium ion (Mg²⁺) doped-CRL with high hydrolytic activity (237 % of free CRL) was successfully synthesized. Circular dichroism and fluorescence spectroscopy analysis revealed Mg²⁺ doping has changed the conformation of CRL resulted in enhanced structural stability of CRL. The synthesized CRL/Mg²⁺@ZIF-8 had a mesoporous (3.88 nm) structure with good crystallinity. Mg²⁺ doping increased the catalytic activity, substrates affinity (lower Km of 0.4102 mM) and catalytic stability of immobilized CRL. Catalytic activity of CRL/Mg²⁺@ZIF-8 (0.25±0.012 U) was two-fold higher than that of CRL@ZIF-8 (0.10±0.008 U). The synthesized CRL/Mg²⁺@ZIF-8 was used in biosensing of a protox-inhibiting herbicides (nitrofen) in fruit samples. CRL/Mg²⁺@ZIF-8 can be used for biosensing of nitrofen with wide detection range (0-50 μM), low detection limit (0.47 μM) and good recovery rate.