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

Abstract

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.

Enhanced Bioactivity of Enzyme/MOF Biocomposite via Host Framework Engineering

“…In fact, a high stoichiometric ligand/Zn 2+ applied in the synthesis of esterase@MAF-6 and esterase@ZIF-8 ensures a high crystalline MOF shell over esterase with minimum defects, supporting a fair bioactivity comparison between esterase@ZIF-8 and esterase@MAF-6. Hydrolase@ZIF-8 (e.g., BCL@ZIF-8 (BCL = Burkholderia cepacia lipase), CALB@ZIF-8 (CALB = Candida antarctica lipase B), CRL@ZIF-8 ( Candida rugosa lipase), lipase@ZIF-8 , ) can also be synthesized under a low molar HmIM/Zn ratio (HmIM/Zn ≈ 4). However, spectroscopic and microscopic analysis demonstrated that protein@ZIF-8 samples synthesized under a low HmIM/Zn condition were rich in amorphous phase and coordination defect, which result in larger opening pores than the intrinsic pore structure of ZIF-8. , The minimal structural defects in ZIF-8 and MAF-6 were supported by TGA analysis (Figure S10–S11).…”