Metal-organic framework-based tunable platform for the immobilization of lipase with enhanced activity in non-aqueous systems

Nowadays, metal-organic frameworks (MOFs) have been emerged as an efficient platform for enzyme immobilization due to their high porosity, tunability, and chemical versatility. In this study, a series of hybrid lipase@NKMOF-101-M (M = Mg, Mn, Zn, Co, or Ni) biocatalysts were constructed through a facile in situ encapsulation method, and the encapsulation and immobilization of lipase in MOFs were carefully validated. The catalytic activity of lipase@NKMOF-101-Mn was 2-fold higher than that of lipase@ZIF-8 and 3-fold higher than that of lipase@MCM-41 due to its excellent dispersibility and hydrophobicity in hexane. The reduced Km value demonstrated a superior affinity of lipase@NKMOF-101s toward to the substrate in non-aqueous reaction system. Moreover, the effects of MOF particle size, metal ions, and enzyme distribution on the catalytic performance of the immobilized lipase were systematically investigated. The results demonstrated that as the particle size of lipase@NKMOF-101s decreased, the apparent enzyme activity increased dramatically. Metal ions in MOFs exhibited activation effect toward to enzyme activity and an approximate 12-fold increase in activity was achieved when transesterification was performed using lipase@NKMOF-101-Mn compared with free lipase. Notably, lipase@NKMOF-101-Co and lipase@NKMOF-101-Ni exhibited substrate selectivity owing to the specific distribution of the lipase in the MOF carriers. Lipase@NKMOF-101s can maintain >80 % of its initial activity even after 5 recycles and a long-term storage (30 days). Consequently, NKMOF-101 is a tunable and sustainable platform for the construction of enzyme@MOFs biocatalysts with superior catalytic performance.