Convenient Immobilization of α-L-Rhamnosidase on Cerium-based Metal-Organic Frameworks Nanoparticles for Enhanced Enzymatic Activity and Recyclability

Graphical Immobilized Rha on MOFs : Herein, we explored five typical metal-organic frameworks (MOFs) as porous carriers to immobilize Rha, and the obtained Rha@Ce-BTC showed the highest enzymatic activity. Also, Rha@Ce-BTC manifested enhanced enzyme-substrate affinity, great reusability/storage stability, and catalytic efficiency compared to free Rha. Significantly, the as-prepared Rha@Ce-BTC might be assembled as a membrane reactor for efficient biocatalysis reactions. The α-L-Rhamnosidase (Rha) is a useful glycoside hydrolase for selectively hydrolyzing the terminal L-rhamnose residues in flavonoids, being vital to food and pharmaceutical industries. However, Rha suffers from low recyclability and poor stability in harsh environments. Herein, we explored five typical metal-organic frameworks (MOFs) as porous carriers to immobilize Rha, and the activities of the resultant Rha@MOF composites were compared with the free enzyme. The locations of the enzyme in MOFs were proved by a series of characterization techniques. It was found that Rha@Ce-BTC (with enzyme immobilization efficiency of 23 % and enzyme loading content of 8.8 %) showed the highest enzymatic activity. The immobilized Rha@Ce-BTC showed 80 % residual activity after five consecutive cycles, suggesting a limited leaching effect. Also, Rha@Ce-BTC manifested markedly enhanced enzyme-substrate affinity and catalytic efficiency compared to free Rha, as supported by Michaelis-Menten kinetic studies. Accordingly, the Ce-BTC would be an appealing carrier for enzyme immobilization, and the as-designed enzyme/Ce-BTC composites are promising candidates for industrial use with remarkably high activity, recyclability, and storage stability.