Immobilization of alpha-L-rhamnosidase on a magnetic metal-organic framework to effectively improve its reusability in the hydrolysis of rutin.

α-L-Rhamnosidase (Rha) is a biotechnologically important enzyme that degrades biomass containing natural rhamnoside. Herein, the recombinant Rha was successfully immobilized on magnetic metal-organic frameworks (MOFs), and used to hydrolyze rutin. Magnetic MOFs were constructed by binding Cu2+ and PABA to the surface of Fe3O4 nanoparticles coated with a polydopamine film through coordinate covalent bonds, and the enzyme was attached to the MOFs using the cross-linking agents EDC/NHS. The immobilized enzyme Rha@MOF reached an activity of 25.09 U/g with a lower apparent Km value compared with the free enzyme. The conversion rate of 20 g/L rutin was 91.42%, corresponding to an isoquercitrin productivity of 12.78 g/L/h. Rha@MOF also exhibited significantly improved reusability; the conversion rate was still 73.55% after 30 cycles at 60 °C. These results indicated that the magnetic MOF-immobilized enzyme was a feasible biocatalyst for the conversion of flavonoids with low aqueous solubility.