Cascade System Bridging Xanthine Oxidation and L-Arginine for Highly Effective and Non-Toxic Surface Microbial Decontamination.

The present study proposes highly efficient microbial decontamination, employing the synergy between nanobiocatalysis, allowing for highly stable and highly loaded enzyme system, and in situ generation of antimicrobial nitric oxide (NO) from amino acid (l-arginine). Xanthine oxidase (XO) catalyzes the oxidation of xanthine to produce hydrogen peroxide, which reacts with l-arginine, releasing potent antimicrobial agents of nitric oxide. Both loading and stability of the XO enzyme are enhanced by a nanobiocatalytic approach of "enzyme adsorption, precipitation, and crosslinking (EAPC)', which allows for the entrapment of carbon nanotubes (CNTs) with the crosslinked enzyme aggregates and maintains its stability under shaking at 250 rpm for 19 days. On the other hand, free XO loses its activity completely within 4 days. Crosslinked XO molecules on CNTs in the form of EAPC were loaded on the surface of a microporous polymeric membrane filter via polydopamine coating, which shows only a slight decrease in water permeability. In tests using effluent from a municipal wastewater treatment plant, this XO-functionalized membrane displays significantly enhanced antifouling performance against a model bacterium of Staphylococcus aureus. This innovative biocatalytic platform, which couples enzymatic hydrogen peroxide production with subsequent nitric oxide (NO) generation, offers a promising method for microbial decontamination in various applications as well as membrane filtration as demonstrated in this study.