A simple and efficient biodegradation route for nitroaromatic compounds using a nitroreductase from Bacillus subtilis...

Nitroaromatic compounds are persistent environmental pollutants that pose significant ecological and toxicological risks. Enzymatic reduction of nitroaromatics to the corresponding aromatic amines offers an efficient and selective degradation pathway, whereas simultaneously yielding valuable intermediates for pharmaceutical and agrochemical synthesis. Here, a nitroreductase (NRBs) from Bacillus subtilis was identified that catalyzed nitroaromatic reduction with exceptional efficiency, achieving a yield greater than 99.0% within 2 h without requiring any metal co-catalyst such as V₂O₅. To enhance enzyme stability and eliminate repeated cofactor addition, a "cell-like" co-encapsulation system comprising NRBs, glucose dehydrogenase (GDH), and the cofactor NADH was constructed using ZIF-67 as the encapsulation material. In this design, NRBs was purified and immobilized on polyvinylpyrrolidone (PVP)-modified ZIF-L (P-ZIF-L), whereas NADH and GDH were co-grafted onto poly(acrylamide-co-diallyldimethylammonium chloride) (PADD) to form a PNG complex. The resulting NRBs@P-ZIF-L@PNG@ZIF-67 composite exhibited enhanced catalytic activity, stability, and substrate scope. Furthermore, the "cell-like" co-immobilized system retained 65.0 ± 3.5% of its catalytic yield toward aniline formation after seven reaction cycles, whereas the NRBs-GDH recombinant whole-cell catalyst showed complete deactivation under identical conditions. This work establishes a rapid, simple, green, and sustainable biodegradation strategy for nitroaromatic pollutants, demonstrating the feasibility of using a "cell-like" co-immobilized enzyme system for efficient and reusable biocatalysis.