Reduction of nitroarenes by magnetically recoverable nitroreductase immobilized on Fe3O4 nanoparticles

Abstract

Enzymes as catalysts have attracted significant attention due to their excellent specificity and incomparable efficiency, but their practical application is limited because these catalysts are difficult to separate and recover. A magnetically recoverable biocatalyst has been effectively prepared through the immobilization of a nitroreductase (oxygen-insensitive, purified from Enterobacter cloacae) onto the fe 3 o 4 nanoparticles. the magnetic nanoparticles (Mnps) were synthesized by a coprecipitation method in an aqueous system. The surfaces of the MNPs were modified with sodium silicate and chloroacetic acid (CAA). Using 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) through a covalent binding, nitroreductase was loaded onto the modified magnetic carriers through covalent coupling, and thus, a magnetically recoverable biocatalyst was prepared. The free and immobilized nitroreductase activity was also investigated by the reduction of p-nitrobenzonitrile using nicotinamide adenine dinucleotide phosphate (NAPDH) as a cofactor. The activity of the immobilized enzyme was able to maintain 83.23% of that of the free enzyme. The prepared enzyme can easily reduce substituted nitrobenzene to substituted aniline at room temperature and atmospheric pressure, and the yield is up to 60.9%. Most importantly, the loaded nitroreductase carriers can be easily separated and recycled from the reaction system using an externally applied magnetic field. The magnetically recoverable biocatalyst can be recycled and reused 7 times while maintaining high activities and the activity of the magnetic catalyst can be maintained at more than 85.0% of that of the previous cycle. This research solves the recovery problem encountered in industrial applications of biocatalysts and presents a clean and green method of preparing substituted aniline.Biocatalysis is an important green and sustainable technology, because it is an ideal approach that can be used to meet the challenges of energy conservation and environmental sustainability 1,2 . Enzymes, which are natural biocatalysts, are becoming more and more important in industrial applications, because enzymes can be used at pH values, temperatures and pressures that are moderate, and enzymes form few byproducts and have high activities and an unparalleled selectivity 3-5 . However, there are two challenges that need to be addressed in practical applications. One of the challenges is that enzymes can be denatured, i.e., the native three-dimensional structure unfolds, and this occurs as a result of exposure of the enzyme to solvents or changes in the temperature and pH. Another challenge is that enzyme reuse is often hardly feasible. The recovery and reuse of enzymes is also a decisive factor in the production cost 6 .Specifically, enzymes lack long term stability under processing conditions, and it is very difficult to recover the enzyme from the reaction system. Most heterogeneous systems require either a filtration or centrifugation step or tedious processing of the final react...

Streamlining Design, Engineering, and Applications of Enzymes for Sustainable Biocatalysis

“…180 Zhang et al immobilized a nitroreductase through a carbodiimide-derived covalent bond onto chloroacetic acid and silicate-coated magnetic Fe 3 O 4 nanoparticles. 181 The nitroreductase was used to reduce nitro compounds to substituted anilines. Further examples are provided in a review by Gkantzou et al 182 Another interesting protein-only immobilization idea involves expressing enzymes as part of virus capsids, such as alcohol dehydrogenase D fused to a scaffold protein of bacteriophage P22.…”

“…Cabrera et al used magnetite-permeated diatomaceous earth coated with polyaniline to bind enzymes such as invertase, β-galactosidase, or trypsin, providing improved stability and facile recovery in a magnetic field for multiple re-use . Zhang et al immobilized a nitroreductase through a carbodiimide-derived covalent bond onto chloroacetic acid and silicate-coated magnetic Fe 3 O 4 nanoparticles . The nitroreductase was used to reduce nitro compounds to substituted anilines.…”

Transition Metal‐free Selenium‐mediated Aryl Amines via Reduction of Nitroarenes

“…In this scenario, the development of sustainable, efficient and selective approaches for the reduction of nitroarenes under safe and eco‐friendly conditions is a great challenge. In this regard, photocatalysed [21–23] and biocatalysed [24,25] approaches have recently emerged.…”

“…In this regard, photocatalysed [21][22][23] and biocatalysed [24,25] approaches have recently emerged.…”

A nitroreductase-MOF biocatalyst for the degradation of nitroaromatic contaminants and fluorescent labeling of carbohydrates

“…There is an urgent need to find a feasible method for nitroaromatic reduction to tackle the potential negative issues. Biocatalysis is an emerging green and sustainable technology to cope with the stated challenges, which employs enzymes as natural biocatalysts to realize high catalytic efficiency with safety, remarkable selectivity, and environmental protection [9,10].…”