Biotransformation of Nitro Aromatic Compounds by Flavin-Free NADHAzoreductase

Santosh A. Misal, Vivek T. Hum

Abstract

Nitro aromatic compounds are the potential toxic organic pollutant released into the environment and are often resistant to degradation under normal environmental conditions. The biotransformation and/or detoxification of these compounds can be possible by microbial azoreductase enzyme. Azoreductase enzyme has an ability to reduce the toxic nitro group to corresponding amino group. In present report, the flavin-free NADH azoreductase was isolated and purified from alkaliphilic bacteria Bacillus badius. The enzyme was purified by a combination of ammonium sulphate precipitation and size exclusion chromatography. The purified azoreductase has efficiently demonstrated both azoreductase and nitroreductase activities. The biochemical properties of the azoreductase including cofactor requirement, substrate specificity and enzyme inhibition have been studied. The biotransformation of some selected nitro aromatic compounds like 3-nitro benzoic acid, 4-nitro toluene, 3-nitro toluene and 1-chloro-2-nitro benzene by purified azoreductase was carried out at 37°C. The reduction products of these nitro aromatic compounds were analyzed by IR and NMR spectroscopy.