Microbial biodegradation of nitrophenols and their derivatives: A Review

Today, nitrophenols (NPs) represent chemicals highly in demand not only due to their function in synthetic chemistry but also due to their huge applications in several industries. Such diverse requirements and applications has resulted in a widespread abundance of these chemicals. Improper application and waste disposal practice results in the continuous discharge of these compounds into the environment and causes pollution threat to soil, groundwater, river water, etc. These xenobiotic chemicals are hazardous, toxic, carcinogenic, and mutagenic which results in serious health problems. The Nitro group present in the phenol makes them recalcitrant which causes the persistence of these chemicals in the environment. Although several chemicals, electrochemical, physical, and physicochemical methods have been proposed, bioremediation approaches mainly involving bacteria are considered best. To date, very few successful attempts (related to microbe-assisted bioremediation) have been carried out with environmental habitats for the removal of NPs (both in-situ and ex-situ attempts). So, as far as the effectiveness of the bioremediation process for NP decontamination is concerned, we are far away. More explorative studies using efficient aerobic-anaerobic NP degrading bacterial consortium (or combination of microbes- plant systems) and advanced techniques including omics approaches and nanotechnologies may help towards developing better practicable bioremediation approaches, in the future. This review article focuses on the list of nitrophenol degrading microorganisms, biodegradation pathways of NPs, bioremediation by immobilized cell technique, and the advantages and disadvantages of bioremediation. This article will increase our knowledge of the biodegradation of NPs.