Bioreduction and biosorption of chromium: Unveiling the role of bacteria

Chromium (Cr) is an abundantly used heavy metal in industrial processes and a high amount of its residues are discharged into waterbodies, soil, and atmosphere due to lack of proper management practices. Therefore, environmental deposition of Cr has a health impact on the environment and organisms living there because of its high persistence and deadly nature. Hence, researchers take it as a challenge and devise a lot of physical, chemical, and biological methods for the transformation of toxic Cr into a less toxic form. This book chapter reveals the role of bacteria in the bioremediation of Cr (VI) through various processes like biosorption and bio-reduction. The purpose of this study is only confined to bacteria because it was observed that bacteria provide maximum potential, resistance, and adaptation toward the reduction of heavy metals, particularly Cr. Moreover, this is not bound to the role of pure bacterial culture in Cr degradation, but the role of the bacterial consortium is also discussed in this study. This study also indicated the ecotoxicity of Cr in the various ecosystems including the effects of its varying concentration on human beings, animals, plants, and microbes. In addition, all bacteria necessitate an enzymatic system for the degradation of pollutants. Therefore, the role of chromium reductase and nitro-reductase enzymes in the bio-reduction of Cr is also enlightened herein.