title: Bacterial chromate reductase, a potential enzyme for bioremediation of hexavalent chromium: a review.
abstract: Hexavalent chromium is mobile, highly toxic and considered as a priority environmental pollutant. Chromate reductases, found in chromium resistant bacteria are known to catalyse the reduction of Cr(VI) to Cr(III) and have recently received particular attention for their potential use in bioremediation process. Different chromate reductases such as ChrR, YieF, NemA and LpDH, have been identified from bacterial sources which are located either in soluble fractions (cytoplasm) or bound to the membrane of the bacterial cell. The reducing conditions under which these enzymes are functional can either be aerobic or anaerobic or sometimes both. Enzymatic reduction of Cr(VI) to Cr(III) involves transfer of electrons from electron donors like NAD(P)H to Cr(VI) and simultaneous generation of reactive oxygen species (ROS). Based on the steps involved in electron transfer to Cr(VI) and the subsequent amount of ROS generated, two reaction mechanisms, namely, Class I "tight" and Class II "semi tight" have been proposed. The present review discusses on the types of chromate reductases found in different bacteria, their mode of action and potential applications in bioremediation of hexavalent chromium both under free and immobilize conditions. Besides, techniques used in characterization of the Cr (VI) reduced products were also discussed.
authors.affiliation: Department of Biotechnology, College of Engineering and Technology, Biju Patnaik University of Technology, Techno-Campus, Ghatikia, Bhubaneswar 751003, Odisha, India. Electronic address: hn_thatoi@rediffmail.com.
authors.forename: Hrudayanath
authors.initials: H
authors.lastname: Thatoi
authors.affiliation: Department of Biotechnology, College of Engineering and Technology, Biju Patnaik University of Technology, Techno-Campus, Ghatikia, Bhubaneswar 751003, Odisha, India.
authors.forename: Sasmita
authors.initials: S
authors.lastname: Das
authors.affiliation: Department of Biotechnology, College of Engineering and Technology, Biju Patnaik University of Technology, Techno-Campus, Ghatikia, Bhubaneswar 751003, Odisha, India.
authors.forename: Jigni
authors.initials: J
authors.lastname: Mishra
authors.affiliation: Department of Biotechnology, College of Engineering and Technology, Biju Patnaik University of Technology, Techno-Campus, Ghatikia, Bhubaneswar 751003, Odisha, India.
authors.forename: Bhagwat Prasad
authors.initials: BP
authors.lastname: Rath
authors.affiliation: Department of Chemistry, North Orissa University, Takatpur, Baripada 757003, Odisha, India.
authors.forename: Nigamananda
authors.initials: N
authors.lastname: Das
mesh_terms: D001673:Biodegradation, Environmental; D002857:Chromium / Q000737:chemistry*; D006801:Humans; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry*
chemical_list: D002857:Chromium; C074702:chromium hexavalent ion; D010088:Oxidoreductases; C063243:chromate reductase
keywords: Bioremediation; Chromate reductase; Chromium resistance; Hexavalent chromium