title: Reduction of hexavalent chromium by a novel Ochrobactrum sp. - microbial characteristics and reduction kinetics.
abstract: A Gram negative hexavalent chromium (Cr(VI)) reducing bacteria, Ochrobactrum sp. Cr-B4 (genbank accession number: JF824998) was isolated from the aerator water of an activated sludge process of a wastewater treatment facility of a dye and pigment based specialty chemical industry. It showed a resistance for 1000 mg L(-1) Cr(VI). It exhibited resistance against other heavy metal ions like Ni(2+) (900 mg L(-1) ), Cu(2+) (500 mg L(-1) ), Pb(2+) (800 mg L(-1) ), and Cd(2+) (250 mg L(-1) ), Zn(2+) (700 mg L(-1) ), Fe(3+) (800 mg L(-1) ), and against selected antibiotics. Cr-B4 could efficiently reduce 200 mg L(-1) Cr(VI) completely in nutrient and LB media and could convert Cr(VI) to Cr(III) efficiently. Cr(VI) reduction in nutrient media followed allosteric enzyme kinetics with Km values of 59.39 mg L(-1) and Vmax values of 47.03 mg L(-1)  h(-1) . The reduction in LB media followed Michaelis-Menten kinetics with Km values of 99.52 mg L(-1) and Vmax of 77.63 mg L(-1)  h(-1) . Scanning electron micrograms revealed the presence of extracellular polymeric secretions.
authors.affiliation: National Institute of Technology Karnataka Surathkal, Srinivasnagar, Karnataka, India.
authors.forename: M
authors.initials: M
authors.lastname: Narayani
authors.forename: K
authors.initials: K
authors.lastname: Vidya Shetty
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002413:Cations, Divalent; D002857:Chromium / Q000378:metabolism*; D007700:Kinetics; D019216:Metals, Heavy / Q000378:metabolism; D008855:Microscopy, Electron, Scanning / Q000379:methods; D042041:Ochrobactrum / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D010084:Oxidation-Reduction; D012722:Sewage / Q000382:microbiology; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification
chemical_list: D000900:Anti-Bacterial Agents; D002413:Cations, Divalent; D019216:Metals, Heavy; D012722:Sewage; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion
keywords: Bioreduction; Hexavalent chromium; Isolation; Kinetics; Ochrobactrum