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 1000mgL-1 Cr(VI). It exhibited resistance against other heavy metal ions like Ni2+ (900mgL-1), Cu2+ (500mgL-1), Pb2+ (800mgL-1), and Cd2+(250mgL-1), Zn2+ (700mgL-1), Fe3+ (800mgL-1), and against selected antibiotics. Cr-B4 could efficiently reduce 200mgL-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 59.39mgL-1 and Vmax values of 47.03mgL-1h-1. The reduction in LB media followed Michaelis-Menten kinetics with Km values of 99.52mgL-1 and Vmax of 77.63mgL-1h-1. Scanning electron micrograms revealed the presence of extracellular polymeric secretions. 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.