Reduction of hexavalent chromium by a novel Ochrobactrum sp. – microbial characteristics and reduction kinetics

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 K m values of 59.39 mg L −1 and V max values of 47.03 mg L −1  h −1 . The reduction in LB media followed Michaelis–Menten kinetics with K m values of 99.52 mg L −1 and V max of 77.63 mg L −1  h −1 . Scanning electron micrograms revealed the presence of extracellular polymeric secretions.