Comparative study of Cr(VI) uptake and reduction in industrial effluent by Ochrobactrum intermedium and Brevibacterium sp.

Two chromium-resistant bacterial strains, CrT-1 and CrT-13, tolerant up to 40 mg K2CrO4 ml(-1) on nutrient agar, 25 mg ml(-1) in nutrient broth, and up to 10 mg ml(-1) in acetate-minimal media, were identified as Ochrobactrum intermedium and Brevibacterium sp., respectively, on the basis of 16S rRNA gene sequencing. Uptake of chromate was greater in living cells than in heat-killed or dried cells. CrT-1 reduced 82%, 28% and 16% of Cr(VI) at 100, 500, and 1000 mug ml(-1) after 24 h while CrT-13 reduced 41%, 14% and 9%. Other heavy metals at low concentrations did not affect these reductions. At 150 and 300 mug ml(-1) in an industrial effluent sample Cr(VI) was reduced by 87% and 71%, respectively, with CrT- 1 and by 68% and 47% with CrT-13.