Isolation of Cr(VI) reducing bacteria from industrial e uentsand their potential use in bioremediation ofchromium containing wastewater

The present study was aimed to assess the ability of Bacillus sp. JDM-2-1 and Staphylococcus capitis to reduce hexavalent chromiuminto its trivalent form. Bacillus sp. JDM-2-1 could tolerate Cr(VI) (4800 g/mL) and S. capitis could tolerate Cr(VI) (2800 g/mL).Both organisms were able to resist Cd2+ (50 g/mL), Cu2+ (200 g/mL), Pb2+ (800 g/mL), Hg2+ (50 g/mL) and Ni2+ (4000 g/mL).S. capitis resisted Zn2+ at 700 g/mL while Bacillus sp. JDM-2-1 only showed resistance up to 50 g/mL. Bacillus sp. JDM-2-1 and S.capitis showed optimum growth at pH 6 and 7, respectively, while both bacteria showed optimum growth at 37°C. Bacillus sp. JDM-2-1 and S. capitis could reduce 85% and 81% of hexavalent chromium from the medium after 96 h and were also capable of reducinghexavalent chromium 86% and 89%, respectively, from the industrial e uents after 144 h. Cell free extracts of Bacillus sp. JDM-2-1and S. capitis showed reduction of 83% and 70% at concentration of 10 g Cr(VI)/mL, respectively. The presence of an induced proteinhaving molecular weight around 25 kDa in the presence of chromium points out a possible role of this protein in chromium reduction.The bacterial isolates can be exploited for the bioremediation of hexavalent chromium containing wastes, since they seem to have apotential to reduce the toxic hexavalent form to its nontoxic trivalent form.