Chromium-tolerant bacteria isolated from industrial effluents and their use in detoxication of hexavalent chromium

Three bacterial strains were isolated from effluents of leather (CMBL Cr13, CMBL Cr14) and steel (CMBL Cr15) industries for their possible use in chromium(VI) detoxication of industrial waste. CMBL Cr13 was found to tolerate chromium(VI) up to a concentration of 45 g/L in the medium, while CMBL Cr14 and CMBL Cr15 could tolerate up to 40 g/L. These bacteria were also checked for resistance to other metals. They resisted a lead concentration of 1 g/L and cadmium concentration of 550 mg/L in the medium. They showed optimum growth at pH 7.3–7.5 at a temperature of 35–37°C. Cr^VI-reducing ability of the three strains ranged from 70 to 80% after 3 d of incubation. The possible use of these bacteria in environmental cleanup is discussed.