IN-VITRO BIOREDUCTION OF HEXAVALENT CHROMIUM BY VIABLE WHOLE CELLS OF Arthrobacter sp. SUK 1201

A chromium resistant and reducing bacterium Arthrobacter sp. SUK 1201 was isolated from chromite mine overburden dumps of Orissa, India. Viable whole cells of this isolate was capable of completely reducing 100 µM Cr(VI) in chemically defined MS medium within 28 h of incubation under batch cultivation. Reduction of chromate increased with increased cell density and was maximum at a density of 1010 cells/ml, but the reduction potential of the suspended cells decreased with increase in Cr(VI) concentration in the medium. Chromate reducing efficiency was promoted when glycerol and glucose was used as electron donors, while the optimum pH and temperature of Cr(VI) reduction was found to be 7.0 and 35°C respectively. The reduction process was inhibited by divalent cations Ni, Co and Cd, but not by Cu and Fe. Similarly, carbonyl cyanide m-chlorophenylhydrazone (CCCP), N,N,-Di cyclohexyl carboiimide (DCC), sodium azide and sodium fluoride were inhibitory to chromate reduction, while in presence of 2,4 dinitrophenol (2,4 DNP) chromate reduction by SUK 1201 cells remained unaffected.