Assessment of heavy metal tolerance and hexavalent chromium reducing potential of <em>Corynebacterium paurometabolum</em> SKPD 1204 isolated from chromite mine seepage

Abstract

Corynebacterium paurometabolum SKPD 1204 (MTCC 8730), a heavy metal tolerant and chromate reducing bacterium isolated from chromite mine seepage of Odisha, India has been evaluated for chromate reduction under batch culture. The isolate was found to tolerate metals like Co(II), Cu(II), Ni(II), Mn(II), Zn(II), Fe(III) and Hg(II) along with Cr(VI) and was resistant to different antibiotics as evaluated by disc-diffusion method. The isolate, SKPD 1204 was found to reduce 62.5% of 2 mM Cr(VI) in Vogel Bonner broth within 8 days of incubation. Chromate reduction capability of SKPD 1204 decreased with increase in Cr(VI) concentration, but increased with increase in cell density and attained its maximum at 1010 cells/mL. Chromate reducing efficiency of SKPD 1204 was promoted in the presence of glycerol and glucose, while the highest reduction was recorded at pH 7.0 and 35 °C. The reduction process was inhibited by divalent cations Zn(II), Cd(II), Cu(II), and Ni(II), but not by Mn(II). Anions like nitrate, phosphate, sulphate and sulphite was found to be inhibitory to the process of Cr(VI) reduction. Similarly, sodium fluoride, carbonyl cyanide m-chlorophenylhydrazone, sodium azide and N, N,-Di cyclohexyl carboiimide were inhibitory to chromate reduction, while 2,4-dinitrophenol appeared to be neither promotive nor inhibitory to the process.

Keywords

• <em>Corynebacterium paurometabolum</em>
• mine seepage
• metal tolerance
• antibiotic resistance index
• Cr(VI) bioremediation