Hexavalent Chromium Reduction in Tannery Effluent by Bacterial Species Isolated from Tannery Effluent Contaminated Soil

This study was conducted to isolate and characterize Cr(VI) [chromate] reducing bacteria from soil contaminated with tannery effluent (Kanpur, India) and evaluate these bacteria for Cr(VI) reduction activity. A comparative growth and reduction study was conducted in AMM (acetate minimal media; considering acetate as an economical and easily available carbon source) and in the tannery effluent for further possible application to remove Cr(VI) from the tannery effluent and other contaminated environment. The promising results encourages for the development of cost effective and user friendly bioremediation technology for tannery industry. Three bacteria (B2, B4 and B9) possessing ability to grow and reduce 1.24 mg L-1 of Cr(VI) below the detection limit within 24 h in absolute tannery effluent without any amendment, were evaluated for their reduction property in LB (Luria Bertani) broth media amended with 50, 100 and 200 mg L-1 of Cr(VI) concentrations. All three bacteria were gram positive and belong to the genus Bacillus. In a comparative Cr(VI) reduction study in three different media (LB, AMM and tannery effluent), isolate B9 kept the activity non-significantly different, irrespective of the type of media. However, isolate B4 showed significant influence of the media on its reduction ability. The independent growth study of these isolates distinctly indicates that tannery effluent is preferred over AMM; however, activity and growth were not linked to these isolates. The subsequent time course study further reveals their relevance and potential for application in environmental samples.