Removal of chromium by a Bacterial consortium isolated from Kolar gold fields and chromium contaminated sites

Abstract

Pollutants from mining and tannery industries adversely affect the natural ecosystem and pose harmful effect to the human beings once it enters the food chain. They also deteriorate the soil fertility and the quality of the ground water. Bioremediation is being viewed as a clean technology for the removal of chromium from tannery effluent. This study was conducted to isolate an efficient bacterial consortium from Kolar Gold Fields and from tannery effluent contaminated site which could remove Chromium. The isolated bacterial consortium could remove chromium at the concentrations of 10 mg/L to 50 mg/L concentration. The optimum concentration found to be 50 mg/L removal up to 96.77 % by the end of 5th day. The isolated bacterial consortium consisted of three strains, which were identified through biochemical tests and 16s rRNA sequencing as Catellicoccus sp., Bacillus safensis strain FFA35, and Pseudomonas stutzeri strain AO 0002. In the present study the isolated bacterial consortium could remove chromium at pH 7 at 37°C up to 96.77 %. The removal of chromium by bacterial consortium was found to be maximum at 25°C up to 97.92 %. The bacterial consortium was supplemented with carbon sources like glucose, lactose, mannitol and fructose. The bacterial consortium could grow their best and remove chromium in the media supplemented with 1 % of fructose showing removal up to 97.85 %. Among nitrogen sources used in the present study, yeast extract could enhance the growth of the organism and the removal reached maximum up to 96.77 %, followed by ammonium nitrate and potassium nitrate showing removal up to 96.08 and 95.12 %. Sodium nitrate could enhance only 93.28 % of removal. Thus, our isolated consortium appears to have great potential for simultaneous bioremediation hexavalent chromium from the contaminated sites.