Microbial removal of Cr (VI) by a new bacterial strain isolated from the site contaminated with coal mine effluents

A Cr (VI) removing bacteria was isolated from the wastewater collected from Baliya nala (drain) Singrauli, Madhya Pradesh, India where coal mining units discharge their effluents after treatment. The bacterial isolate showed maximum sequence similarity with the Microbacterium paraoxydans and it was submitted to the NCBI GenBank under the accession no. MN650647. The bacterial isolate was named as Microbacterium paraoxydans strain VSVM IIT (BHU) accession no. MN650647. The scanning electron microscopic and energy dispersive X-ray analysis indicated that the cells of the bacterial isolate which were grown in Luria-Bertani broth containing hexavalent chromium got enlarged after the bio-accumulation of Cr (VI) whereas Si, O and C ions were observed on cell surface. The optimum growth was observed at 37 degrees C and pH 7. It was observed that Cr (VI) enhanced the production of antioxidant enzymes such as glutathione S-transferase, catalase, superoxide dismutase and peroxidase within the cells. The concentration of these enzymes increased with the increase in Cr (VI) concentration in the growth medium. The bacterial isolate could tolerate up to 200 mg/L of Cr (VI) and showed a maximum removal efficiency of 99.96% when grown in a medium containing 50 mg/L Cr (VI).