Osmania University microbiologists find bacteria that can reduce hexavalent chromium

Finding opens up possibility of using the bacteria in industrial effluent treatment plants

Published: 20th August 2017 08:10 AM  |   Last Updated: 20th August 2017 08:10 AM   |  A+A-

Express News Service

HYDERABAD: Researchers from Osmania University’s microbiology department have isolated a bacteria strain that can reduce hexavalent chromium Cr(VI), one of the most toxic pollutants in the environment and a well-known carcinogen. Researchers from OU isolated a strain of bacteria named Achromobacter Xylosoxidans SHB 204, which has the capability to reduce Cr(VI) to a safer form called Trivalent chromium Cr(III). The bacteria was isolated from effluent samples collected from paint and steel industries, pharmaceutical industries and heavy metal contaminated soil sites from Jeedimetla, Patancheru and Balanagar industrial areas respectively. The bacteria was observed to be growing even in conditions having Cr(VI) as high as 1,600 parts per million (ppm). This finding opens up possibility of using the bacteria in places where environment is contaminated by Cr (VI) or in industrial effluent treatment plants. 

Cr(VI) is released as part of various industrial processes especially from tanneries. Electronic waste is also a major contributor of Cr(VI). At sites where e-waste is dumped, Cr(VI) and other heavy metal residues have been found in high concentrations in soil and groundwater including in the city. 
When contacted, Dr Hameeda Bee, lead author of the study said that bacteria Achromobacter Xylosoxidans SHB 204 was found to contain biosurfactant (enzyme released by bacteria outside its body) and also produces a metabolite(enzyme inside its body) named Chromium reductase, which has the ability to leach out Hexavalent chromium from surroundings and turn it into Trivalent chromium. 

The bacteria was also found to be successful in reducing Hexavalent chromium in aerobic conditions (where oxygen is freely available), as well as in anaerobic conditions (where oxygen is unavailable). This is of importance because many polluted sites have anaerobic conditions. 
It was observed that the bacteria could reduce 100-500 ppm Cr(VI) completely in aerobic conditions and reduce 48 per cent of 10-100 ppm of Cr(VI) in anaerobic conditions.  
Dr Bee said that earlier another bacteria was also isolated by her, Bacterium Bacillus subtilis SHB 13, which had capability to reduce Cr(VI) to Cr(III) but it was effective in only aerobic conditions and had only biosurfactant. 

More funds required 
Dr Bee said the present study was possible due to funding through Promotion of University Research and Scientific Excellence (PURSE) scheme by Department of Science and Technology (DST). However, more funds are required to upscale the research and develop a method which can be used to culture the bacteria and extract the biosurfactant and enzyme from them which can be used to reduce Cr(VI) to Cr(III).

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