Soil detox from Kolkata wetlands

By Maureen Nandini Mitra
Published: Saturday 30 September 2006

a team of Kolkata-based researchers mapping the microbial population of the East Calcutta Wetlands (ecw), has isolated 22 easy-to-culture strains that can help clean up toxic soil and water. The bacteria can help remove metals such as chromium and lead, while some of the strains can degrade oils like petrol, diesel and burnt engine oil, and so help clean up oil spills.

The ecw comprises several waterbodies spread over 5,000 hectares. The wetlands help Kolkata, which doesn't have any sewage treatment plants, treat its sewage. The wetlands' ecosystem uses the refuse in fisheries (which meet one-third of the city's fish requirement) and agriculture and in the process purifies it to a standard equal to many urban secondary level treatment plants.

The research team, from West Bengal University of Technology's microbiology department, analysed the microbial population in the wetlands' soil and water and found strains from 12 bacterial phyla. "Once I had this (bacterial phyla) map, I began to find out which microbes would be useful to us," says Shaon Ray Chaudhuri, co-writer of the study. The team found 20 strains of bacteria that could grow in the presence of heavy concentrations of metals like lead, iron, cobalt, chromium, nickel and silver. "These bacteria can remove metal toxicity and could help treat waste from battery factories and tanneries." Their findings were published in the July 25 issue of Current Science (Vol 91, No 2).

Nine of the 22 strains can degrade oils, while another nine secrete extra-cellular protease, an enzyme that can be used in pharma and soap industries. Of these, one is a secondary protease that, when added to detergents, helps remove tough grease and oil stains. Yet another strain was found to cause "de-hairing" of hides and might be useful in the leather tanning industry.

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