Dump wars

Fungi can even chew on plastic when it comes to food  

By Nidhi Jamwal
Published: Wednesday 30 June 2010

imageINDIA generates over 10,000 tonnes of plastic waste daily. This is almost 10 per cent of the entire solid waste generated. Mukesh Doble and his student Trishul Artham from the Indian Institute Technology in Chennai spent a year experimenting with fungii that can degrade bisphenol A (BPA)-containing plastic.

BPA is used as a plasticizer in baby bottles, medical devices and food can linings to make the plastic clear and shatter-proof. The chemical is a known hormone disruptor.

Polycarbonate plastic was suspended in a liquid medium along with three fungal strains Engyodontium album, Pencillium adametzii and a commercial white-rot, Phanerochaete chrysosporium. During the experiment, they were termed SF1, SF3 and SF2 respectively.

While Doble isolated SF1 and SF3 from the soil in a plastic dumpsite in Chennai, SF3 is a well known fungus used for bioremediation. “We went looking for fungal strains at a plastic waste dumpsite because organisms have a natural tendency to adapt to eating locally available food over a period of time. Here their food was polymer. Petroleum-eating organisms can, similarly, be found at a petroleum waste dumpsite,” explained Doble.

The three fungal strains did justice to their food habits in the lab—they digested the BPA-containing plastic, said the study recently published in Biomacromolecules.

Before introducing the three fungal strains into the BPA-containing plastic, the polymer was UV-radiated for 10 days. Pre-treatment is important as it helps the fungi develop a biofilm on the surface of the polymer. It is only after the fungus has multiplied and adhered to the surface that it can start feeding on the polymer. The polycarbonate is their source of carbon or, better put, energy. The process of plastic degradation, though, is very slow. After 12 months polymer weight reduced 5 per cent.

“This means that biodegradation of one kg plastic waste can take up to 100 years. But the positive thing is that the fungi will not let BPA leach into the environment,” said Doble. These fungal strains can be used in landfills for safer decomposition of plastic waste.

India produces 2.7 million tonnes of BPA plastic every year. In January this year, the US food and Drug Administration raised concern about developmental problems in infants and children exposed to BPA. Last year six baby bottle manufacturers decided to remove BPA from their products. Canada has already banned BPA from baby bottles.

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