Plastic waste is now less of a nuisance and more of a threat. The lack of degradability of polymeric materials has resulted in vast levels of health hazards and environmental pollution. It is now the most common debris found in oceans with eight million tonnes added each year. Various approaches have been developed, though more research is still in progress to find ways to reduce the impact of these plastics.
Recently when researchers were studying soil samples from a landfill in Islamabad, Pakistan, they found a particular fungus that degrades and consumes polyester polyurethane: a type of plastic. Polyester polyurethane is used in the manufacture of various products including synthetic leather, tyres, adhesives, supermarket trolleys etc.
The study, published in the science journal Environmental Pollution, isolated the fungus identified as Aspergillus tubingensis found in the dump, to assess its ability to degrade polyester polyurethane. The team tested the fungus’s ability to degrade polyurethane in three different ways: on an agar plate, in liquid, and after burial in soil. The results showed the level of degradation of the plastic in the agar medium was the highest, followed by liquid and last burial. It was also noted that after two months in a liquid medium, the polyurethane film was completely degraded into smaller pieces.
The fungus uses enzymes to break chemical bonds in the plastic, and then uses its tiny root-like structures called mycelia, to further break apart the material. A piece of plastic can be digested within weeks. This method isn’t perfect since the fungus creates some greenhouse gas emissions during the process, while the amount of the emissions are not known yet.
“We decided to take samples from a rubbish dump in Islamabad, Pakistan, to see if anything was feeding on the plastic in the same way that other organisms feed on dead plant or animal matter”, says Dr. Sehroon Khan, a postdoctoral researcher at the World Agroforestry Centre and lead scientist of this study. “The fungus secretes enzymes that degrade the plastics, and in return, the fungus gets food from it by dissolving the plastics”.
The next goal of the team is to determine the ideal conditions for fungal growth, such as the temperature, pH, preference of substrates in the growing environment etc. This could potentially be a way of dealing with plastic in landfills, waste treatment plants or even soil contaminated with plastic. Currently, the researchers are seeking funds to create a large-scale system for plastic degradation. While this is a promising solution for the environmental pollution of plastics, it doesn’t take care of the source which implies that we need to reduce the amount of plastic waste produced.
1] Khan, S., Nadir, S., Shah, Z. U., Shah, A. A., Karunarathna, S. C., Xu, J., … & Hasan, F. (2017). Biodegradation of polyester polyurethane by Aspergillus tubingensis. Environmental Pollution, 225, 469-480.