Fungi found to degrade plastic without pre-treatment and using the plastic as the sole carbon source

My colleague Kate Appleby wrote recently (see here) about the discovery of a particular bacterium able to degrade polyethylene, which is an exciting development because polyethylene and other polymers based on carbon-carbon bonds are generally more difficult to break down then polymers with backbones comprising heteroatoms.

In a recently published report (see here), researchers from Leibniz Institute of Freshwater Ecology and Inland Fisheries and the University of Potsdam led by Professor Hans-Peter Grossart have identified 18 fungal strains isolated from lakes in north-eastern Germany, which can efficiently degrade polymers, including polyurethanes, but also polyethylene and tyre rubber (which like polyethylene is also based on a carbon-carbon backbone). 

The researchers demonstrated that the fungi colonise and degrade plastic polymers in the absence of sugars as an energy source, which some studies have previously suggested to be necessary.  In other words, plastic constituted the sole carbon source.  Likewise, the researchers also found oxidative pre-treatments such as use of ozone, UV light and chemical oxidation or thermal treatments - understood to create reactive functional groups - to be unnecessary.

The researchers reason that fungal species are suited for life in the “plastisphere” because of their adsorptive nutrition mode, apical and invasive growth forms, and their ability to form biofilms and associate with already established biofilms.  Investigations suggested that, at least with the best-degraded plastic tested – polyurethane – initial fungal enzymatic activity affords intermediates that function as a carbon and energy source for the fungi by increasing the concentration of soluble organic carbon available for fungal growth.

Whilst the polyethylene samples, particularly the low density polyethylene plastic bags tested, were much more resistant to degradation then polyurethane, degradation was nevertheless found and, as the researchers note, as fungal diversity is immense and mostly untapped, there are likely other fungal species that may be able to also degrade LDPE.

This research contributes towards the growing body of research seeking to make recycling of plastic, by biodegradation, a reality.

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