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Study on the subject of fungi that degrade plastics

Scientists at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) and the University of Potsdam have, according to a study published in Science of the Total Environment, identified fungi in freshwater eco-systems that can efficiently degrade plastics. The results show that strains of Fusarium, Penicillium, Botryotinia and Trichoderma have a high potential to degrade polyethylene (PE), polyurethane (PUR) and tyre rubber. In the study, PUR proved to be the most readily degradable of all the tested plastics. The remarkable thing is, according to the research team, that no addition of sugars as an energy source is needed for breaking down the plastics by the fungi – unlike what was assumed from the studies carried out so far.
 

 

Some fungi are, according to the latest state of scientific knowledge, able to break down complex polymers. The research team selected for its study 18 fungus strains from Lake Stechlin and Lake Mirow, and examined their ability to break down PUR, PE and tyre rubber. The fungi were strains of Fusarium, Penicillium, Botryotinia cinerea EN41 and Trichoderma. The PE plastic came in the form of conventional PE pellets and pieces of plastic bags of low-density polyethylene (LDPE). For the trial, the plastics to be tested were prepared through shredding and the sifting out of particles with a size of between 200 and 500 micrometres. The plastic materials were weighed, disinfected in ethanol and, before use in the degradation test, were dried. The test was carried out in petri dishes on a medium of mineral salt agar (MSA) and in liquid media, to which the fungal strains and plastic particles were added. For control, use was made of agar plates and synthetic media without the addition of plastic particles. All plates were, according to the study, incubated for ten days and the liquid media for up to 16 weeks. As an indicator for the mineralisation of plastic polymers, in other words the breakdown of the plastics by the fungi into organic compounds, the researchers measured the oxygen consumption and carbon dioxide production with an oxygen micro-sensor and a gas chromatograph. In addition, image-forming processes such as Fourier-transform infrared spectroscopy (FTIR) were used for a qualitative characterisation of the most important chemical groups in the fungal biomass, and the light and scanning electron microscope (SEM) for monitoring the morphological changes in the fungus cells. The fungus strains consumed both oxygen and carbon dioxide. In terms of material preference, PUR topped the list, followed by tyre rubber, PE and LDPE. According to the study, the results show that the tested fungi accumulated on the various plastic polymers, colonised them, broke them down and, as the sole source of carbon, utilised them for building up their cells. The study illustrated the potential of these plastic-eating fungi in the battle against plastic pollution, said the researchers. They want to play their part in developing recycling concepts for plastic waste. "The knowledge of more efficient fungus strains, especially for the biodegradation of polyurethane, contributes to the development of large-scale recycling concepts for plastic waste," says study director, Professor Hans-Peter Grossart.
 
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