Hard-to-recycle plastic is consumed by fungi as a meal.

Polypropylene, a hard-to-recycle plastic, has been successfully degraded by two strains of fungi in a new experiment led by researchers at the University of Sydney.

Polypropylene has long been a recycling head scratching conundrum. A common plastic used for a variety of products from packaging and toys to furniture and fashion, it accounts for approximately 28% of the world’s plastic waste, but only 1% of it is recycled.

Now, thanks to the efforts of researchers at the University of Sydney, the resistant polymer may have met its match. Posted on April 14 in material degradation npjTwo common strains of fungi were used to biodegrade polypropylene successfully in a laboratory experiment.

Aspergillus terreus and Engyodontium are typically found in soil and plants, and were able to break down polypropylene after pre-treatment with UV light or heat, reducing plastic by 21% over 30 days of incubation, and by 25%-27 % over 90 days.

“Polypropylene is a common plastic used to make a wide variety of everyday products such as food containers, coat hangers, and packaging films, but its recycling rate is only one percent, which means it is over-represented in plastic waste and pollution globally,” lead author of the study. From the University of Sydney School of Chemical and Biomolecular Engineering, Ph.D. Student Amira Farzana Samat.

The researchers hope that their method can one day reduce the huge amount of plastic polluting the environment and lead to a greater understanding of how plastic pollution degrades naturally under certain conditions.

“Plastic pollution is by far one of the biggest waste problems of our time. The vast majority of it is not sufficiently recycled, which means it often ends up in our oceans, rivers and in landfills. It is estimated that 109 million tons of waste is produced,” Samat said. Plastic pollution has accumulated in the world’s rivers and there are now 30 million tons in the world’s oceans – and sources estimate that this will soon exceed the total mass of fish.”

Researchers say polypropylene is not frequently recycled because of its short life as a packaging material and because it is often contaminated with other materials and plastics, necessitating new methods of recycling that have minimal impact on the environment.

Samat Ph.D. The supervisor, Professor Ali Abbas from the School of Chemical and Molecular Engineering and Chief Architect at Circular Australia, said: “Despite the huge scale of plastic production and consumption, there has been little interest in plastic degradation under environmental conditions, and our understanding of how plastics degrade is limited.”

“One of the big questions raised by our results is ‘What are the naturally occurring conditions that can rapidly follow the decomposition of plastic?'” We seek to further explore the role of biological processes introduced by fungi and other microorganisms. ”

Professor D. Carter, an expert in mycology (the study of fungi) in the College of Life and Environmental Sciences and co-author of the study, said, “Fungi are incredibly versatile and are known to be able to break down pretty much all substrates. This superpower is due to their production of powerful enzymes, which are secreted and used to break down substrates into simpler molecules that can then be taken up by fungal cells.”

“Often, these fungi have evolved to break down wood materials, but this ability can be redirected to attack other substrates. This is why we find fungi growing on all kinds of man-made materials such as carpeting, painted furniture, tiles, shower curtains, upholstery and even car headlights.”

“Recent studies suggest that some fungi may degrade some ‘forever chemicals’ such as PFAS, but the process is slow and not yet well understood. There is also evidence that less plastic is accumulating in the ocean than might be expected based on production and disposal levels. There is speculation that some of this ‘lost’ plastic may have been decomposed by marine fungi.”

How did the process work?

Polypropylene in various forms was initially treated with one of three separate methods: ultraviolet light, heat, and Fenton’s reagent – an acidic solution of hydrogen peroxide and ferrous iron often used to oxidize contaminants.

In a Petri dish, the fungi were applied separately as single cultures to the polypropylene treatment. The validity of the biological degradation was then confirmed by microscopy techniques. While the research did not assess how plastic was degraded by fungi or whether it was metabolized, the researchers hope to conduct more research to determine what kind of biochemical processes are taking place.

next steps

Professor Abbas believes that the low rate of plastic recycling globally presents a “huge circular plastic divide”: “We need to support the development of disruptive recycling technologies that improve the circularity of plastics, especially those that are driven by biological processes like our study. It is important that We note that our study has not yet implemented any optimization of the experimental conditions, so there is plenty of room to reduce this degradation time.”

The researchers will now explore enhancing overall efficiency in shattering polypropylene before seeking investment to scale up the technology and develop a pilot, small-scale commercialization prototype.

Since completing the study, the team has isolated other microorganisms from the marine environment and used a similar process to reduce marine plastic waste, with initial results showing even higher degradation.

Samat said, “We’re very excited about this and have started looking at different ways to improve the decomposition process with these microorganisms. Watch this space.”