These fungi might be the solution to finally get rid of plastic.

In a cutting-edge experiment conducted by experts at the University of Sydney, polypropylene, a plastic that’s notoriously difficult to recycle, has been successfully biodegraded by not one, but two strains of fungi.

This extraordinary achievement brings humanity one step closer to a world where even the most stubborn forms of plastic waste can be broken down and recycled sustainably.

Polypropylene is a common material found in products ranging from packaging and toys to furnishings and fashion, and is responsible for roughly 28% of the world’s plastic waste, with only 1% being recycled.

Now, fungi might be the solution to one of the world’s biggest threat: plastic.

The recalcitrant plastic, which accounts for 28% of the world’s plastic waste but only 1% of it is recycled, was biodegraded in a laboratory experiment using two common strains of fungi, Aspergillus terreus and Engyodontium album.

The polypropylene was first pre-treated with UV light or heat before being incubated for 30 or 90 days, which resulted in a reduction of 21% and 25-27%, respectively. The study was published in npj: Materials Degradation.

“Polypropylene is a common plastic used to make a huge variety of everyday products like food containers, coat hangers, and cling film, but it only has a recycling rate of only one percent, meaning it is overrepresented in plastic waste and pollution globally,” said the study’s lead author from the University of Sydney’s School of Chemical and Biomolecular Engineering, PhD student Amira Farzana Samat.

The researchers aim to develop a technique that can potentially decrease the vast quantity of plastic waste that is polluting the environment, while also enhancing our comprehension of how plastic pollution can naturally biodegrade under specific circumstances.

Plastic pollution is currently one of the most significant waste problems in the world, with a large portion of it not being properly recycled, leading to its accumulation in rivers, oceans, and landfills.

According to Mrs. Samat, an estimated 109 million tonnes of plastic pollution have accumulated in rivers, while 30 million tonnes are present in oceans. This figure is anticipated to surpass the total mass of fish in the oceans soon.

The researchers claim that polypropylene, a commonly used packaging material, is scarcely recycled due to its short lifespan and the likelihood of contamination with other materials and plastics, necessitating new recycling approaches with minimal environmental impact.

“Despite the massive scale of plastic production and consumption, there has been very little attention paid to plastics degradation under environmental conditions, and our understanding of how plastics can be degraded is limited,” said Mrs Samat’s PhD supervisor, Professor Ali Abbas from the School of Chemical and Molecular Engineering.

“One big question our result has raised is – what are the naturally occurring conditions which can fast track the degradation of plastics? We seek to further explore the role of biological processes offered by fungi and other microorganisms.”

How it works

According to the study’s co-author, Professor Dee Carter, who is an expert in mycology (the study of fungi) in the School of Life and Environmental Sciences, fungi possess remarkable adaptability and have the capability to break down almost any substance.

This ability is attributed to their production of potent enzymes that are secreted and used to break down complex substrates into simpler molecules that can be absorbed by the fungal cells.

Furthermore, the professor explains that fungi have evolved to decompose woody materials, but this characteristic can also be redirected toward other substrates. This explains why fungi are found growing on various man-made items such as carpets, painted furniture, tile grout, shower curtains, upholstery, and even car headlights.

“Recent studies sugget some fungi may even degrade some of the ‘forever chemicals’ like PFAS, but the process is slow and not yet well understood,” she said.

“There is also evidence that the amount of plastic accumulated in the ocean is less than what might be expected based on production and disposal levels, and there is speculation that some of this ‘missing’ plastic may have been degraded by marine fungi.”

Initially, polypropylene in different forms underwent treatment using one of three distinct techniques: ultraviolet light, heat, and Fenton’s reagent, which is an acidic solution of hydrogen peroxide and ferrous iron typically employed to oxidise contaminants. Following this, in a petri dish, the treated polypropylene was separately exposed to individual cultures of fungi.

The validity of bio-deterioration was then verified using microscopy methods. Although the research did not investigate how the fungi degraded or metabolised the plastic, the researchers intend to conduct further research to determine the biochemical processes involved.

What’s next?

Following their study, the researchers will focus on improving the overall effectiveness of polypropylene degradation, with the aim of increasing efficiency. After achieving this, they plan to seek investment to scale up the technology and create a small-scale pilot prototype for commercial use.

Moreover, since concluding the study, the team has identified additional microorganisms from the marine environment and utilised a comparable technique to break down marine plastic waste, with preliminary outcomes demonstrating an even higher level of degradation.

“We are quite excited about this and have started looking at different ways to improve the degradation process using these microorganisms. Watch this space,” Ms. Samat said.