How tiny fungi could help solve the world’s greatest problem: Plastic pollution

The following article is a featured submission of the Singapore Biology Reporters’ Challenge 2025.

Introduction

The rapid rise of plastic usage is a result of their lightness, durability, and low-cost production. Global plastic production reached nearly 370 million tonnes in 2020, yet only about 9% of those plastics are recycled. Plastics persist in landfills and environments thanks to their chemical structure and origins from fossilised hydrocarbons, leading to bioaccumulation and biomagnification of microplastics in ecosystems over decades. Additionally, additives like bisphenol compounds and heavy metals in plastic products may disrupt hormones and harm health. (Temporiti et al., 2022)

Many people find mould disgusting, but recent research shows that certain microscopic fungi, specifically moulds, can “digest” plastics. One such mould, Aspergillus terreus, has been discovered to be capable of breaking down polypropylene (PP), a widely used durable plastic found in packaging, automotive parts, and medical equipment (Samat et al., 2023).

Could this biological solution revolutionise how Singapore tackles the plastic waste crisis? Could this result in less incineration and transportation of plastic waste to the Semakau landfill? Is this feasible enough to prevent the Semakau landfill from being full by 2035?

The science behind this:

Professor Dee Carter, an expert in mycology (the study of fungi) in the School of Life and Environmental Sciences and co-author of the study in the article by The University of Sydney, 2023, 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 excreted and used to break down substrates into simpler molecules that the fungal cells can then absorb."

Plastics like polypropylene (PP) are made of long chains of carbon-carbon (C–C) and carbon hydrogen (C–H) bonds, with additional methyl (CH₃) side groups. This makes PP even more hydrophobic and crystalline than polyethylene, which contributes to its durability and resistance to natural degradation (Wikipedia, n.d.).

The first step required for the biodegradation of long-chain polymers with high molecular weight, such as plastics, is the weakening of the polymers’ structure. The growth of microorganisms like moulds on plastic surfaces can modify the physical properties of the plastic by creating cracks and enlarging the size of pores. Microorganisms can also chemically deteriorate plastics; one example is changing the pH of the surrounding microenvironment.

After that, the microbial exoenzymes break down the polymer into shorter chains, which are then used by cells as carbon sources. These are further broken down into water and carbon dioxide or methane to complete the mineralization process (Temporiti et al., 2022). Aspergillus terreus is known for producing enzymes like oxidases and hydrolases which speed up chemical reactions that weaken plastics’ bonds, roughen its surface, and split long polymers into smaller fragments.

Filamentous fungi grow as networks of hyphae which penetrate materials with the aid of exoenzymes and hydrophobins. This enhances adhesion to hydrophobic plastics. Their exoenzymes are non-specific, allowing them to degrade multiple types of plastic. Hydrolases (e.g., lipases, cutinases, proteases) modify plastic surfaces, increasing hydrophilicity and aiding the breakdown of plastics with hydrolysable bonds like PET and PUR. Oxidoreductases (e.g. laccases, peroxidases) then degrade plastics with stable carbon-carbon bonds (PE, PS, PP, PVC) by oxidation, followed by depolymerisation (Temporiti et al., 2022).

Aspergillus terreus is just one of the many plastic biodegrading fungi:

Notably, Pestalotiopsis microspora can even degrade plastic anaerobically, meaning it could work inside landfills: environments where most microbes are inactive. (Russell et al., 2011).

Challenges to Fungal Biodegradation

Despite the breakthrough discovery, there are various issues with its implementation:

1. Speed: Industrial streams require faster rates of biodegradation to be practical. Nonetheless, synthetic biology may help engineer strains with boosted enzyme output (Austin et al., 2018).

2. Substrate specificity: Each fungus targets specific plastics. A mixture of fungal strains or an engineered cocktail of various fungi may be needed to tackle the streams of assorted plastic waste.

3. Biosafety: Some fungi, such as Aspergillus terreus, can cause opportunistic infection in people with deficient immune systems. Furthermore, it is relatively resistant to amphotericin B, a common antifungal drug. Thus, their usage would require strict regulation. (Wikipedia, n.d.)

4. Controlled conditions: Many fungi need specific conditions (such as temperature, humidity, oxygen levels, pH, nutrients, etc.) to effectively degrade plastics. Reproducing such conditions in open landfills or oceans is incredibly difficult (Urbanek et al., 2018).

5. Economic feasibility: Setting up fungal bioreactors with the necessary growth conditions, safety protocols, as well as post-treatment steps is costly. This is because the current infrastructure for recycling plants and landfills infrastructures is not designed for biological treatment. As such, governmental support and incentives will be crucial for this to succeed.

Our future and the next step in plastic biodegradation:

Professor Dee Carter also mentions: “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.”

This observation highlights the feasibility of implementing this solution to solve the plastic waste issue. However, what really is the next step for plastic biodegradation? In an article published by the University of Sydney in 2023, Professor Abbas believes the low rate of plastic recycling globally presents a “massive plastics circularity gap”: “We need to support the development of disruptive recycling technologies that improve the circularity of plastics, especially those technologies that are driven by biological processes like in our study. It is important to note that our study did not yet carry out any optimisation of the experimental conditions, so there is plenty of room to further reduce this degradation time.”

With researchers exploring how to enhance the overall efficiency in degrading plastics, it will not be a long time before they manage to develop a small-scale pilot prototype for commercialisation. Would this be enough to solve the plastic problem once and for all, or will more problems pop up along the way? Only time will tell!

Editor’s note: The fight against plastic pollution is incessant, with many researchers turning to eco-friendlier avenues in order to tackle this issue. Along with fungi, other organisms such as bacteria and algae are being investigated as possible contenders for plastic biodegradation. However, there are still many barriers to be crossed in order to secure this method as a potential plastic-eater. Alongside the challenges mentioned in the article above, governments and corporations need to be more receptive to alternative measures of plastic degradation for real change to emerge.

References:

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2. Russell, J. R., Huang, J., Anand, P., Kucera, K., Sandoval, A.G., Dantzler, K.W., Hickman, D., Jee, J., Kimovec, F.M., Koppstein, D., Marks, D.H., Mittermiller, P.A., Núñez, S.J., Santiago, M. Townes, M.A., Vishnevtsky, M., Williams, N.E., Vargas, M.P.N., Boulanger, L., Bascom-Slack, C., Strobel, S.A. (2011). Biodegradation of polyester polyurethane by endophytic fungi. Applied and Environmental Microbiology, 77(17), 6076– 6084. https://journals.asm.org/doi/10.1128/aem.00521-11

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