How microbes could help solve the world’s plastic pollution crisis

With conventional waste management systems falling short, many scientists are turning to nature for innovative solutions to the issue of plastic waste. One promising avenue is microbial degradation: harnessing the natural abilities of certain bacteria and fungi to break down plastics in ways that current technologies cannot.

These microbes produce specialised enzymes (proteins that carry out chemical reactions) capable of breaking the long, carbon-rich chains of molecules that form the backbones of many plastic polymers. They effectively use plastic as a food source.

Historically, scientists looking for plastic-degrading microbes have focused on plastic-polluted environments such as landfills and contaminated soils. These are logical starting points, as prolonged exposure to synthetic polymers may encourage the growth of organisms that are capable of using these materials as a food source. This trend has also been observed with other environmental pollutants including oil and pesticides.

This approach has led to the discovery of several promising candidate microbes that can degrade plastic. Among the most famous examples is Ideonella sakaiensis, a bacterium identified near a plastic bottle recycling facility in Japan.

It can completely degrade polyethylene terephthalate (PET), the plastic most commonly used in bottles and food packaging. It breaks PET into its (environmentally benign) building blocks. These can then be used as food by I. sakaiensis and other organisms.

But plastic-degrading microbes haven’t evolved this capability in response to plastic pollution. Instead, scientists are discovering and repurposing metabolic functions that already exist in nature. The potential for microbes to break down plastic long predates the invention of plastics themselves.

Many microbes already have the ability to decompose natural polymers such as cellulose (plant fibres), chitin (found in fungi and insects) and cutin (found on the surfaces of leaves). These naturally occurring materials share structural and chemical similarities with synthetic plastics. This overlap allows microbes to repurpose existing enzymes to tackle synthetic substances.

My team’s recent research, published in the journal Polymer Degradation and Stability, supports this idea. From unpolluted environments rich in natural polymers (a peat bog and domestic compost), we identified two bacterial strains, Gordonia and Arthrobacter, that degraded polypropylene and polystyrene by nearly 23 per cent and 19.5 per cent, respectively, in just 28 days. Crucially, this occurred without any pretreatment, which is often required to make plastics more susceptible to microbial attack.

While these numbers may seem modest, they are among the highest biodegradation rates ever recorded for these plastics. This suggests that we don’t have to stick to polluted sites. It’s possible that we could find microbes with excellent plastic-degrading potential anywhere.

This aligns with another fascinating study showing that waxworms (Galleria mellonella) can eat plastic bags, thanks to specific gut microbes. Waxworms do not naturally consume plastic, they are common pests in beehives where they feed on honeycomb. But, structurally, honeycomb is similar to polyethylene, the main component of plastic bags.

Drowning in plastic?

These advances are exciting because they show how nature can offer us tools to deal with the plastic problem we’ve created.

Plastic is one of the most pervasive materials on Earth. Lightweight, durable, cheap to produce and infinitely versatile, it permeates nearly every aspect of modern life. In critical applications such as medical devices and equipment, its presence is not just convenient but essential. Lives often depend on it.

But in the wrong context, the qualities that make plastics so useful and durable become their greatest flaw. Most plastics do not readily biodegrade, instead accumulating in natural environments, gradually fragmenting into microplastics that can persist for centuries. This poses a long-term threat to nature and human health.

Global plastic production now exceeds 460 million tonnes annually. Up to half of this is estimated to be single-use items, often used for only a few moments before being discarded.

While diligent users of recycling facilities might assume that most of our plastic is indeed recycled, the reality is sobering: the global recycling rate for plastics is only nine per cent.

Around half ends up in landfills, while around one-fifth is incinerated, and another fifth is mismanaged so it’s not recycled, incinerated or securely contained. That means it can end up in rivers, lakes and oceans. The result: a planet drowning in synthetic waste.

As plastic production and disposal continue to outpace our ability to manage it, the need for innovative, sustainable solutions is urgent. Recognising this, the UN’s ongoing negotiations for a global plastics treaty aims to build a more circular economy for plastics and end plastic pollution by 2040.

While challenges remain in enhancing the biodegradation capabilities of microorganisms to make them a viable solution for large-scale waste management and environmental remediation, progress is steadily being made.

Advances in microbial engineering, enzyme discovery and environmental microbiology are paving the way towards more efficient and scalable plastic biodegradation systems. With continued research and investment, what was once a distant possibility is now a realistic and promising component of a broader strategy to combat plastic pollution.

Julianne Megaw, Lecturer in Microbiology, Queen's University Belfast

This article is republished from The Conversation under a Creative Commons license. Read the original article.