Scientists have potentially taken the next steps towards plastic recycling by uncovering how a heat-resistant enzyme can break down one of the world’s most common plastics
The discovery could help make biological recycling methods more efficient and scalable, offering a greener alternative to traditional techniques.
Recycling PET plastics
Poly(ethylene terephthalate), better known as PET, is widely used in plastic bottles, packaging, and synthetic fibres.
While recyclable, conventional methods often require high energy input and can degrade material quality over time. Biological recycling, which uses enzymes to break down plastics into reusable components, has emerged as a promising solution.
PET becomes easier to break down at temperatures around 70°C, but most enzymes lose their structure and stop working at such high temperatures. Designing enzymes that can survive these conditions while remaining effective has been a persistent challenge for researchers.
Heat-resistant enzyme
A research team in Japan focused on a naturally occurring enzyme called cutinase, which is produced by microorganisms to break down plant surfaces. Because PET forms chemical bonds similar to those in plant cuticles, cutinases are strong candidates for plastic degradation.
The scientists studied a version of this enzyme derived from a heat-loving fungus. By analysing its structure and behaviour under high temperatures, they aimed to understand how it remains stable while still performing its function.
The study revealed that the heat-resistant enzyme has a unique structural design. Its core is highly rigid, helping it maintain stability even under intense heat.
At the same time, a flexible loop near the active site can move and adapt when interacting with molecules.
This combination appears to be key. The rigid core prevents the heat-resistant enzyme from unfolding at high temperatures, while the flexible region allows it to bind to and break down plastic molecules effectively.
The researchers also observed that the heat-resistant enzyme does not unfold all at once when heated. Instead, it undergoes a two-step process, suggesting that different parts of the structure respond differently to rising temperatures. This further supports the idea of a functional division within the enzyme.
Implications for future recycling technologies
Understanding how this balance between rigidity and flexibility works could guide the design of improved enzymes tailored for industrial recycling. By mimicking these structural features, scientists may be able to engineer enzymes that are both durable and highly active under real-world processing conditions.
Such advancements could make biological recycling more practical on a large scale, reducing reliance on fossil fuels and lowering environmental impact. Enzyme-based systems could break down plastics into their original building blocks, allowing them to be reused without loss of quality.
Sustainable solutions
Plastic pollution remains a global concern, with millions of tons of waste accumulating each year. Innovations like this highlight the potential of biotechnology to address the issue sustainably.
While more work is needed before these findings can be applied commercially, the research provides a clearer roadmap for developing next-generation recycling tools.
