Polyester textile recycling improved under industrial conditions when PET (polyethylene terephthalate), the plastic used in water bottles, food packaging and polyester clothing, was prepared to make it more accessible to enzymatic breakdown, a study has found. Stronger enzyme binding alone did not deliver the same gains, with tightly packed and highly ordered structures continuing to resist enzymatic breakdown. The results show that recycling performance depends on aligning material preparation with enzyme design in high-concentration processing environments.
- The engineered enzyme combined a heat-tolerant cutinase with a binding module to improve attachment to PET and sustain breakdown at high plastic concentrations used in industrial settings.
- Stronger attachment to highly crystalline PET did not automatically increase breakdown rates.
- Faster degradation was achieved when PET was less crystalline and more accessible, particularly under controlled conditions with managed pH and plastic concentrations of 20 per cent by weight.
- The findings have been reported in a study published in Bioresource Technology Journal by researchers from the universities of Portsmouth and Manchester.
THE STUDY: A fusion enzyme was engineered to combine a heat-tolerant cutinase with a binding module designed to improve interaction with plastic. The study examined how matching these components at similar operating temperatures and plastic structures influences performance in polyester textile recycling.
- The fusion enzyme paired a natural cutinase, which breaks down plant polyesters such as cutin, with a binding module to improve attachment to PET surfaces.
- Both components were matched to function at the same temperature and suit similar plastic structures, ensuring consistent performance under industrial-like processing conditions.
- Experiments were conducted at plastic concentrations of around 20 per cent by weight.
- The study focused on overcoming a key bottleneck in recycling by improving how enzymes interact with plastic at high concentrations.
WHAT THE DATA SHOWS: Stronger enzyme binding to PET did not consistently improve breakdown rates across tested conditions. The study showed that performance depends on the enzyme, any helper module that guides it to the plastic, and the structure of the material itself. Faster degradation was observed under conditions where material accessibility was increased, helping explain why earlier studies reported mixed results.
- Increased binding strength to highly crystalline PET did not automatically lead to faster breakdown.
- Significant gains were observed when PET structure was modified before processing, improving breakdown efficiency under controlled conditions.
- The most pronounced improvement came from pre-consumer polyester textile that was treated to reduce crystallinity and finely ground before processing.
- In such cases, the amount of useful breakdown products doubled, demonstrating the impact of material preparation on recycling outcomes.
- The findings also align with the Sabatier principle, where overly strong binding can slow reaction rates rather than improve them, explaining why excessive attachment reduces overall efficiency.
WHAT THEY SAID
By matching the enzyme with the right binding module and preparing the plastic in the right way, we can overcome a major bottleneck in plastic recycling. This isn’t just about helping the enzyme stick to the surface - it’s about making sure the chemical reaction can run efficiently at the high plastic concentrations used in industry.
— Andrew Pickford
Director, Centre for Enzyme Innovation
University of Portsmouth
