Scientists at King’s College London and Rutgers University have developed an enzyme-based system that breaks down polyethylene terephthalate (PET) chemical bonds 9.2 times faster than an unmodified enzyme in water. The laboratory findings could offer a new approach to improving enzymatic polyester recycling, although the process has not yet been assessed for industrial energy requirements, environmental performance or commercial viability.

The researchers chemically modified the surface of a naturally occurring plastic-degrading enzyme, cutinase, to help it withstand high temperatures and harsh chemical conditions. They combined it with an ionic liquid designed to loosen PET’s tightly packed polymer structure, making its chemical bonds more accessible.

In laboratory tests using PET powder, the modified system maintained consistent breakdown activity over seven days, while unmodified cutinase in water lost most of its activity after approximately 36 hours. The system also carried out 9.5 times as many chemical reactions overall and enabled the recovery of pure terephthalate powder, a key building block of PET.

The researchers recovered 97.1% of the ionic liquid for potential reuse, although the enzyme itself lost its effectiveness after recovery. The findings demonstrate the potential of combining enzyme modification with ionic liquids to improve PET depolymerisation. However, the process remains at the laboratory stage, and further work is needed to establish its scalability, energy consumption, operating costs and overall environmental impact before its industrial feasibility can be determined.