Scientists Discover Enzyme That Breaks Down Stubborn Polyurethane Plastic

An international team of scientists has uncovered how a newly studied enzyme can break down polyurethane, a widely used but difficult-to-recycle plastic. Their findings reveal the molecular structure and reaction process behind the enzyme's ability to degrade this persistent material. The discovery opens doors for more sustainable plastic waste solutions in industries reliant on polyurethane. The enzyme, named Aes72, targets urethane bonds within polyurethane—a process that had previously eluded researchers. Using advanced structural biology, the team mapped its crystal structure at a high resolution of 1.80 Ångströms. This detailed view allowed them to understand how Aes72 interacts with the plastic's complex molecular chains.

Further analysis through multiscale quantum mechanics and molecular mechanics (QM/MM) simulations uncovered a four-step reaction cascade. This cascade enables the enzyme to hydrolyse polyurethane efficiently. However, thermoset polyurethane foams, known for their tightly cross-linked structure, remain particularly resistant to enzymatic breakdown. To improve performance, the researchers engineered a modified version of Aes72, called F276A/L141I. Testing showed this variant doubled catalytic efficiency on model substrates. It also demonstrated strong chain-scission activity, significantly reducing the mass of polyurethane samples during experiments. Polyurethane ranks as the fifth most produced synthetic polymer worldwide, yet conventional recycling methods struggle with its durability. Industries such as furniture, mattress, and insulation manufacturing—as well as automotive and footwear sectors—could benefit most from this enzyme. Major polyurethane producers like BASF, Covestro, and Dow Chemical may also adopt the technology to process waste streams more sustainably.

The study provides a foundation for developing more effective biocatalysts tailored to polyurethane recycling. By enabling degradation under mild, solvent-free conditions, the engineered enzyme offers a greener alternative to traditional methods. This shift could reshape waste management practices for one of the most challenging plastic materials in use today.