Scientists have created a new enzyme that can help recycle polyurethane, a common plastic used in foam cushions and shoe soles. This enzyme can turn polyurethane foam into reusable chemicals in just about 12 hours. It’s a big step forward in tackling plastic waste, especially for tough materials like polyurethane that are hard to break down.

Why Polyurethane Is So Hard to Recycle

Polyurethane is a versatile plastic with complex chemical bonds. It’s made up of chains linked by urethane bonds, which involve nitrogen and carbon atoms. These chains often cross-link and have bulky structures, making it difficult for natural enzymes to digest them. Currently, the main method to break down polyurethane involves heating it with chemicals like diethylene glycol, which only partially dissolves the material and creates messy chemicals that can’t be reused easily. Usually, such waste is incinerated, which isn’t great for the environment.

Developing a Better Enzyme with AI Tools

Researchers started by testing 15 enzymes known to break down plastics. Only three showed some activity, but none could fully break down polyurethane into its building blocks. They focused on the most promising enzyme and used public protein databases to find related proteins. But these didn’t work well either. So, they turned to artificial intelligence to find better options.

They used a neural network called Pythia-Pocket, which predicts how proteins interact with chemicals. Combined with another tool called Pythia that forecasts protein stability, they developed a program named GRASE. This tool recommended new enzyme candidates by balancing structural stability and flexible binding to the tough polyurethane chains.

Impressive Results and Environmental Impact

Out of 24 top enzyme candidates suggested by GRASE, 21 showed some ability to catalyze the breakdown of polyurethane. Eight of these enzymes were much better than the natural ones, with the top performer being 30 times more active. When combined with heat and diethylene glycol, the new enzyme was over 450 times more active than the best natural enzyme. It could degrade 98% of polyurethane in 12 hours and remained stable enough to be reused a few times.

Scaling up to larger amounts, the enzyme still broke down over 95% of the foam into its original materials. This breakthrough could lead to more sustainable recycling methods, turning waste into useful raw materials rather than hazardous waste. The team emphasizes that their approach goes beyond just protein structure, considering how proteins function and interact with materials. This could open new doors for designing enzymes to solve other tough recycling challenges and help reduce plastic pollution.

Inspired by

• https://arstechnica.com/science/2025/10/polyurethane-is-the-latest-polymer-broken-down-by-designer-enzymes/

Sources

• conde.digital
• cnevids.com
• github.com
• doi.org