Researchers Develop Enzyme to Combat Polyurethane Pollution

A team of researchers has developed a new enzyme capable of breaking down polyurethane, a polymer widely used in products like foam cushioning. This breakthrough addresses a significant issue in plastic pollution, where traditional recycling methods struggle with the diverse chemical bonds present in various plastics. The new enzyme integrates effectively with existing industrial processes, allowing the conversion of polyurethane back into its basic building blocks for reuse.

According to the research published in the journal Science, approximately 22 million metric tons of polyurethane were produced in 2024. The complexity of the polymer, characterized by urethane bonds linking nitrogen, carbon, and oxygen atoms, makes its breakdown challenging. Current methods often involve the use of diethylene glycol, which can partially degrade these polymers but typically leaves behind hazardous waste.

The research team aimed to identify an enzyme that could work alongside diethylene glycol to enhance the breakdown process. They began by testing existing enzymes known for their ability to degrade polyurethanes. Out of 15 enzymes evaluated, only three displayed satisfactory activity, but none effectively converted the polymer into its constituent materials.

To overcome this limitation, the researchers turned to advanced protein design tools. They utilized a neural network called Pythia-Pocket, which predicts interactions between amino acids and potential binding sites. This was combined with another network, Pythia, to assess the stability of protein structures. The goal was to find a candidate enzyme that maintained both catalytic activity and structural flexibility.

The team also developed a software tool named GRASE (graph neural network-based recommendation of active and stable enzymes) to assist in their search. This innovative approach resulted in the identification of 24 proteins, of which 21 demonstrated catalytic activity. Notably, eight of these outperformed the best-known enzyme, with one exhibiting activity 30 times greater.

When combined with diethylene glycol and heated to 50°C, the newly designed enzyme achieved remarkable results. It successfully broke down 98 percent of polyurethane in just 12 hours. Additionally, the enzyme exhibited sufficient stability to process fresh batches of polyurethane twice more before its activity diminished.

Transitioning from laboratory tests to larger-scale applications demonstrated that over 95 percent of the material was converted back into its constituent components. The researchers emphasized that their approach not only focuses on structural similarities but also incorporates functional aspects, such as stability and amino acid interactions.

This innovative enzyme represents a significant step forward in addressing plastic waste. The findings suggest that advanced protein design tools may offer new avenues for developing functional proteins, potentially revolutionizing recycling processes for various polymers in the future. The study is set to impact the ongoing efforts to mitigate plastic pollution globally.

For further details, refer to the research published in Science, DOI: 10.1126/science.adw4487.