The durability of modern plastics renders these materials crucial for many packaging, construction, medical device design and other industrial applications. Their seemingly indestructible nature also poses an environmental nightmare, as discarded plastic is difficult to decompose and can contaminate ecosystems and food chains over long time horizons. Fortunately, an enzyme variant developed at the University of Texas at Austin can degrade environmentally persistent plastics that typically take centuries to degrade in just a matter of hours to days.

Enzymes previously developed to quickly break down polyethylene terephthalate (PET) plastics are limited by an inability to function well at low temperatures and different pH ranges, slow reaction rates and poor performance when applied to untreated plastic waste. The researchers sought to address these performance shortfalls with a machine learning model developed to predict which mutations in a PETaseA new enzyme quickly degrades PET plastics. Source: University of Texas at Austin enzyme would afford it these capabilities. This involved closely studying a range of PET plastic products, including containers, water bottles and fabrics, and then using the model to design and engineer a new and improved enzyme dubbed FAST-PETase (functional, active, stable and tolerant PETase).

The newly minted enzyme described in Nature proved superior at breaking down PET plastics at temperatures between 30° C and 50° C (86° F and 122° F) and at a range of pH levels. More than 51 different post-consumer plastic containers, five different polyester fibers and fabrics and water bottles were almost completely degraded in the space of a week, and in some experiments broke down. Some plastic materials were also decomposed in as little as 24 hours, and a closed-loop PET recycling process, in which FAST-PETase was used to break down the plastics and then the recovered monomers were used to chemically reconstruct the material, was also demonstrated.

The researchers plan to scale up enzyme production to prepare for industrial and environmental applications.