Single-atom change doubles PET plastic breakdown speed

Summary

Researchers at ANU demonstrated that changing a single atom in the structure of the PETaz enzyme (converting a C–H pair to nitrogen via azatryptophan substitution) nearly doubles the rate of PET degradation. This modification eliminates the long-standing activity-stability trade-off in enzyme engineering while maintaining the enzyme's thermal stability.

Why it matters

Over 350 million tons of PET waste are generated globally each year. Therefore, any significant acceleration in enzymatic recycling is of great importance. The study also proves that non-standard amino acids can be used as atomic-level tuning tools. This opens up a broader design space for industrial enzymes, biofuels, and therapeutic proteins beyond the 20 natural building blocks.

Highlights

• A single-atom C→N change in tryptophan nearly doubles PETaz catalytic speed without compromising heat resistance
• A new fluorescence analysis method, 'PETra', reduces enzyme variant screening from days to minutes
• The study was published in Angewandte Chemie International Edition; first author Dr. Elwy Abdelkader, co-author Prof. Thomas Huber

Critical take

The paper's hasty language ('microscopic surgery', 'degrading PET in half the time') overshadows the evidence. This is a laboratory-scale enzyme variant. The text does not mention the cumbersome hurdles of industrial implementation. Issues such as access to the substrate in real waste streams, enzyme costs on a ton scale, and competition with existing mechanical and chemical recycling methods are ignored. The emphasis on '350 million tons' also overlooks the fact that only a small fraction of this waste may be suitable for enzymatic processing.