Scientists Discover PETase-E3, a New Enzyme That Could Revolutionize Plastic Degradation

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  Published in Science and Technology on Friday, December 12th 2025 at 3:19 GMT by EurekAlert!
      Locale: UNITED STATES

Scientists Uncover a New Plastic‑Degrading Enzyme that Could Revolutionize Waste Management

A groundbreaking study published this week by researchers at the University of Melbourne, in partnership with the Australian National University, reports the discovery of a previously unknown enzyme that can efficiently break down polyethylene terephthalate (PET) – the most widely used plastic in beverage bottles, food containers, and countless other everyday products. The enzyme, dubbed PETase‑E3, represents a significant advance over earlier PET‑degrading enzymes and could pave the way for a new, scalable approach to tackling global plastic pollution.

The Problem: PET’s Persistent Legacy

PET has become ubiquitous because of its strength, light weight, and recyclability. Yet, the very properties that make PET attractive also make it highly durable. In landfill and marine environments, PET can persist for decades, fragmenting into microplastics that pose serious ecological and human health risks. While mechanical recycling and chemical depolymerization are options, they are energy‑intensive and often impractical on a large scale.

In the last decade, scientists have identified a handful of bacterial enzymes capable of cleaving the ester bonds that hold PET together. The most famous of these is PETase, isolated from Ideonella sakaiensis, a bacterium that thrives on PET as a sole carbon source. Although PETase can break PET under laboratory conditions, its activity is limited by low thermal stability and a narrow temperature range. Consequently, researchers have sought to discover or engineer enzymes that can operate more efficiently and under a broader range of conditions.

The Discovery

The team, led by Dr. Fiona O’Leary of the University of Melbourne’s School of Chemistry, began a targeted metagenomic survey of soil samples collected from a series of ancient landfill sites in Queensland, Australia. Using high‑throughput sequencing and bioinformatics pipelines, they screened for genes encoding potential PET‑degrading enzymes. The search yielded 34 novel enzyme candidates. After a series of biochemical tests, one candidate – PETase‑E3 – emerged as a standout performer.

PETase‑E3 displayed the ability to degrade 80% of a PET film in just 48 hours at 30 °C, a temperature well below the 55–60 °C at which most known PETases operate. Moreover, PETase‑E3 retained 70% of its activity after exposure to 60 °C, indicating remarkable thermostability.

“The enzyme’s performance at mild temperatures is what excites us the most,” Dr. O’Leary said. “It means that in practical applications, we could operate at ambient conditions, significantly lowering the energy requirements for plastic waste processing.”

How the Enzyme Works

Using X‑ray crystallography, the team solved the 3D structure of PETase‑E3 at 1.8 Å resolution. The enzyme adopts a α/β‑hydrolase fold similar to other PETases but features a distinctive active‑site pocket that allows for efficient binding of PET’s bulky terephthalate moieties. The researchers identified a series of amino‑acid substitutions that enhance the binding affinity and catalytic turnover compared to PETase.

“We engineered a few key residues to create a larger, more flexible pocket,” explained Dr. Jian Li, a structural biologist involved in the project. “This modification reduces steric hindrance and facilitates the entry of PET chains, allowing the enzyme to act more rapidly.”

In addition to its catalytic prowess, PETase‑E3 demonstrates a broad substrate range. The enzyme can also degrade partially crystallized PET, a form that has traditionally resisted enzymatic attack, as well as related polyester materials such as PET‑glycol and PET‑butyrate.

Potential Industrial Applications

The discovery of PETase‑E3 opens multiple avenues for industrial adoption:

1. Bioreactors for PET Recycling
   Small‑scale bioreactors could be designed to treat PET waste at near‑ambient temperatures, reducing energy costs compared to conventional pyrolysis or chemical recycling methods.

2. Integrated Waste‑to‑Fuel Systems
   By combining PETase‑E3 with downstream microbial consortia that ferment the hydrolysis products (terephthalic acid and ethylene glycol), companies could produce biofuels or chemical feedstocks directly from plastic waste.

3. Environmental Remediation
   Enzyme‑coated filters or biofilm reactors could be deployed in marine and landfill environments to accelerate PET degradation on a larger scale.

4. Circular Economy Models
   The enzyme’s high efficiency could make “direct recycling” of PET into high‑quality feedstock a viable, sustainable alternative to mechanical recycling, which often degrades product quality.

Challenges and Next Steps

Despite its promise, PETase‑E3 faces several hurdles before it can be commercialized:

• Scale‑Up Production
  Producing the enzyme in sufficient quantities requires optimization of recombinant expression systems. The team is currently exploring yeast and plant expression platforms that can yield high titres of active enzyme.

• Enzyme Stability in Real‑World Conditions
  While PETase‑E3 is robust at elevated temperatures, its performance in the presence of additives, dyes, and other contaminants found in PET waste streams remains to be fully characterized.

• Regulatory and Environmental Assessment
  Any enzyme‑based plastic‑degradation system must be evaluated for potential ecological impacts, especially if released into open environments.

Dr. O’Leary’s group is collaborating with industry partners, including the Australian plastic‑recycling company ReGen Solutions, to pilot a pilot‑scale reactor that treats 10 kg of PET daily. They also plan to publish a detailed kinetic model that can guide industrial process design.

Funding and Acknowledgements

The research was funded by the Australian Research Council (ARC) Discovery Project grant (DP2100000), the National Environmental Science Fund, and a philanthropic donation from the Clyde Family Foundation. The study was conducted in partnership with the University of Queensland’s Department of Microbiology and the CSIRO’s Environmental Science Institute.

Conclusion

PETase‑E3 represents a striking example of how nature’s own molecular toolkit can be harnessed to solve one of the most pressing environmental challenges of our time. By providing a robust, efficient, and versatile enzyme for PET degradation, this discovery could help close the plastic loop, reducing waste, saving energy, and mitigating the ecological harms associated with persistent plastic pollutants. The next decade will likely see significant strides as scientists, engineers, and industry stakeholders work together to translate this laboratory breakthrough into a real‑world solution.