PET Degrading Enzymes Have Potential to Reduce Plastic Pollution

Every day, people rely on plastic products. From containers and bottles to bags and textiles, plastic permeates as a convenience through modern lifestyles – and as a persistent problem in pollution. The environmental risk of plastics is a significant problem scientists are working to solve, particularly as the material breaks down into microplastics and infiltrates ecosystems. This poses a global threat to the health of animals, plants, and humans.

The polymer polyethylene terephthalate (PET) in plastic products poses a significant challenge due to its resistance to degradation. Material and chemical scientists are working toward innovative solutions to recycle plastic and PET to reduce plastic pollution in the world’s natural environments.

Various bio-based methods using enzymes are emerging as promising approaches to degrading PET by repurposing the material while retaining its high quality and valuable characteristics for plastic products. Robust analytical techniques are essential to propelling this work forward and ensuring effective and impactful plastic recycling in a sustainable circular economy.

What is PET and why does it challenge plastic recycling efforts?

PET is a polymer widely used in everyday plastic products, such as bags from the grocery store, water bottles, and food packaging.

PET’s qualities make it a popular material for plastic products, such as its high durability and low manufacturing cost. However, these qualities also make it a widespread pollutant that cannot degrade. It invades natural environments, such as the ocean, and becomes concentrated in fish and other seafood that people consume.

More than 30 million tons of PET is produced annually, making it a prime target for novel plastic recycling approaches.

A team of resarchers from Toulouse Biotechnology Institute at the Université de Toulouse and biotechnology company Carbios in France addressed the plastic recycling challenge posed by PET. The team identified a promising enzyme mutant called Leaf-branch Compost Cutinase (LCC) that efficiently degrades PET.

This mutated form of LCC also outperformed other tested enzymes and preserved the basic components of PET. It still perfomed as a high-quality plastic when repurposed into a new product. Because of these abilities, the scientists concluded that the LCC enzyme is a promising solution to breaking down plastic and limiting the pollution produced from plastic product manufacturing, everyday use, and disposal. This finding opens up the potential for enzyme studies as solutions to plastic pollution.

Identifying and Optimizing an Efficient PET Degrading Enzyme Using NMR Technology

The scientists rigorously tested and engineered proteins, including LCC, to present a mutated enzyme with optimal characteristics that solved PET degradation challenges. They performed in-depth NMR studies using Bruker TopSpin software to identify and analyze data about the features of LCC and its mutants for desirable performance in unfolding PET.

The team expressed and purified proteins of interest and characterized the molecular structures including dynamics and binding sites by means of NMR. They also analyzed calcium chemical shift perterbations, thermal stability, and acidic interactions through titration.

These experiments revealed the most effective binding sites where the enzyme links and unravels PET, and improves thermostability. This information helped them identify an LCC enzyme candidate they dubbed PETase. This would be the optimal solution for PET degradation and recycling at an industrial scale.

PETase was stabilized through multiple calcium binding sites and functional at high temperatures where PET would begin unfolding. This optimized PET-degrading enzyme will provide valuable insight and inspiration for future directions to study enzyme dynamics and function in plastic recycling.

NMR is a unique and powerful technique for chemical analysis ranging from basic identification and quantification of substances to molecular structure elucidation and dynamics investigation. With a range of NMR systems – from cost-optimized benchtop devices to high-performance floor-standing instruments – Bruker provides a powerful solution portfolio for comprehensive value chain coverage from product innovation to manufacturing. Powered by our industry-leading analysis and acquisition software TopSpin, Bruker NMR systems enable organizations to achieve a Distributed Laboratory Topology (DLT) in which expertise, methods, and data can be easily and quickly shared between different stages in the value chain and different locations.

Next Steps for Plastic Recycling and the Circular Economy

This study is focused on the NMR approach to revealing and optimizing enzymes that can break down plastic by following LCC through its mutations toward improved PETase performance. The need for effective methods that enable advanced data acquisition and analysis of a complex relationship between enzymes and polymers is underscored by plastic pollution. An in-depth understanding of the chemical dynamics of these materials moves this research toward the goal of establishing novel plastic recycling methods to support a circular economy.

Bruker’s TopSpin NMR software amplifies Bruker NMR instruments with smart acquisition and advanced processing of data in a usable platform. This setup allows scientists to focus on the essential part of their research. Its wide range of capabilities for various workflows enabled these researchers to identify and optimize a novel PET degrading enzyme.

With the ability to not only break down PET, but also preserve its monomers to reconstitute it back into a high-quality plastic material, the PETase described in the publication has the potential to cut down waste and use of resources in the plastic lifecycle. This directly contributes to the circular economy school of thought, and has potential for real-world impacts on the health of the world’s ecosystems and people.

While more research is needed to translate this potential solution into an industry-scale application, the evidence points toward a more environmentally conscious future when dealing with plastics. In transforming society’s relationship with plastic from linear to circular, scientific studies such as this provide a foundation for exploring future sustainable solutions to plastic pollution.

Sources:

Charlier, Cyril, et al. “An NMR Look at an Engineered PET Depolymerase.” Biophysical Journal, vol. 121, no. 15, Aug. 2022, pp. 2882–94, https://doi.org/10.1016/j.bpj.2022.07.002 . Accessed 20 Feb. 2023.