Spanish researchers created a new protein capable of degrading PET microplastics, according to a study published in Nature Catalytics.
We produce around 400 million tons of plastic worldwide every year. The emissions from their manufacture are one of the main elements contributing to climate change, and their presence in different ecosystems leads to serious ecological issues.
One of the most common types of plastic is PET (polyethylene terephthalate), which is used in packaging and bottles. Over time, PET wears down into smaller particles to produce microplastics, further aggravating environmental problems. However, PET recycling is insufficient.
Now, a team of researchers from the Barcelona Supercomputing Center – Centro Nacional de Supercomputación (BSC-CNS), in collaboration with groups from the Institute of Catalysis and Petrochemistry of the CSIC (ICP-CSIC) and the Complutense University of Madrid (UCM), have created an artificial protein that can degrade PET and reduce it to its essential components, which can then be recycled. They started with a protein from the strawberry anemone (Actinia fragacea), which can already open pores, then altered its design to add new functions. “What we are doing is something like adding arms to a person,” explains Víctor Guallar, ICREA professor at the BSC and one of the authors of the work. As the researchers explained, the arms are just three amino acids that can work as scissors to cut small PET particles.
Computer models used in this protein engineering allow researchers to predict “where the particles are going to join and where we must place the new amino acids so that they can exert their action,” said Guallar. The resulting protein is similar to a PETase enzyme from the bacterium Idionella sakaiensis, which can degrade this type of plastic but is more efficient.
The new protein can degrade PET micro- and nanoplastics with “an efficiency between 5 and 10 times higher than that of PETases currently on the market and at room temperature,” explained Guallar. Other methods need high temperatures to make the plastic more mouldable, which leads to increased CO2 emissions and limits its applicability.
Furthermore, the new protein has a porous structure and can be attached to membranes similar to those used in desalination plants. This would mean they can potentially be used in the filters in “purification plants to degrade those particles that we do not see, but which are very difficult to eliminate and which we ingest,” said Manuel Ferrer, Research Professor at the ICP-CSIC.
The team used the same approach to design two proteins with different functions for the arms. “One variant breaks down the PET particles more thoroughly, so it could be used for degradation in sewage treatment plants. The other gives rise to the initial components needed for recycling. In this way, we can purify or recycle, depending on the needs,’ explains Laura Fernández López from the CSIC’s Institute of Catalysis and Petrochemistry (ICP-CSIC).
The team is convinced that the flexibility of the protein means new elements can be added in the future. “What we are looking for is to combine the potential of proteins provided by nature and machine learning with supercomputers to produce new designs that allow us to achieve a healthy zero-plastics environment,” concluded Ferrer.
Robles-Martín, A., Amigot-Sánchez, R., Fernandez-Lopez, L. et al. Sub-micro- and nano-sized polyethylene terephthalate deconstruction with engineered protein nanopores. Nat Catal (2023).https://doi.org/10.1038/s41929-023-01048-6