Approximately 400 million tonnes of plastic are produced worldwide each year, and this number is increasing by approximately 4% each year. Emissions resulting from their production are one of the factors contributing to climate change, and their widespread presence in ecosystems causes serious environmental problems.

One of the most used is PET (polyethylene terephthalate), found in many packaging and beverage bottles. Over time, this material breaks down into smaller particles called microplastics, exacerbating environmental problems. PET currently accounts for more than 10% of global plastic production, and recycling is rare and inefficient.

Now, scientists from the Barcelona Supercomputing Center – Centro Nacional de Supercomputación (BSC-CNS) together with research groups from the CSIC Institute of Catalysis and Petrochemistry (ICP-CSIC) and the Complutense University of Madrid (UCM) have developed artificial proteins. It can break down PET microplastics and nanoplastics and reduce them to their basic components, allowing them to be broken down or recycled.

They used a protective protein from the strawberry anemone (Actinia fragacea) and added a new function to it after designing it using computational methods. The results are published in the journal Nature Catalysis.

extension of nature

“What we’re doing is like adding a weapon to a person,” explains Victor Guallar, ICREA professor at BSC and one of the paper’s authors. These arms consist of just three amino acids that act as scissors that can cut small PET particles. In this case, they were added to a protein from the anemone Actinia fragacea, which in principle does not have this function and “acts as a cell-piercing, pore-opening and defense mechanism” in nature, the researcher explains.

Machine learning and supercomputers like BSC’s MareNostrum 4 used in this protein engineering allow us to “predict where particles will bind and where we need to put new amino acids to make them work,” Guallar says. The resulting geometry is very similar to that of the PETase enzyme from the bacterium Idionella sakaiensis, which can break down this type of plastic and was discovered at a packaging recycling facility in Japan in 2016.

The results show that the new protein can degrade PET micro- and nanoplastics “with an efficiency 5 to 10 times higher than currently commercially available PETases and at room temperature,” Guallar explains. Other approaches require temperatures above 70 °C to make the plastic more moldable, resulting in high CO emissions₂ and limits its application.

It was also chosen because the protein’s pore-like structure is permeable to water and can bind to membranes similar to those used in desalination plants. This would facilitate its use in the form of filters that “could be used in treatment plants to remove particles that we cannot see, but are very difficult to remove and that we ingest,” says ICP-CSIC research professor Manuel Ferrer. and is also responsible for research.

A design that allows cleaning and/or recycling

Another advantage of the new protein is that two variants have been developed depending on the location of the new amino acids. After all, each of them produces different products.

“One option breaks down PET particles better so that they can be used for separation in wastewater treatment plants. Another gives rise to the initial components required for the process. In this way we can refine or recycle depending on the needs,” explains the CSIC Institute of Catalysis and Petrochemistry Laura Fernández López, who is working on her PhD at (ICP-CSIC).

The current design may already have applications, according to the researchers, but Dr. Sara García Linares explains: “The flexibility of the protein will allow new elements and combinations to be added and tested, like a multi-purpose tool.” She participated in the study in Madrid.

“By combining the potential of naturally produced proteins and machine learning with supercomputers, we want to create new designs that will allow us to create a healthy environment without plastic,” says Ferrer.

“Computational methods and biotechnology can enable us to find solutions to many problems