26 Oct 2023 — Scientists have developed artificial proteins capable of degrading PET microplastics and nanoplastics while reducing them to their essential components, which would allow them to be recycled. 

For the project, scientists from the Barcelona Supercomputing Center — Centro Nacional de Supercomputación (BSC-CNS), Spain, worked together with research groups from the Institute of Catalysis and Petrochemistry of the CSIC (ICP-CSIC) and the Complutense University of Madrid. 

The researchers used a defense protein from the strawberry anemone (Actinia fragacea), to which they added the new function after design using computational methods. The results are published in Nature Catalysis. 

Víctor Guallar, ICREA professor at the BSC and one of the authors of the work, says what the team is doing is like “adding arms to a person.” 

“These arms consist of just three amino acids that function as scissors capable of cutting small PET particles. In this case, they have been added to a protein from the anemone Actinia fragacea, which in principle lacks this function and which in nature functions as a cellular drill, opening pores and acting as a defense mechanism.”

The developed aritificial proteins can degrade PET microplastics and make them recyclable.Boosted PET degradation
Machine learning and supercomputers such as the BSC’s MareNostrum 4 used in this protein engineering allow “predicting where the particles are going to join and where we must place the new amino acids so that they can exert their action,” says Guallar. 

The results indicate that the new protein can degrade PET micro- and nanoplastics with “an efficiency between five and ten times higher than that of PETases currently on the market and at room temperature,” explains Guallar. Other approaches require temperatures above 70 degrees Celsius to make the plastic more moldable, which leads to high carbon dioxide emissions and limits its applicability.

In addition, the pore-like structure of the protein was chosen because it allows water to pass through and can be anchored to membranes similar to those used in desalination plants. 

Manuel Ferrer, research professor at the ICP-CSIC and responsible for the study, says the structure would facilitate its use in the form of filters, which “could be used in purification plants to degrade those particles that we do not see, but which are very difficult to eliminate and which we ingest.”

A design for recyclingThe newly developed proteins allow for enhanced PET recycling.
Another advantage of the new protein is that two variants were designed depending on where the new amino acids are placed. The result is that each gives rise to different products.

“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, who is working on her doctoral thesis at ICP-CSIC.

The current design could already have applications, according to the researchers, but “the flexibility of the protein, like that of a multi-purpose tool, would allow new elements and combinations to be added and tested,” explains Dr. Sara García Linares, from the Complutense University of Madrid, who has also participated in the research.

“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,” adds Ferrer.

Guallar concludes: “Computational methods and biotechnology can allow us to find solutions to many of the ecological problems that affect us.”

Edited by Natalie Schwertheim

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