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Enzymatic recycling has gained traction in recent years as a greener alternative to traditional plastic recycling techniques, which often rely on energy-intensive mechanical or chemical processes. Enzymes can selectively break down polymers like PET—commonly found in bottles and food packaging—into their basic building blocks.

In this new study, scientists have introduced an innovative strategy to trap these enzymes within nanoscale protein compartments produced naturally by bacteria, simplifying their use and extending their functional lifespan. The work is in the Journal of Hazardous Materials.

One of the major barriers to industrial enzymatic recycling is the cost and complexity of producing and recovering the enzymes. Traditional immobilization methods involve multiple steps, including enzyme purification and attachment to solid carriers.

The system developed by the research team overcomes this by embedding the enzyme directly inside nanospheres during its expression in E. coli, using a single-step process that combines production, immobilization, and stabilization. This dramatically reduces costs and enhances reusability.

The technology builds on IC-Tagging, developed by Prof. José Manuel Martínez Costas and his group at CiQUS. It uses a viral protein, muNS-Mi, which self-assembles into nanostructures within bacterial cells.

Enzymes tagged with a short IC-sequence are spontaneously recruited into these compartments, resulting in fully functional, immobilized enzymes straight from the host cell—no chromatography or additional carriers needed. While IC-Tagging has previously been used for other biocatalysts, this is the first time it has been applied to a high-performance PET hydrolase.

The team used a genetically optimized version of the LCC enzyme, known for its high efficiency in PET degradation. Their system successfully broke down real post-consumer plastic samples—including food trays and lab packaging—achieving over 90% depolymerization in under 72 hours. Moreover, the same batch of enzyme could be reused for two consecutive reactions with minimal loss of activity.

"These results go beyond what has been achieved so far with immobilized enzymes at lab scale," says Adrián López Teijeiro, first author of the study. "Our system offers a powerful tool to support the industrial deployment of enzyme-based PET recycling and advance the circular economy for plastics."

The work is part of the PETzyme project and coordinated by Gemma Eibes (CRETUS) and José Martínez Costas (CiQUS). The team is currently working to scale up the method and explore its potential with other industrially relevant enzymes in areas such as biocatalysis, waste processing and sustainable materials.