Edinburgh researchers use bacteria to turn waste plastic into paracetamol

RESEARCHERS at the University of Edinburgh have developed a method to convert waste plastic bottles into paracetamol using bacteria.

The researchers, who published their results in Nature Chemistry last month, produced the equivalent of around two tablets of paracetamol from a single polyethylene terephthalate (PET) bottle. Using a fermentation process similar to beer brewing, the researchers reprogrammed E. coli bacteria to convert terephthalic acid – derived from PET plastic – into the active ingredient in paracetamol.

The researchers hope the study can help address low plastic recycling rates. Despite being inherently recyclable, PET bottles often end up in landfills or the ocean due to inefficiencies in the recycling system. In 2020, around 347,000 t of plastic bottles were collected for recycling in the UK, according to a survey from by trade organisation RECOUP. However, this figure is estimated to be 15–50% higher than the amount actually recycled, as significant quantities are discarded during sorting and cleaning.

Campaigners also argue that PET recycling, which typically results in more plastic products, does little to address the underlying issue of global oversupply. Stephen Wallace, chair of chemical biotechnology at the University of Edinburgh and an author on the latest paper, said: “This work demonstrates that PET plastic isn’t just waste, or a material destined to become more plastic – it can be transformed by microorganisms into valuable new products, including those with potential for treating disease.”

The researchers also hope their work can help address emissions in the pharmaceutical industry. Industrial paracetamol manufacturing is based on the acetylation of para-aminophenol. According to a study published last year in the British Journal of Anaesthesia, a 1 g oral dose of paracetamol in tablet form has a carbon footprint of 38 gCO2e. This increases to up to 628 gCO2e for intravenous administration. The Edinburgh team said their method, demonstrated at room temperature, could be carried out with “virtually no carbon emissions”. The researchers reported that the reaction was complete in under 24 hours, with paracetamol making up 90% of the final product.

Wallace told TCE the research marked an “exciting first step toward turning plastic waste into valuable medicines.

“With further work to scale up and improve the efficiency of the fermentation process, we expect this yield could increase significantly.”

Wallace said that scaling success would depend on life cycle assessments, techno-economic analysis and safety assessments compared to the conventional process of industrial paracetamol manufacturing. He told TCE: “Given how carbon-intensive and polluting the existing method is, we anticipate this comparison will strongly favour the biobased alternative.

“While the concept is promising at this early stage, substantial process engineering and regulatory efforts will be essential to bring it to market.”

The research was jointly funded by the state funding agency UK Research and Innovation (UKRI) and pharmaceutical company AstraZeneca. Ian Hatch, head of consultancy at the University of Edinburgh’s commercial arm, Edinburgh Innovations, encouraged more private sector collaboration in future research, adding: “Engineering biology offers immense potential to disrupt our reliance on fossil fuels, build a circular economy and create sustainable chemicals and materials.”