E. coli Converts Plastic Waste Into Paracetamol

Can plastic waste become medicine?

Researchers at the University of Edinburgh have shown that engineered Escherichia coli (E. coli) can convert molecules from recycled plastic bottles into paracetamol.

The study, published in Nature Chemistry, demonstrates a new low-emission method to produce this common painkiller using waste plastic instead of fossil fuels.

Why plastic waste and paracetamol are a chemical challenge

More than 450 million tonnes of plastic are made each year, with a lot being polyethylene terephthalate (PET) – the type used for drinks bottles and food packaging. Although PET is strong, lightweight and cheap, it’s also hard to reuse without downgrading it. Most PET recycling still leads to more plastic or ends up in landfills and the ocean.

At the same time, making simple medicines like paracetamol still relies on fossil fuels. The process starts with phenol – a chemical derived from crude oil – and uses a lot of energy. It’s efficient but not sustainable.

Recently, scientists have started combining the tools of chemistry and synthetic biology to make chemicals within living microbes. The idea is to train genetically engineered bacteria to do industrial chemistry using waste materials, such as PET. Some progress has been made, but building new reactions into cells is difficult. Most known chemical reactions don’t work inside living systems.

The Lossen rearrangement – a simple reaction that turns certain carboxylic acids into amines – is one of these chemical reactions. Until now, it had never been shown to work inside cells or be tied to metabolism.

The goal of the new study was to test whether this chemical reaction, normally used in the lab, could work inside bacteria and be used to turn plastic waste into a pharmaceutical product.

Engineering E. coli to make paracetamol from PET

The team started by testing whether E. coli could handle a Lossen rearrangement reaction inside the cell. They used strains of E. coli that couldn’t make para-aminobenzoic acid (PABA), an essential compound for growth, and fed them a molecule designed to rearrange into PABA.

The bacteria started growing, confirming the reaction was happening inside the cells, without harming them.

The reaction was catalysed by phosphate, a compound already present in the growth medium, making it fully compatible with living cells. 

The researchers then made the same starting molecule from plastic waste. Specifically, from terephthalic acid, a compound derived from post-consumer PET bottles.

The process took two steps. When the PET-derived molecule was fed to the engineered E. coli, it again supported growth, revealing that plastic waste could be converted into a biologically useful material. The conversion took place under mild, fermentation-like conditions at room temperature, with no need for high pressure or toxic reagents.

To push things further, the researchers added two genes to the bacteria: one from a fungus and another bacterium. These genes encode for enzymes that turn PABA into paracetamol.

With these tools in place, E. coli made paracetamol from the PET-based starting material at yields of up to 92%, including a yield of up to 83% when starting from actual plastic waste.

The whole reaction happened in under 48 hours, with no detectable toxic byproducts.

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What does this mean for plastic recycling and drug manufacturing?

Instead of relying on fossil fuels, the results show that paracetamol could be made using post-consumer PET. The process uses less energy, avoids toxic byproducts and could reduce emissions from pharmaceutical manufacturing.

This is the first time a non-enzymatic reaction, like the Lossen rearrangement, has been shown to work inside a living cell and link directly to metabolism – opening the door to designing new cell-based processes using tools from synthetic chemistry, not just biology.

“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,” said lead author Dr. Stephen Wallace, a professor of chemical biotechnology at the University of Edinburgh.

However, the system hasn’t been scaled to industrial levels. The plastic must still be broken down in a separate step before fermentation starts. For now, it’s more of a framework than a finished solution.

The team is now working on scaling the process in bioreactors, building in the plastic degradation step and applying the chemistry to other targets. They also plan to run life cycle assessments to measure their real-world environmental impact.

“We are bringing in exceptional companies like AstraZeneca to work with Stephen and others at the University to translate these cutting-edge discoveries into world-changing innovations,” said Ian Hatch, the head of business development at the College of Science and Engineering in Edinburgh Innovations.

“Engineering biology offers immense potential to disrupt our reliance on fossil fuels, build a circular economy and create sustainable chemicals and materials, and we would invite potential collaborators to get in touch,” he added.

Reference: Johnson NW, Valenzuela-Ortega M, Thorpe TW, et al. A biocompatible Lossen rearrangement in Escherichia coli. Nat Chem 2025. doi: 10.1038/s41557-025-01845-5

This article is a rework of a press release issued by the University of Edinburgh. Material has been edited for length and content.