Scientists invent biotech that turns plastic waste into commonly used painkillers

Paracetamol tablets are among the world’s most-used medicines, but their production typically depends on dwindling fossil fuels.

A research team led by the University of Edinburgh has now demonstrated an alternative: re-engineering the gut bacterium Escherichia coli. In less than a day, it can convert the building blocks of discarded bottles into the active ingredient of the drug.

The proof-of-concept hints at a future in which common medicines – and many other chemicals – could be brewed sustainably. The source? Mountains of single-use plastic that currently clog landfills and oceans.

Most plastic goes unrecycled

Most disposable water and soft-drink bottles consist of polyethylene terephthalate, or PET. Each year, the world produces more than 350 million tons of the material, and only a minority is recycled.

Even when PET is collected, existing processes typically “down-cycle” it into lower-value plastics and fibers that will eventually become waste themselves.

The Edinburgh team tackled the problem from a different angle. They began by breaking PET into terephthalic acid (TPA), one of the two small molecules used to manufacture the polymer.

Bacteria turn plastic Into medicine

Using standard synthetic steps, they next tweaked TPA into a compound that E. coli can import. Finally, they rewired the microbe’s metabolism so that, once the compound is inside, the cell performs a series of chemical moves that ends with paracetamol (also known as acetaminophen).

Each step is already notable, but the most important one is how the transformed bacteria execute a maneuver called the Lossen rearrangement.

In the world of laboratory chemistry this reaction usually needs harsh conditions. Inside the cell, in contrast, it proceeds at room temperature, in water, and without generating meaningful carbon dioxide emissions.

Stephen Wallace, an expert in biotechnology at the University of Edinburgh, is the study’s senior author.

“This work demonstrates that PET plastic isn’t just waste or a material destined to become more plastic,” he said. “It can be transformed by microorganisms into valuable new products, including those with potential for treating disease.”

Nine tablets from a liter bottle

In laboratory flasks, the modified E. coli converted up to 90% of the starting PET-derived compound into paracetamol within 24 hours.

Although the yields are modest on an industrial scale – each one-liter soft-drink bottle would produce roughly nine standard 500 mg tablets. The experiment proves it can be done. It also demonstrates that the process can be dramatically scaled up.

The entire sequence happens in a single “one-pot” fermentation that resembles beer brewing. Because the process requires no extreme heat or pressure, it produces only a fraction of the carbon footprint of petrochemical production.

According to Wallace and colleagues, similar strategies could be applied to convert plastic waste into over-the-counter medicines, specialty polymers, and agricultural chemicals.

Biotech reimagines plastic waste

The achievement is part of a growing movement called engineering biology. It blends genetic engineering, metabolic design, and traditional chemistry to create living “microbial factories.”

The University of Edinburgh hosts one of the largest groups working in the field. The paracetamol project benefited from both government funding and help from the pharmaceutical company AstraZeneca.

Ian Hatch is the Head of Consultancy at Edinburgh Innovations, the university’s commercialization service.

“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,” he said.

“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.”

What’s next for plastic medicine?

Although the engineered cells churn out paracetamol efficiently in the lab, several hurdles remain before the process can compete with conventional factories.

The first is scale. Industrial bioreactors can hold hundreds of thousands of liters. Scientists must demonstrate that the bacteria behave reliably at that scale.

Another challenge is adding an enzyme-based step to break down mixed PET into clean TPA without costly purification.

Regulatory questions also loom. Medicines made by microbes must meet stringent purity standards. Researchers must conduct a full life-cycle analysis to confirm the method is truly greener and cheaper at large scale.

Still, the researchers are optimistic. Similar microbial fermentation facilities already manufacture the diabetes drug insulin and the antimalarial artemisinin precursor at multi-ton volumes.

Plastic finds new purpose

People around the world buy more than a million plastic bottles every minute. Many will end up floating in the ocean or buried in dumps, their useful life measured in minutes but their persistence in centuries.

By showing that a common bacterium can upcycle one a common plastic into a life-saving medicine in under a day, the Edinburgh team has made a powerful point.

Their work provides a striking illustration of what a circular, low-carbon chemical industry might look like.

The research does not, on its own, solve the plastic crisis or secure drug supplies. But it opens a window onto a future where the boundary between “waste” and “resource” is blurred, and where healing the planet could go hand in hand with healing people.

The study is published in the journal Nature Chemistry.

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