🔬 Science · ♻️ Circular Economy · 💊 Biotechnology

Bacteria that recycle plastic into medicines: from PET to paracetamol

Scientists at the University of Edinburgh have demonstrated that genetically modified Escherichia coli bacteria can be integrated into a production route capable of transforming a PET plastic derivative into paracetamol. This breakthrough combines organic chemistry, synthetic biology, and the circular economy, and raises a far-reaching question: can waste from a bottle become a raw material for manufacturing a medicine?

Schematic of the study published in Nature Chemistry : a PET-derived substrate is integrated with a biocompatible Lossen reaction and a metabolic pathway designed to produce paracetamol. Image: Nature Chemistry, open access.

🌍 An environmental problem that needs new answers

Plastic remains one of the planet's greatest environmental challenges. The United Nations Environment Programme estimates that the world generated around 400 million tons of plastic waste in 2024. The sheer scale of this waste stream compels us to think beyond simple disposal: reduce, reuse, recycle, and increasingly, find ways to transform waste into higher-value products.

In this context, the concept of upcycling emerges : instead of recovering a material to manufacture a product of similar value, the aim is to transform it into a substance of greater economic or technological value. The Edinburgh research takes this idea to a particularly striking area: pharmaceuticals .

PET is one of the everyday plastics that can serve as a carbon source for chemical and biological recycling strategies. Illustrative image: Wikimedia Commons, CC BY-SA 4.0 license.

🧬 What did the researchers at the University of Edinburgh do?

The work, led by Professor Stephen Wallace and published in Nature Chemistry , focuses on a reaction known as the Lossen rearrangement . The novelty lies not in having discovered this reaction, which belongs to classical organic chemistry, but in demonstrating that it can function in an environment compatible with living cells and be linked to the metabolism of E. coli .

The researchers engineered bacteria with modified metabolic pathways so that certain intermediates could be converted into molecules of interest. Among these is paracetamol (acetaminophen) , a widely used medication for pain relief and fever reduction.

🧪 From plastic to molecule: the process explained simply

To understand the scope of the discovery, one must follow the transformation chain. A PET bottle does not go directly from its plastic form to a tablet. First, its chemical components need to be accessed.

1. ♻️ PET becomes a chemical raw material

The team used PET from a discarded bottle and transformed it through chemical processes to obtain terephthalic acid . This compound is one of the fundamental monomers of PET and constitutes a suitable starting point for further research.

2. ⚗️ The substrate for the Lossen reaction is constructed

Starting with terephthalic acid, scientists prepared a specific substrate that can undergo the Lossen rearrangement. This step is important because PET is not, by itself, a molecule that the bacteria can directly transform into paracetamol.

3. 🦠 Modified E. coli enters the scene

The bacterium functions as a small biological platform. The team used genetically modified strains of E. coli that allow them to direct the metabolic flow toward the desired products.

4. 🔄 Chemistry and biology work together

The crucial point is the combination of a non-enzymatic chemical reaction with cellular metabolic processes. The study found that phosphate present in cells can catalyze the Lossen rearrangement under conditions compatible with bacterial life.

5. 💊 The intermediary is transformed into paracetamol

Using enzymes incorporated into the metabolic pathway, the researchers directed the intermediates toward 4-aminophenol and ultimately toward paracetamol. Under the optimized conditions described in the scientific article, the paracetamol yield reached 92% from the PET-derived substrate .

⏱️ Is it really possible to produce it in less than 24 hours?

The answer requires significant precision. The University of Edinburgh reported that the conversion via fermentation could be accelerated to produce paracetamol in less than 24 hours , under the experimental conditions used. This figure is one of the reasons why the announcement had such a significant international impact.

However, this should not be interpreted as meaning that a full bottle is transformed into a commercially viable quantity of medication in less than a day. The experiment was conducted using chemical intermediates derived from PET and at a laboratory scale . Implementing this concept in an industrial plant requires addressing raw material preparation, volumetric productivity, product recovery and purification, energy consumption, and waste management.

🌱 Why can it be more sustainable?

Conventional paracetamol manufacturing uses chemical pathways based on raw materials derived from fossil fuels. The appeal of the new approach lies in replacing some of that fossil carbon with carbon already present in plastic waste .

Furthermore, the biological process takes place under relatively mild conditions. The University of Edinburgh highlighted that the fermentation stage occurs at room temperature and that the method produced virtually no carbon emissions in the reported demonstration . The scientific article, for its part, indicates that the next step should include a quantitative life cycle assessment to verify which environmental benefits are maintained when the process is scaled up.

📊 The results that make the study relevant

🧠 An innovation that goes beyond paracetamol

Perhaps the most interesting aspect of the work is not the drug itself, but the technological platform . The authors propose that biocompatible chemistry can expand the range of reactions that cells are capable of performing and allow the conversion of waste products into various industrial molecules.

In other words, the goal would not be to create a single "bacteria that makes paracetamol", but to develop programmable cellular microfactories capable of receiving raw materials from waste and converting them into higher value products.

This logic connects three fields that for a long time evolved along separate paths:

• 🧬 Synthetic biology: modifies microorganisms to perform specific functions.
• ⚗️ Organic chemistry: provides molecular transformations that are not naturally part of metabolism.
• ♻️ Circular economy: seeks to keep materials and carbon within the production system for as long as possible.

⚠️ What are the current limits ?

The discovery is promising, but it is still far from meaning that plastic bottles can be taken to a factory tomorrow and massively converted into paracetamol tablets.

• Industrial scale: results must be transferred from laboratory cultures and reactions to larger volume bioreactors.
• Productivity: it is not enough to obtain a high chemical yield; it also matters how much product is generated per liter and per unit of time.
• Actual raw material: Commercial plastic waste contains mixtures, colorants, additives, and contaminants that can complicate the process.
• Purification: a pharmaceutical active ingredient must meet extremely demanding purity standards.
• Quality control: any medicine intended for patients requires a validated and regulated manufacturing chain.
• Life cycle analysis: the environmental benefit must be verified by considering all stages, from PET preparation to final purification.
• Costs: the technology must compete economically with existing chemical routes.

💊 Is the paracetamol obtained a ready-to-use medication?

No. The study demonstrates the synthesis of the paracetamol molecule through a biotechnological route. This does not equate to producing a finished, packaged, and authorized drug for sale.

In a real pharmaceutical supply chain, there are additional stages: purification, characterization, quality specifications, formulation, stability testing, process validation, microbiological controls, and compliance with applicable regulations. Therefore, this advancement should be understood as a scientific and technological demonstration , not as a new drug available in pharmacies.

Paracetamol tablets. Illustrative image; does not represent the experimental product obtained in the study. Wikimedia Commons, CC BY 2.0 license.

🔬 What exactly does scientific research say?

The article "A biocompatible Lossen rearrangement in Escherichia coli ," published in Nature Chemistry on June 23, 2025, describes the reaction and its integration with E. coli metabolism . The authors show that the substrate can be synthesized from PET and that the pathway can lead to industrial molecules, including paracetamol.

The study also indicates that the reaction occurs under cell-compatible conditions and that phosphate acts as a catalyst. This combination is particularly relevant because it allows for a strategy that does not rely solely on conventional chemistry or natural biosynthesis.

"The real innovation lies not only in manufacturing paracetamol from plastic, but in demonstrating that synthetic chemistry and biology can work together within the same production platform."

🚀 What could come next?

The team itself proposes several lines of development: integrating PET depolymerization more directly with biocatalysis, intensifying the process in bioreactors, improving the metabolic pathway, and conducting life cycle analyses to quantify the environmental benefits.

If these challenges are resolved, the concept could evolve from a laboratory demonstration into a new generation of circular pharmaceutical manufacturing processes : waste as a carbon source, microorganisms as factories, and biocompatible chemistry as a bridge between the two worlds.

🌎 A paradigm shift: from waste to resource

For decades, recycling primarily meant recovering a material for reuse. The Edinburgh research proposes a more ambitious approach: chemically breaking down waste, recovering its carbon, and using it to build entirely different molecules .

This transformation has economic and environmental implications. A bottle that previously ended up in a landfill or could be turned into another plastic object could, in principle, become a raw material for high-value chemical products.

The challenge will be to demonstrate that this transformation also works efficiently, safely, economically competitively, and environmentally beneficially when moving from a few milliliters in the laboratory to industrial facilities.

🧾 Frequently Asked Questions

Do bacteria eat a PET bottle directly?

No. PET is first processed to obtain chemical intermediates. These compounds are then incorporated into the biotransformation pathway.

Does the bacteria directly produce a pill?

No. It produces the paracetamol molecule via an experimental route. Manufacturing a finished drug requires numerous additional steps.

Was the yield really 92%?

Yes, the scientific article reports a final yield of up to 92% paracetamol under optimized conditions using the PET-derived substrate employed in biotransformation.

Could this solve the global plastic problem?

Not on its own. It can become a tool within a much broader strategy that includes reducing consumption, reusing, recycling, materials design, waste management, and new valorization technologies.

When will it arrive on the market?

The study did not establish a commercialization date. Before that, it would be necessary to address scaling, productivity, purification, process economics, environmental analysis, and regulatory requirements.

📝 Conclusion

Converting PET plastic into paracetamol using genetically modified bacteria might seem like something out of science fiction at first glance. However, research published in Nature Chemistry demonstrates that this chemical and biological process is possible on an experimental scale.

What is truly significant is the convergence of two contemporary problems: plastic pollution and dependence on fossil raw materials to manufacture chemicals . Instead of viewing waste as the end of a chain, biotechnology attempts to transform it into the beginning of another.

The path to a circular pharmacy has only just begun. But the idea has already been put forward: a discarded bottle can contain carbon that, with the right chemistry and biology, can re-enter the economy as a high-value molecule.