Breaking the Wall of Plastic-to-Medicine Conversion

Breaking the Wall of Plastic-to-Medicine Conversion

Global Call 2026 Finalist Interview: Engineering & Technology

Stephen Wallace is Professor of Chemical Biotechnology and a UKRI Future Leaders Fellow at the University of Edinburgh, UK. His research reprogrammes microorganisms to transform waste and renewable feedstocks into medicines, chemicals and materials, advancing a more sustainable future for manufacturing. His work bridges chemistry and biology to develop new approaches that replace fossil-derived production with circular, low-carbon alternatives.

Which wall does your research or project break?  

For more than a century, pharmaceutical manufacturing has depended on fossil carbon. At the same time, billions of kilograms of plastic waste are discarded every year, creating one of the world's most pressing environmental challenges. Although both problems stem from our reliance on the same carbon resources, they have always been treated as separate.

Our research breaks the wall between plastic waste and essential medicines by showing, for the first time, that discarded plastic can become the starting point for pharmaceutical manufacturing. Rather than viewing plastic as waste to be disposed of, we treat it as a valuable carbon resource that engineered microbes can transform into medicines such as paracetamol and levodopa, a frontline treatment for Parkinson's disease.

This challenges one of the fundamental assumptions of modern manufacturing: that high-value medicines must be produced from newly extracted fossil resources. Instead, we demonstrate a circular alternative in which waste carbon is continually repurposed into products that benefit human health.

Beyond addressing plastic pollution, this work offers a new vision for sustainable manufacturing. By combining engineering biology with new-to-nature chemistry, we establish a platform that could ultimately enable many chemicals and medicines to be produced from waste rather than fossil feedstocks. In doing so, we hope to accelerate the transition towards a circular economy where environmental sustainability and human health are no longer competing priorities, but are advanced together through scientific innovation.


What is the main goal of your research or project?

Our goal is to redefine how society manufactures medicines by replacing the linear, fossil-based model of pharmaceutical production with a circular system built on engineering biology. We believe waste should no longer be viewed as something to dispose of, but as a valuable carbon resource that can be transformed into products that benefit human health.

To achieve this, we are developing microbial technologies that convert discarded plastics into essential medicines through the integration of engineered metabolism with new-to-nature chemistry. Our demonstration of plastic-to-medicine conversion is the first step towards a much broader vision: enabling waste carbon to become a sustainable feedstock for pharmaceutical manufacturing.

Ultimately, we aim to establish a new manufacturing platform that is independent of virgin fossil resources, produces lower greenhouse gas emissions, and contributes to a circular economy in which carbon remains in productive use for longer. While our initial work focuses on medicines such as paracetamol and levodopa, the underlying technologies have the potential to extend far beyond these examples to many other pharmaceuticals and high-value chemicals.

More broadly, our ambition is to help reshape the relationship between environmental sustainability and healthcare. Rather than viewing these as competing priorities, we aim to demonstrate that engineering biology can address both simultaneously – transforming one of humanity's greatest environmental challenges into a resource that improves human health.


What impact does your research or project have on society?

Our research demonstrates that solving environmental challenges can also create new opportunities to improve human health. By showing that plastic waste can be transformed into essential medicines, we challenge the assumption that sustainability and healthcare must be addressed separately. Instead, we demonstrate that a single technological innovation can contribute to both. In the near term, our work provides a new route towards reducing reliance on virgin fossil resources in pharmaceutical manufacturing while creating value from materials that would otherwise be discarded. This has the potential to reduce greenhouse gas emissions, promote more circular use of carbon, and encourage new approaches to managing plastic waste. The broader impact, however, lies in changing how we think about waste itself. Rather than seeing discarded plastics as an environmental liability, our research reimagines them as a valuable resource for producing medicines and other high-value products. We hope this shift in perspective will inspire new technologies that keep carbon in productive use for longer, helping to build a more sustainable manufacturing economy. Perhaps most importantly, our work demonstrates the power of engineering biology to address multiple global challenges simultaneously. As the world seeks solutions to climate change, resource scarcity, and growing healthcare demands, we believe biology can become a transformative manufacturing technology for the twenty-first century. Our ambition is not simply to recycle plastic, but to redefine the relationship between waste, sustainability, and human health, creating a future where environmental stewardship and medical innovation advance together.

What advice would you give to young scientists or students interested in pursuing a career in research, or to your younger self starting in science?

My advice would be to stay curious and not be afraid to work on problems that seem too difficult or too unconventional. Many of the most exciting discoveries happen at the boundaries between disciplines, where there are no established roadmaps and no guarantee that an idea will work. That uncertainty can feel uncomfortable, but it is also where real breakthroughs begin.

Early in my career, I sometimes worried about not fitting neatly into a single scientific discipline. Looking back, I now see that as one of my greatest strengths. Some of our most important discoveries have come from bringing together chemistry, biology, engineering, and sustainability in ways that had not been attempted before. Innovation rarely happens by staying within traditional boundaries.

I would also encourage young scientists to choose problems that genuinely matter to them, rather than simply following fashionable research areas. Scientific careers are long, and the biggest challenges often require years of persistence, resilience, and creativity. It is much easier to sustain that effort when you are motivated by the question itself rather than by the next publication or grant.

Finally, remember that science is a profoundly optimistic endeavour. Every experiment, whether it succeeds or fails, teaches us something new about the world. If we are willing to remain curious, embrace collaboration, and think boldly, research gives us the opportunity not only to understand the world, but also to improve it.


What inspired you to be in the profession you are today?

I've always enjoyed asking "what if?" Science gave me a career where curiosity isn't just encouraged—it's the starting point for discovering solutions that can have a real impact on the world.
 

What is one surprising fact about your research or project that people might not know?

The key chemistry behind our plastic-to-paracetamol technology was discovered completely by accident... We were trying to achieve something entirely different when an unexpected reaction revealed a new way of making medicines from plastic waste.

What’s the most exciting moment you've experienced over the course of your research or project?

Seeing the first analytical data confirming that a piece of plastic had become a medicine was surreal. Years of ideas, failed experiments, and optimism suddenly became a reality!