Engineered bacteria can turn plastic bottles into a Parkinson's drug

Fifty million tonnes of PET plastic are produced every year. Most of it ends up in landfills, incinerators, or the ocean. Meanwhile, L-DOPA - the primary medication for managing Parkinson's disease symptoms - is manufactured using petrochemical feedstocks derived from oil and gas.

A team at the University of Edinburgh has connected these two facts in a way nobody had attempted before. They engineered E. coli bacteria to convert the chemical building blocks of waste PET plastic bottles into L-DOPA. It is the first time a biological process has been used to transform plastic waste into a therapeutic for a neurological disease.

From bottle to building block to drug

The process works in two stages. First, PET plastic - the lightweight, strong material used in most food and drink packaging - is broken down into its chemical components, including terephthalic acid. This step uses established depolymerization methods.

The second stage is where the biology comes in. The engineered E. coli take up terephthalic acid molecules and run them through a series of enzymatic reactions, converting the plastic-derived chemical into L-DOPA (levodopa), the amino acid precursor to dopamine that has been the frontline treatment for Parkinson's disease for over fifty years.

The team, led by Professor Stephen Wallace of Edinburgh's School of Biological Sciences, has demonstrated production and isolation of L-DOPA at preparative scale - meaning enough to characterize and verify, though not yet at industrial volumes.

Why this matters for sustainability

Current recycling processes for PET are incomplete. Mechanical recycling degrades the polymer with each cycle, producing lower-quality material. Chemical recycling exists but is energy-intensive and often economically marginal. Most PET ends up as waste despite being technically recyclable.

The Edinburgh approach reframes PET waste not as a disposal problem but as a carbon source. The valuable carbon atoms locked in discarded plastic bottles become the molecular backbone of a pharmaceutical product. Instead of burning that carbon or burying it, bacteria rebuild it into something with direct medical value.

Traditional pharmaceutical manufacturing relies on finite petrochemical feedstocks. If plastic-to-drug conversion can be scaled, it would create a production pathway that simultaneously addresses plastic pollution and reduces the pharmaceutical industry's dependence on fossil fuels.

The wider bio-upcycling vision

L-DOPA is the proof of concept, but the researchers see it as the opening move in a broader strategy. The same biological engineering approach could potentially produce flavorings, fragrances, cosmetics ingredients, and industrial chemicals from plastic waste. Wallace described the work as just the beginning, noting that if bacteria can create medicines from waste plastic bottles, the range of possible products is large.

The research was carried out at the Carbon-Loop Sustainable Biomanufacturing Hub (C-Loop), a 14-million-pound facility supported by the Engineering and Physical Sciences Research Council (EPSRC) that aims to transform UK manufacturing by converting industrial waste into valuable chemicals and materials.

From lab to factory - the hard part

Demonstrating a biological conversion at lab scale and running it at industrial scale are separated by years of engineering work. The team's next steps involve optimizing the process, improving scalability, and assessing environmental and economic performance more rigorously.

Key questions remain unanswered. What is the yield per kilogram of PET input? How does the cost compare to conventional L-DOPA synthesis? Can the engineered bacteria maintain consistent production over long fermentation runs? What are the purity standards for pharmaceutically active L-DOPA produced this way, and can they meet regulatory requirements?

The process also depends on a reliable supply of depolymerized PET feedstock, which requires its own infrastructure and economics to work at scale.

Liz Fletcher, director of impact and deputy CEO at the Industrial Biotechnology Innovation Centre (IBioIC), which co-funded the research, framed it as proof that sustainable, high-value applications of biology are both practical and effective. The research is also supported by Edinburgh Innovations, the university's commercialization service.

An elegant connection

There is something satisfying about the logic: a material that has become one of the world's most persistent environmental pollutants being converted by engineered microorganisms into a medicine that treats one of the world's most common neurodegenerative diseases. Whether that elegance survives the journey from lab bench to production line is the question that will define this technology's impact.