Engineered E. Coli Converts Plastic Bottle Waste into Parkinson's Drug in Bioengineering First
University of Edinburgh researchers engineered bacteria to transform PET plastic into levodopa, a frontline Parkinson's medication, achieving 84 percent conversion from industrial waste in a proof-of-concept published in Nature Sustainability.
Overview
Researchers at the University of Edinburgh have engineered Escherichia coli bacteria to convert polyethylene terephthalate (PET) plastic waste into levodopa (L-DOPA), the primary medication used to treat Parkinson’s disease. The work, published in Nature Sustainability on March 16, represents what the team describes as the first use of engineering biology to transform plastic waste into a therapeutic compound for neurological disease.
The process achieved an 84 percent conversion rate from industrial PET waste, yielding 5.0 grams per liter of levodopa. From a single post-consumer plastic bottle, the researchers isolated enough medication to produce more than 100 clinical doses typically prescribed for early-onset Parkinson’s disease, according to the University of Edinburgh.
What We Know
The approach hinges on a four-step biosynthetic pathway assembled from seven genes drawn from multiple bacterial species. PET waste is first chemically broken down into terephthalic acid (TPA), a monomer building block. The engineered bacteria then convert TPA into L-DOPA through a sequence of enzymatic reactions: Comamonas sp. enzymes handle the initial conversion to protocatechuate, Klebsiella pneumoniae co-factors drive decarboxylation to catechol, and Fusobacterium nucleatum enzymes catalyze the final synthesis steps, as described in the study.
Two key technical obstacles had to be addressed. First, getting TPA into the bacterial cell required expressing a heterologous transporter protein, TpaK, borrowed from Rhodococcus jostii. Second, an intermediate compound, protocatechuate, inhibited downstream enzymes through feedback. The team solved this by splitting the pathway across two cooperative E. coli strains, each handling a different portion of the conversion, as Phys.org reported.
The researchers tested three different PET waste sources: a post-consumer plastic bottle found discarded in Edinburgh, industrial hot-stamping foils from a manufacturing partner, and enzymatically depolymerized PET packaging film. All three yielded levodopa, though the post-consumer bottle produced lower conversions, which the team attributed to residual plasticizers in lower-grade consumer plastic, according to Phys.org.
The team also integrated the microalga Chlamydomonas reinhardtii into the process to capture carbon dioxide emissions generated during catechol production, reducing CO2 levels to undetectable concentrations within 12 hours.
“Plastic waste is often seen as an environmental problem, but it also represents a vast, untapped source of carbon,” said Professor Stephen Wallace, who led the research at Edinburgh’s School of Biological Sciences, in a statement shared by the University of Edinburgh.
What We Don’t Know
The work remains a proof-of-concept, and significant hurdles stand between the laboratory and any pharmaceutical supply chain. “I think the main hurdle that we face right now is scalability,” Wallace told Phys.org. The current process relies on antibiotic selection markers to maintain the engineered pathways, which would need to be replaced with genomic integration for any industrial application.
The post-consumer bottle conversion rate of 49 percent trails the 84 percent achieved with industrial waste, raising questions about how effectively the system can handle the variability of real-world recycling streams. Contaminant removal and direct precipitation of pharmaceutical-grade L-DOPA at scale have not yet been demonstrated.
It is also unclear how the economics compare to existing levodopa manufacturing, which uses well-established chemical synthesis routes. Approximately 50 million tonnes of PET plastic are produced annually worldwide, according to Interesting Engineering, but whether bio-upcycling can compete on cost with conventional production at scale remains an open question.
Analysis
The Edinburgh research sits at an emerging intersection of metabolic engineering and circular economy thinking. Rather than treating plastic waste as material to be downcycled into lower-value products, the team demonstrated that engineered microorganisms can redirect waste carbon into high-value pharmaceutical compounds.
The broader significance may lie less in levodopa itself and more in the platform approach. Professor Charlotte Deane, Executive Chair of UKRI’s Engineering and Physical Sciences Research Council, noted that the research demonstrates how “carbon that would otherwise be lost to landfill or pollution can be turned into high-value products,” as reported by Interesting Engineering. The team has indicated that the same metabolic engineering principles could be applied to produce flavorings, fragrances, cosmetics, and industrial chemicals from plastic waste.
The research was funded by UK Research and Innovation (UKRI), the Engineering and Physical Sciences Research Council (EPSRC), and the Industrial Biotechnology Innovation Centre (IBioIC). The University of Edinburgh has also secured 14 million pounds for the Carbon-Loop Sustainable Biomanufacturing Hub (C-Loop), which will pursue further development of bio-upcycling technologies, according to the University of Edinburgh.
“If we can create medicines for neurological disease from a waste plastic bottle, it’s exciting to imagine what else this technology could achieve,” Wallace said, as quoted by Phys.org.