Researchers use bacteria to convert plastic waste into human therapeutics, including insulin

A new study from the Manchester Institute of Biotechnology describes a novel biological method to convert mixed municipal waste-like fractions – including food scraps, plastics, and textiles – into valuable bio-products. This new approach could significantly reduce waste sent to landfills and cut greenhouse gas emissions. 

Led by Dr Neil Dixon, the team utilised the bacterium Pseudomonas putida, renowned for its resilience and adaptability, to process complex waste streams into bioplastics and even therapeutic proteins. This research offers a promising pathway toward achieving a circular economy, where waste is reused and repurposed rather than discarded. 

Turning waste into wealth 

Every year, over two billion tonnes of municipal solid waste (MSW) is generated worldwide. This figure is expected to rise to 3.4 billion tonnes by 2050. Conventional waste treatments like incineration and landfill contribute to environmental pollution and greenhouse gas emissions, but the Manchester team’s approach addresses these issues by creating a circular bioprocess whereby anthropogenic waste is turned into useful products. 

Firstly, the team pre-treated representative waste types via enzymatic hydrolysis, a process that breaks down the waste into monomers. These monomers were then added to a bioreactor containing and engineered strain of Pseudomonas putida, which used them for metabolic activity and bioproduction. 
 

Tackling environmental pollution 

The process offers a way to mitigate the impact of anthropogenic waste on the environment. A life cycle assessment revealed that the proposed approach could reduce the carbon footprint of waste management by up to 62% compared to traditional methods like landfill or incineration. The study also found that this new process could be more cost-effective, with savings of up to 37% compared to current waste treatments. 

Key to this success is the adaptability of Pseudomonas putida. Unlike most microorganisms, which struggle to process multiple types of waste simultaneously, the engineered bacteria can metabolise a mix of sugars, acids, and oils derived from various waste materials. 

“This flexibility makes our system robust and reliable, regardless of the type of waste input,” says Dr Dixon. 

 Real-world applications 

To demonstrate the potential of this technology, the team focused on two products: 

1. Bioplastics: the bacteria produced polyhydroxyalkanoates (PHAs), a biodegradable alternative to petroleum-based plastics. These bioplastics are already used in applications ranging from food packaging to medical implants. 
2. Therapeutic proteins: the engineered bacteria successfully produced human insulin analogues used for treating diabetes, human interferon-alpha2a, a protein used in treatments for viral infections and some cancers, and a synthetic HEL4 nanobody. 

These dual outputs highlight the versatility of the system, which could cater to both high-volume products like bioplastics and high-value applications such as pharmaceuticals. 

Towards a circular economy 

This project aligns with global efforts to transition to a circular economy, where resources are reused and waste is minimised. By leveraging waste as a resource, the Manchester team’s method addresses both environmental and economic challenges. 

“This work illustrates how science can tackle real-world problems,” notes Dr Dixon. “With further development, this technological concept could be integrated into municipal waste management systems, turning waste into a valuable resource.”

Looking ahead 

While the study is still in its proof-of-concept stage, the potential applications are vast. Future work will focus on scaling up the process, refining enzyme systems for even greater efficiency, and exploring additional waste inputs such as rubber and nylon. 

As cities and nations grapple with growing waste volumes, this research offers a sustainable, scalable solution that not only addresses waste management but also contributes to climate change mitigation.