Dr Neil Dixon, reader at The University of Manchester, discusses the potential for bacteria to play a central role in creating a wide-scale circular economy.
PET plastic has long been a concern due to the sheer volume that is created globally, and the comparatively small volume that is recycled and reused. But it continues to play an important role in our modern world, and that isn’t going to change overnight – the use of plastics is expected to triple by 2060, according to the Organisation for Economic Co-operation and Development (OECD).
That’s why we need to focus on more sustainable plastic usage by creating a circular economy. Often plastic packaging is used only once, due to cost and quality concerns. Despite a rise in home and industrial recycling efforts, there is still a systemic problem which means our infrastructure is unable to process the vast amount of material collected.
This presents a challenge to find an effective solution. However, the scientific community has risen to this challenge, and we’ve seen great strides in a range of areas.
One key area of progress has been developing microbial degradation of plastics. Bacteria, which have been shown to degrade and assimilate certain types of plastic, have been a key area of international research since 2016, and at The University of Manchester, my colleagues and I have made a biotechnological breakthrough that we hope will enable us to introduce bacterial plastic degradation on a wider scale.
The plastic challenge and finding a solution
Part of the reason plastic is difficult to break down is its chemical structure. It is made up of monomers – small molecules which are bonded together to form polymers. However, there have been examples of enzymes and bacteria that have been able to both degrade plastic down into the constituent monomers and assimilate and grow on the released monomers.
How this has happened is unclear. Generally, bacteria have adapted to consume substances available in the natural world over thousands of years of evolution, but in the case of plastic, we have seen bacteria very rapidly become adept at breaking down and consuming these plastics. We can only assume that there has previously been something natural with a similar make-up that has given the bacteria a head-start.
At the Manchester Institute of Biotechnology, we’ve been working hard to understand the “how” and identify the mechanisms behind this activity. For example, how the bacteria recognise and uptake the monomers into their cells.
We’ve studied the key proteins within the bacteria cells that are involved in transporting the PET breakdown product, terephthalate (TPA), inside bacteria.
We have identified the solute binding protein TphC as key to the uptake of TPA. By studying TphC, we can more closely analyse its protein structure and its ability to recognise TPA. This is a significant breakthrough as it offers the potential to utilise the power of bacteria on a much larger scale.
A long-term solution to plastic
Understanding, at a molecular level, how these molecules are imported into bacteria cells, and which genes control this, means that we can genetically engineer bacteria to make them as effective as possible at breaking down plastic materials. We can accelerate the evolution of plastic-eating bacteria even further by quickly creating several bacteria that are extremely effective at breaking down plastic.
Through genetic engineering we can also make them more resilient to different environments, such as saline solutions, to minimise any indirect environmental impact.
Although it is only early days, this development has a huge amount of promise and the team at the Manchester Institute of Biotechnology has ambitious plans to scale up our work.
Alongside more effective methods of collection, we believe microbial degradation has the potential to play a significant role in reducing plastic pollution, providing end–of–life solutions for plastic and creating a circular economy on a large scale.
