Assessing the environmental biodegradation of next-generation polyolefin plastics

Plastics have become global pollutants and have been detected in every environment in the planet. They have an impact on flora and fauna and also contribute to the spread of pathogens and antibiotic resistance genes. To prevent the harmful accumulation of plastics, initiatives such as the UK Plastics Pact aim at having a 100% of plastic packaging fully compostable and recyclable by 2025.

This has led to the development of novel plastics with increased biodegradability once they reach the end of their shelf life which could enable their entry in a circular economy.

In this project we will investigate the ability of soil microbial communities to biodegrade next-generation polyolefin plastics. Polyolefin polymers (e.g. polyethylene and polypropylene) are widely used as single-use plastic products especially in the form of films (e.g. plastic bags) and fibres (e.g. face masks). They have low collection and recycling rates, and accumulate in the environment where their degradation is extremely slow, as they require abiotic processes before they can be assimilated via poorly understood processes.

The industrial sponsor in this CASE studentship is Polymateria, a SME specialising in the production of biodegradable polyolefins through a patented biotransformation technology. In this project we will leverage Polymateria's expertise in polymer synthesis and characterisation to evaluate the biodegradation potential of different sustainable and engineered polyethylene and polypropylene materials as well as their impact on the soil

microbiota. We will then seek to understand the pathways and intermediates of polyolefin biodegradation resulting from various environmental and processing conditions. The specific questions we want to address are the following:

1) What formulations of polyethylene and polypropylene can be biodegraded? Polymateria will incorporate a range of polymer additives and blends widely used in the plastic industry.

These plastics will be pre-treated through the exposure to simulated weathering conditions and extensive recycling. Materials will be incubated with soil communities and the resulting polymers and waxes will be studied at the company to characterise their degradation (by GPC and FTIR among other analytical methods).

2) What is the impact of biodegradable plastics on the microbiota of soil? Microbial communities will be incubated with plastics mimicking different environmental conditions. We will assess microbial growth and population dynamics via culturing, DNA isolation and sequencing of 16S rDNA (for bacteria) and ITS (for fungi).

3) What are the organisms and pathways responsible for the biodegradation? We will investigate degradation products using mass spectrometry and NMR, which will allow to identify relevant metabolites derived from plastic. Organisms enriched during plastic degradation will be isolated, sequenced and further characterised in order to identify relevant activities against polyolefins