Molecular up-cycling: bio-transforming waste plastic into value-added products

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It is estimated that 8 million tonnes of plastic waste end up in the oceans each year and that by 2050 there could be more plastic in the seas by weight than fish. This plastic is both incredibly dangerous to marine ecosystems and also sequesters materials prepared from non-renewable fossil fuels, with just ~14% currently being recycled globally each year. It has been estimated that recycling the remaining 86% of plastics could generate up to $120bn, but new methods and processes to transform waste plastic into value-added products must be developed in order to realise this potential. The proposed research will focus on polyethylene terephthalate (PET) as a feedstock for a bio-based 'molecular up-cycling' platform to produce value-added, industrially relevant small molecules. PET accounts for 15% of plastic waste in the UK, out of which ~60% is accounted for by synthetic fibres and 30% by plastic bottles, whilst other uses include plastic wrappers and films and thermoforming for manufacturing. Although chemical and thermal methods for PET recycling are well-established, there is a dramatic loss in value throughout the plastic life-cycle, with the value of the waste PET bottles being 86% lower than the virgin polymer.This Fellowship proposal unites cutting edge research from both the chemical and biological sciences to transform waste PET into high-value small molecules. The research will address the global plastic waste disaster twofold by (i) decreasing the amount of plastic waste deposited in the environment in the future and (ii) transforming pre-existing, low-value waste products into industrially relevant, value-added products via a new 'molecular up-cycling' process. The research will be organised into two phases. Initially, a robust and efficient plastic degradation process will be developed. This will exploit PET degrading enzymes that have been isolated from microbes found in landfill sites, which have evolved to use PET as a carbon source for growth. In the second phase, the PET degradation technology will be integrated with 'microbial cell factories', which we will genetically programme to turn the degradation products of PET into industrially relevant small molecules. The initial target of the project will be the synthesis of vanillin - the primary extract from the vanilla bean and the primary molecule responsible for the characteristic smell and taste of vanilla. Vanillin is used extensively for flavours and fragrances and is also a valuable intermediate in the production of fine chemicals such as pharmaceuticals. As such, it has huge commercial value, with the global market for vanillin estimated to reach $724.5 million by 2025. Beyond this, the project also holds great potential for the production of a range of other high-value small molecules which are accessible through developing and integrating novel, bio-compatible chemical reactions with the PET degradation system. Such compounds include pharmaceuticals, fragrance/flavouring compounds, agrochemicals and polymers. As such, it is anticipated that this project will have significant academic and industrial value, as well having a positive impact on the environment by removing plastic waste from the natural environment.