Bioremediation of Plastic Pollution

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Since the invention of synthetic plastics and subsequent wide spread adoption of single use plastics, the problem of plastic pollution has become endemic. Currently, 4.8 - 12.7 million tonnes of plastic enter the oceans every year. A large subset of these plastics called microplastics are of great concern due to making their way into the food chain at all levels including humans. Recently microorganisms capable of degrading plastic components such as Polyethylene terephthalate (PET) have been identified in the environment and this capability has since be transferred to Escherichia coli. However, PETase (PET digesting enzyme) has yet to be transferred into yeast. Yeast such as S. cerevisiae has a natural ability to harsh industrial-scale conditions, naturally secretes biologically active proteins, and has been widely used for the synthesis of recombinant proteins with high titres. As such yeast holds the potential to be used as a PETase expression system to degrade microplastics in a number of industrial and environmental settings. This project will therefore look into genetically modifying S. cerevisiae to express, fold and secrete PETase. The project will investigate the activity of PETase in many different strain backgrounds and using quantitative trait loci and directed evolution to generate strains that maximise PETase activity while minimising toxicity. This will be done with the aim to create a strain of yeast suitable for the degradation of PET in microplastics in a variety of different settings.