Bioremediation of Plastic Pollution

自从合成塑料的发明和随后的一次性塑料的广泛采用，塑料污染问题已经成为地方病。目前，每年有480万至1270万吨塑料进入海洋。这些塑料中的一大部分被称为微塑料，由于它们进入包括人类在内的各个层面的食物链，因此引起了人们的极大关注。最近，在环境中发现了能够降解塑料成分（如聚对苯二甲酸乙二醇酯（PET））的微生物，这种能力已转移到大肠杆菌中。然而，PET酶（PET消化酶）尚未被转移到酵母中。酵母（如酿酒酵母）具有适应恶劣工业规模条件的天然能力，天然分泌具有生物活性的蛋白质，并已广泛用于合成高滴度的重组蛋白。因此，酵母具有作为PETase表达系统在许多工业和环境环境中降解微塑料的潜力。因此，该项目将研究对酿酒葡萄球菌进行基因改造以表达、折叠和分泌PETase。该项目将研究PETase在许多不同菌株背景下的活性，并利用数量性状位点和定向进化来产生最大化PETase活性同时最小化毒性的菌株。这样做的目的是创造一种适合在各种不同环境下降解微塑料中的PET的酵母菌株。

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.