21ENGBIO: Engineering novel amyloid biofilm based material for capture and degradation of micro-plastics

塑料污染，即塑料物体和颗粒的积累，在英国和世界范围内都是一个当前、紧迫和代价高昂的环境问题。聚对苯二甲酸乙二醇酯(PET)是聚酯的化学名称，聚酯是一种常见的塑料，它本身需要800年的时间才能降解。宠物粪便也倾向于通过磨损转化为微塑料，众所周知，这会对动植物产生不利影响。最近，研究人员发现了一种名为PETase的酶，它可以主动将PET降解成无害的物质。目前，PETase在塑料降解中的应用受到溶液中PETase的使用要求的限制。我们建议将PETase与由淀粉样蛋白纤维形成的网状生物材料相结合，以形成一种新的材料。这种材料可以通过生物工程细胞出口，生成具有延展性的无毒网状物，可能用于大规模设计以去除和降解塑料垃圾。淀粉样纤维是一种具有特征形状的蛋白质结构。已知一些淀粉样纤维与阿尔茨海默病、帕金森氏病和系统性淀粉样变性等疾病有关。然而，许多淀粉样蛋白的形成是有益的，或者说是“功能”的，因为它们发挥了基本的生物学作用。人们已经发现，像大肠杆菌这样的细菌会利用由卷曲蛋白制成的淀粉样纤维来形成一层保护性的生物膜，因为淀粉样纤维形成了一层难以穿透的网状结构，保护大肠杆菌免受病毒感染。要做到这一点，大肠杆菌细胞自然包含一个系统，该系统通过将单个卷曲蛋白推出细胞时将单个卷曲蛋白粘合在一起，以受控的方式迫使淀粉样纤维在细胞外形成。已经有可能劫持这个系统来出口由不同的淀粉样蛋白制成的淀粉样纤维，例如来自酵母的另一种功能性淀粉样蛋白Sup35。Sup35在酵母细胞中形成淀粉样纤维，然后通常被用作其他酵母细胞的信使。重要的是，Sup35有三个部分，其中只有两个是形成淀粉样蛋白纤维所必需的，这两个部分被称为Sup35 NM。我们打算用PETase等酶来取代第三部分，使Sup35 NM淀粉样纤维具有降解PET的功能。在这个项目中，我们打算通过生物工程使大肠杆菌细胞产生并输出一种含有PETase和其他塑料降解酶修饰的Sup35 NM淀粉样纤维的新材料的生物膜。这将产生一种坚固但可延展的无毒物质，可以应用于过滤器等设备，甚至可以打印到具有降解塑料能力的复杂设计上。由于塑料和淀粉样蛋白都不能很好地与水相互作用，淀粉样蛋白网状物很可能能够捕获并改善塑料降解酶和塑料颗粒之间的接触。此外，在淀粉样蛋白网状物中可以获得非常高密度的酶将进一步改善塑料降解，并且结合不同类型的酶的能力可能会提高总的塑料降解活性。因此，提出的淀粉样网可以为塑料污染问题提供一种环境解决方案。

Plastic pollution, whereby plastic objects and particles are accumulated is a current, pressing, and costly environmental problem both in the UK and worldwide. Polyethylene terephthalate (PET) is the chemical name for polyester, a common type of plastic which would take up to 800 years to degrade on its own. PET waste also tends to be converted by abrasion into microplastics, which are known to have adverse effects on animals and plants. Recently, researchers have discovered an enzyme called PETase which can actively degrade PET into non-harmful substances. Currently, the application of PETases to plastic degradation is limited by the requirement to deploy PETases in solution. We propose combining PETases with a meshed biomaterial formed from amyloid fibrils to form a novel material. This material can be exported via bioengineered cells to generate a non-toxic mesh with malleable properties for potential use in large scale designs to remove and to degrade plastic waste.Amyloid fibrils are a type of protein structures with a characteristic shape. Some amyloid fibrils are known to be associated with diseases such as Alzheimer's disease, Parkinson's disease, and systemic amyloidosis. However, many amyloid forming are beneficial, or "functional" in that they fill essential biological roles. Bacteria such as E. coli have been found to utilise amyloid fibrils made from the curli protein to form a protective biofilm as the amyloid fibrils form a hard to pass through mesh which protects the E. coli against viral infection. To do this, the E. coli cells naturally contain a system which forces the amyloid fibrils to form outside the cells in a controlled manner by sticking individual curli proteins together as they are pushed out of the cell. It is already possible to hijack this system to export amyloid fibrils made from different amyloidogenic proteins, for example another functional amyloid protein from yeast called Sup35.Sup35 forms amyloid fibrils in yeast cells and normally is then used as a messenger to other yeast cells. Importantly, Sup35 has three parts and only two of these are required to make the amyloid fibrils, these two parts are known as Sup35NM. We intend to replace the 3rd part with enzymes such as PETase which could functionalise the Sup35NM amyloid fibrils and imbue them with PET degrading functionality.In this project, we intend to bioengineer E. coli cells to generate and export a biofilm containing the novel material of Sup35NM amyloid fibrils decorated with PETase and other plastics degrading enzymes. This will generate a robust yet malleable, non-toxic substance which could be applied to devices such as filters or even 3D printed onto complex designs with the ability to degrade plastics. Since neither plastics nor amyloid interact well with water, the amyloid mesh will likely be able to capture and to improve the contact between the plastic degrading enzymes and the plastic particles. Furthermore, the very high density of enzymes that can be achieved in an amyloid mesh will further improve plastic degradation, and the ability to combine different types of enzymes may improve the total plastic degradation activity. The proposed amyloid mesh, therefore, could offer an environmental solution to the problem of plastic pollution.