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

据估计，每年有800万吨塑料垃圾最终进入海洋，到2050年，海洋中的塑料重量可能会超过鱼类。这种塑料不仅对海洋生态系统非常危险，而且还会隔离从不可再生化石燃料中提取的材料，目前全球每年只有14%的塑料被回收利用。据估计，回收剩余86%的塑料可产生高达1200亿美元的收入，但必须开发新的方法和工艺，将废塑料转化为增值产品，以实现这一潜力。拟议的研究将侧重于将聚对苯二甲酸乙二醇酯(PET)作为生物“分子向上循环”平台的原料，以生产附加值高、与工业相关的小分子。在英国，PET占塑料垃圾的15%，其中约60%是合成纤维，30%是塑料瓶，其他用途包括塑料包装和薄膜以及用于制造的热成型。虽然化学和热回收PET的方法已经很成熟，但在整个塑料生命周期中，价值都在急剧下降，废弃的PET瓶的价值比原始聚合物低86%。这项奖学金计划结合了化学和生物科学的尖端研究，将废弃的PET转化为高价值的小分子。这项研究将通过以下两个方面解决全球塑料垃圾灾难：(I)减少未来沉积在环境中的塑料垃圾的数量；(Ii)通过新的“分子向上循环”过程，将先前存在的低价值废物产品转化为与工业相关的增值产品。这项研究将分两个阶段进行。最初，将开发一种强大而高效的塑料降解过程。这将利用从垃圾填埋场发现的微生物中分离出来的PET降解酶，这些微生物已经进化到使用PET作为生长的碳源。在第二阶段，PET降解技术将与‘微生物细胞工厂’相结合，我们将对其进行基因编程，将PET的降解产物转化为具有工业意义的小分子。该项目的最初目标将是合成香草醛--香草醛是香草豆的主要萃取物，也是香草兰特有的气味和味道的主要分子。香兰素被广泛用于香料和香料，也是生产精细化学品(如药品)的有价值的中间体。因此，香兰素具有巨大的商业价值，据估计，到2025年，全球香兰素市场将达到7.245亿美元。除此之外，该项目还具有生产一系列其他高价值小分子的巨大潜力，这些小分子可以通过开发和集成新颖的、生物兼容的化学反应与PET降解系统来获得。这类化合物包括药品、香料/调味料化合物、农用化学品和聚合物。因此，预计该项目将具有重要的学术和工业价值，并通过从自然环境中消除塑料垃圾对环境产生积极影响。

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.