Bug-Busting Spandex: Biodegrading Textile Blends for Molecular Recycling

废弃纺织品是世界范围内的一个主要问题，最近的报告强调，英国人每年扔掉约3公斤纺织品。虽然一些废弃衣服（约10%）被转售或出口，但近50%的废弃衣服最终被填埋在英国，这是一个错失的回收机会。2020年，全球聚酯纤维市场规模为740亿美元，预计到2027年将增至1240亿美元。聚酯纤维由加工过的聚对苯二甲酸乙二醇酯（PET）制成，包括原始纤维和最近回收的PET。氨纶，也称为莱卡或弹性纤维，是一种重要的弹性纤维，产量为100万吨/年。它被用于许多有弹性的织物中，如运动服，作为与聚酯（如氨纶：聚酯比，15:85或更低）的纺织品混纺。由于结构复杂，这种混纺纺织品的回收利用尤其具有挑战性，然而生物技术方法有可能将聚合物降解成碎片或小分子，用于回收或升级为其他聚合物或材料。该项目旨在确定和开发用于分解聚酯/氨纶织物混合物的酶，并将小分子单体回收到新的聚合物中，作为生物聚合物合成的原料或作为药物前体。这种针对氨纶纤维混纺的“灭虫”策略将为解决主要的纺织废物流问题提供途径。氨纶的一个特别的挑战是它们与其他纺织品混合成织物，而氨基甲酸酯键在温和的条件下很难水解。虽然最近在产生分解塑料PET瓶的生产酶方面取得了重大进展，但在纺织品中分解PET聚酯方面的工作却很少。目前也很少有酶能够切割氨基甲酸酯键。提出了几种获得涤纶/氨纶共混物高产降解酶的策略。对于酶发现和筛选的快速成功至关重要的是合适的分析方法，为此，我们将合成底物，用于在自动化平台上开发显色高通量分析方法，并用于随后在分析HPLC机器上进行筛选。聚酯的生物降解将使用现有的内部petase和酯酶，以及可用的petase进行研究，同时使用机械酶反应条件和离子液体来增强纺织品/酶的相互作用。然后将通过鉴定可以分解氨基甲酸酯键的酶来探索氨纶的生物降解。这将通过两年前在热箱中建立的微生物群落/细菌富集实验的发展，分析，DNA测序和酶鉴定。此外，信息学方法和数据库的使用，以及宏基因组策略，包括我们的宏基因组数据库。然后使用酶诱变方法和高通量自动筛选平台将聚酯和氨纶降解酶结合并优化。使用最佳的酶组合，将测试分离关键芳香酸和胺片段的程序，而剩余的软段成分可能用作生物塑料生产的碳原料。还将探索利用室内氧化酶来提高胺片段价值的途径。在整个项目中，通过与伦敦大学学院塑料废物创新中心的联系，我们将评估所开发技术的社会、经济和环境影响，并收集数据进行生命周期分析。

Waste textiles are a major issue worldwide and recent reports have highlighted that Britons throw away ~ 3 kg textiles each year. While some waste clothing (~10%) is resold or exported, nearly 50% ends up in landfill in the UK which is a missed recycling opportunity. The global polyester fibre market was $74 billion in 2020 and is projected to rise to $124 billion by 2027. Polyester fibre is made from processed polyethylene terephthalate (PET), including virgin fibres, and more recently recycled PET. Spandex, also known as Lycra or Elastane, is an important elastane fibre with production levels of 1 million tonnes/year. It is used in many stretchy fabrics such as activewear as a textile blend with polyesters (e.g. ratio Spandex:PET, 15:85 or less). Such blended textiles are particularly challenging to recycle into useful materials due to the complex structure, however biotechnological approaches have the potential to degrade the polymers into fragments or small molecules for recycling or upgrading into other polymers or materials. This project aims to identify and develop enzymes for the breakdown of polyester/Spandex fabric blends and to recycle the small molecule monomers into either new polymers, for use as a feedstock for biopolymer synthesis, or as a drug precursor. This 'bug-busting' strategy for Spandex textile blends will provide routes to tackle a major problematic textile waste stream. A particular challenge of Spandex is their combination with other textiles into fabric blends, and the carbamate bonds which are hard to hydrolyse under mild conditions. While there have been significant developments recently in generating productive enzymes to break down plastic PET bottles, there has been little work carried on the breakdown of PET polyesters in textiles. There are also currently very few enzymes that cleave the carbamate bond that have been characterized.Several strategies to obtain productive degrading enzymes for polyester/Spandex blends are proposed. Crucial to the rapid success of enzyme discovery and screening will be suitable assays and for this we will synthesise substrates for the development of chromogenic high throughput assays on an automated platform and for subsequent screening on an analytical HPLC machine. The biodegradation of polyesters will be investigated using current in-house PETases and esterases, and available PETases, together with the use of mechanoenzymatic reaction conditions and ionic liquids to enhance textile/enzyme interactions. Then the Spandex biodegradation will be explored via the identification of enzymes that can break down the carbamate bond. This will be through the development of microbial consortia/bacteria from enrichment experiments in hotbins set up two years ago, assays, DNA sequencing and enzyme identification. Also, informatics approaches and the use of databases, and metagenomic strategies including our metagenomics database. The polyester and Spandex degrading enzymes will then be combined and optimised using enzyme mutagenesis approaches and high throughput automated screening platforms. Using the best combination of enzymes, procedures will be tested to isolate the key aromatic acid and amine fragments, while the remaining soft segment components can potentially be used as a carbon feedstock for bioplastic production. A route to enhance the value of the amine fragment will also be explored using in house oxidative enzymes. Throughout the project and through links to the UCL Plastic Waste Innovation Hub we will assess the social, economic, and environmental impact of the technologies developed and gather the data for a life cycle analysis.