Understanding and enhancing plastics biodegrdation

减少塑料对环境的影响是一项紧迫的任务，需要新的基础和技术解决方案。部分解决方案是开发“更好”的塑料，为其预期用途精心设计，并提供适当的报废选择。这将包括由可再生资源制成的可堆肥和可回收材料，其成本和性能与目前的石油基等效材料相当，甚至更好。因此，过去几年对生物基和/或非耐用塑料（所谓的生物塑料）的需求不断增加。聚乳酸（PLA）是一种生物基聚酯，是可降解生物塑料的旗舰产品。由于其性能和长期发展，PLA的需求不断增加。目前，其全球年产量约为435 kT，预计到2026年产能将增加80%。至关重要的是，在过去的15年里，关于其寿命结束选项的声明的变化，从可生物降解（意味着在自然条件下完全降解二氧化碳，水和生物质）到工业可堆肥（在受控条件下降解，包括60摄氏度以上的温度，控制湿度和选定的微生物），突出了聚乳酸的降解程度，以及一般的生物塑料，知之甚少，需要关注。尽管付出了巨大的努力，聚乳酸在工业堆肥条件下的生物降解率仍然很低，这降低了其在堆肥设施中的接受度（例如，当聚乳酸用于一次性可堆肥包装并与混合食物垃圾一起收集时）。在家庭堆肥或土壤中（例如，当沉积在环境中时），聚乳酸在可持续的时间框架内不存在生物降解。在这个项目中，我们将设计定制的聚合物添加剂来增强PLA的堆肥。（例如通过促进微生物生长来加速生物降解过程）。我们建议，不仅要开发聚合物添加剂，还要将它们与新的工程微生物和酶结合起来，这些微生物和酶能够“更好”地工作（例如，更快，耐受更高的温度）或能够产生有用的附加值化学品（例如，新聚合物的起始块，所产生的堆肥的营养物质）。最终，我们提出的技术将提高聚乳酸的堆肥，为生物塑料的生物降解带来新的基本认识，并将有助于实现其在循环经济中的潜力。

Reducing the impact of plastics on our environment is an urgent task that needs new fundamental and technological solutions. Part of the solution is to develop "better" plastics,well-designed for their intended use and with appropriate end-of-life options. This will include compostable and recyclable materials made from renewable resources at a cost and performance comparable to, or even better than, current petro-based equivalents. Thus, the past few years have seen an increasing demand for bio-based and/or non-durable plastics, so-called bioplastics.Poly(lactic acid), or PLA, is a bio-based polyester and the flagship of degradable bioplastics.Due to its properties and long-standing development, there is an increasing demand for PLA. Its annual production is currently at ~435 kT worldwide and an expected production capacity increase of 80% is predicted by 2026. Crucially, the change in claims regarding its end of life options over the past 15 years, from being biodegradable (implying complete degradation to CO2, water and biomass in natural conditions) to industrially compostable (degradation incontrolled conditions, including temperatures above 60 degree centigrade, controlled humidity and selected microorganisms) highlight how much the degradation of PLA, and bioplastics in general, is poorly understood and requires attention.Despite significant efforts, the biodegradation rate of PLA in industrial compost conditions remains low, reducing its acceptance in composting facilities (e.g. when PLA is used in disposable compostable packaging and collected along with mixed food waste). In home compost or soil (e.g. when deposited in the environment), PLA biodegradation is inexistent over a sustainable timeframe.In this project, we will design bespoke polymeric additives to enhance the composting of PLA. (e.g. by promoting microorganism growth to speed up the biodegradation process). We propose, not only to develop polymeric additives, but also to combine them with newly engineered microorganisms and enzymes able to work "better" (e.g. faster, tolerant to higher temperatures) or able to lead to useful and added-values chemicals (e.g. starting blocks for new polymers, nutriments for the resulting compost).Ultimately, our proposed technologies will enhance the composting of PLA, bring new fundamental understanding to bioplastic biodegradation and will contribute to enabling their potential within a circular economy.