Microbial integration of plastics in the circular economy

在本提案中，我们将开发使用两种不可再生塑料聚合物（聚对苯二甲酸乙二醇酯（PET）和聚氨酯（PU））作为循环经济所需微生物转化原料的技术。特别是，我们将专注于将PET和PU废料转化为工业相关和更可持续的Bio-PU聚合物部分。通过这种方法，我们还将实现Bio-PU产品的回收利用，从而实现一种重要材料可持续生产的完全循环战略。PET作为包装材料的成功只能与其在环境中的降解能力相媲美。同样，聚氨酯的生产率也在增加，但需要注意的是，聚氨酯的回收程序几乎不存在。PET可以使用物理化学过程（例如热解）和最近的酶水解降解成组成单体。另一方面，PU在酶水解方面还没有得到很好的表征，但最近已经描述了微生物对聚合物的活性。Bio-PU所需单体的合成已经在不同生物体中使用标准碳源（例如葡萄糖）实现。在MIPLACE，我们将使用PET水解产物作为唯一的能源和碳源，通过生物转化合成它们。来自该联盟成员的初步结果表明，尽管产量较低，但这是可以实现的。尽管范围有限，但这些先前的观察结果支持PET和PU是细菌生长的可行基质。在本提案中，我们将扩展这些工作，并将PET和PU作为生物技术应用的一般基质，包括开发可以直接以PET和PU为唯一碳源的细菌群落，而无需事先进行裂解步骤。在MIPLACE中，我们设计了一种基于微生物群落的多学科策略，用于将PET和PU有效转化为Bio-PU。我们的工作流程基于工程学科的传统设计-构建-测试周期。我们将使用微生物的环境筛选，菌株的合理设计和实验室定向进化的组合来实现这一目标。我们建立在相关合作伙伴的互补优势之上，其中包括酶学，合成生物学，代谢工程，数学建模，化学工程和生物降解。与此同时，我们将解决与这项研究相关的社会问题，这些问题与公众对所采取方法的看法以及影响消费者行为变化的可能性有关。总体而言，MIPLACE将提供将塑料聚合物纳入循环经济所需的技术开发，为新的生物技术方法铺平了道路，这些方法基于一种材料，否则这种材料将被视为废物。通过开发高效的微生物PET转化工艺，我们的目标是以一种全新的方法利用这些废物流作为化石基碳源，用于生产增值材料，为增加报废塑料收集提供经济激励，以促进可持续的生物基经济。

In this proposal we will develop the technology required to use two recalcitrant plastic polymers, polyethylene terephthalate (PET) and polyurethane (PU) as feedstock for microbial transformations required for a circular economy. In particular, we will focus on the transformation of PET and PU waste into the industrially relevant and more sustainable moieties for Bio-PU polymers. With this approach we will also enable the recycling of the Bio-PU product, completing this way a fully circular strategy for the sustainable production of an important material.The success of PET as a packaging material is only comparable to its resilience to degradation in the environment. Likewise, production rates of PU are also increasing, with the caveat that the recycling procedures for PU are virtually non-existing. PET can be degraded to constituent monomers using physicochemical processes such as pyrolysis and, more recently, by enzymatic hydrolysis. PU, on the other hand, is not so well characterised in terms of enzymatic hydrolysis, but microbial activities against the polymer have been recently described.The synthesis of the monomers required for Bio-PU has been achieved using standard carbon sources (e.g. glucose) in different organisms. In MIPLACE we will synthesise them in biotransformations using the products of hydrolysis of PET as the sole energy and carbon source. Preliminary results from members in the consortium show that this can be achieved although with low yields.Despite their limited scope, these previous observations support that PET and PU are feasible substrates for bacterial growth. In this proposal we will expand on those works and establish PET and PU as general substrates for biotechnological applications including the development of bacterial communities that can directly feed on PET and PU as the sole carbon source without the need of a prior lytic step.In MIPLACE we have devised a multidisciplinary strategy based on the use of microbial communities for the effective transformation of PET and PU into Bio-PU. Our workflow is based on the traditional design-build-test cycle of engineering disciplines. We will use a combination of environmental screening of microorganisms, rational design of strains and lab directed evolution to achieve this goal. We build on the complementary strengths of the partners involved, which include enzymology, synthetic biology, metabolic engineering, mathematical modelling, chemical engineering and biodegradation. At the same time, we will address the societal concerns associated to this research that are related to the public perception of the approach taken and the possibility of influencing changes in consumer behaviour.Overall, MIPLACE will deliver the technological development required for incorporating plastic polymers in the circular economy, paving the way for new biotechnological approaches based on a material that would otherwise be condemned to end up as waste otherwise. By developing efficient microbial PET transformation processes, we aim to use these waste streams in a completely new approach as fossil-based carbon sources for the production of value-added materials, providing the economic incentive to increase end-of-life plastic collection in favour of a sustainable bio-based economy.