Microbial integration of plastics in the circular economy

在本提案中，我们将开发使用两种顽固塑料聚合物（聚对苯二甲酸乙二醇酯（PET）和聚氨酯（PU））作为循环经济所需的微生物转化原料所需的技术。特别是，我们将重点关注将PET和PU废物转化为与工业相关且更可持续的生物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，以这种方式完成一种重要材料可持续生产的全面循环战略。PET作为包装材料的成功只能与它在环境中降解的弹性相媲美。同样，PU的生产率也在增加，但需要注意的是，PU的回收程序实际上不存在。PET可以通过物理化学过程，如热解，以及最近的酶水解，降解为组成单体。另一方面，PU在酶水解方面没有很好地表征，但最近已经描述了针对聚合物的微生物活性。Bio-PU所需单体的合成已经在不同的生物中使用标准碳源（例如葡萄糖）实现。在MIPLACE，我们将利用PET水解产物作为唯一的能量和碳源，在生物转化中合成它们。联盟成员的初步结果表明，尽管产量低，但这是可以实现的。尽管它们的范围有限，但这些先前的观察结果支持PET和PU是细菌生长的可行底物。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底物，包括开发可以直接以PET和PU为唯一碳源而无需事先裂解步骤的细菌群落。在MIPLACE，我们设计了一个基于微生物群落的多学科战略，将PET和PU有效地转化为Bio-PU。我们的工作流程基于传统的工程学科的设计-构建-测试周期。我们将结合微生物的环境筛选，菌株的合理设计和实验室定向进化来实现这一目标。我们以合作伙伴的互补优势为基础，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，我们将处理与这项研究有关的社会关切，这些关切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。总的来说，MIPLACE将提供将塑料聚合物纳入循环经济所需的技术发展，为基于材料的新生物技术方法铺平道路，否则这些材料最终将被视为废物。通过开发高效的微生物PET转化过程，我们的目标是以一种全新的方法利用这些废物流作为生产增值材料的化石碳源，为增加报废塑料收集提供经济激励，有利于可持续的生物经济。

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.