Collaborative Research: Biocatalytic Alcoholysis of PET in Nonaqueous Solvents for Polymer Recycling

合作研究：PET在非水溶剂中生物催化醇解用于聚合物回收

• 批准号: 2309899
• 负责人: Jason Berberich
• 金额: $ 33.14万
• 依托单位: Miami University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2309899&HistoricalAwards=false
• 关键词: Collaborative; Research; Biocatalytic; Alcoholysis; PET

With the accumulation of plastics in the environment being one of the most pressing societal challenges today, the development of methods to improve plastics recycling is crucial. A major challenge to plastics recycling is developing processes that are cost effective and yield polymers with properties that are identical to or better than those of the original plastic. While the use of biological catalysts for polymer recycling and upcycling has generated significant interest, research has been restricted to reactions that take place in water. Due to the limitations of water as a medium for such reactions, new approaches that improve the efficiency and conversion of plastic waste using biologically based methods are needed. The overall aim of this work is to explore the use of natural enzymes to deconstruct common single-use plastics such as polyethylene terephthalate (PET – commonly used in clothing fibers and liquid/food containers) in the absence of bulk water. This work will specifically leverage the dramatically improved properties of enzymes in “dry” environments, including the ability to catalyze a range of reactions that are not possible in aqueous media. This research will investigate enzymes that potentially can degrade PET in new ways that facilitate the repolymerization of the reaction products, which is critical for recycling. This effort will lead to a detailed understanding of the reaction parameters that impact enzyme efficiency in converting PET waste into useful, recycled plastics building blocks. This research will broaden participation in STEM research by engaging a diverse group of undergraduate and high school students in this research program. Participants will be recruited through a variety of programs, including the Summer Multicultural Access to Research Training (SMART) and STEM Routes programs at CU Boulder and Miami University. Moreover, meaningful teaching modules will be developed that can be incorporated into K-12 curricula on the biodegradation of materials and biocatalysis.The objective of this proposal is to develop a novel biocatalytic process for the deconstruction of polyethylene terephthalate (PET) plastics based on the alcoholysis of ester bonds in the polymer backbone by lipase. Of specific interest is correlating the kinetics of PET alcoholysis with the thermodynamics of the depolymerization reaction as well as the solvent properties, which enable the rate of alcoholysis to be fine-tuned. A major advantage of this approach over the hydrolysis of PET is that the use of nonaqueous media may promote swelling of the polymer, thereby increasing plasticity of the polymer chains. This in turn will increase the accessibility of the ester linkages in the polymer backbone and thus may significantly enhance the rate of biocatalytic conversion. Additionally, the use of nonaqueous solvents over water increases the ease of separation of the reaction products and can enhance the thermostability of the enzymes. These advantages potentially will eliminate the need for the high reaction temperatures as well as energy intensive pretreatment steps, such as melt extrusion and microgrinding, used in current PET recycling approaches. This work will specifically test the hypothesis that esterases can catalyze the alcoholysis of PET in nonaqueous media, and that the rate of alcoholysis can be controlled by varying the thermodynamic equilibrium water activity of the reaction as well as the solvent properties and choice of alcohol as the nucleophile. These studies will use lipase, including cutinase, as a model esterase since it is already well established that lipases can catalyze alcoholysis reactions in anhydrous media and bind to PET. Additionally, to correlate the kinetics of PET alcoholysis with the thermodynamics of the reaction, water activity will be controlled using salt hydrates. Finally, as part of this effort, rational strategies will be developed to reduce diffusional limitations of lipase in nonaqueous solvents, including ion pairing with surfactants. While this effort will focus on PET recycling, the proposed approach may be applicable in recycling of other synthetic polyesters. Moreover, the fundamental understanding of depolymerization reaction mechanisms developed by this this research program also may lead to new ways to chemically modify polyesters to improve their utility and recyclability.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

由于环境中塑料的积累是当今最紧迫的社会挑战之一，改善塑料回收的方法的发展至关重要。塑料回收的一个主要挑战是开发具有成本效益的过程，并产生与原始塑料相同或更好的特性的产量聚合物。虽然将生物催化剂用于聚合物回收和升级引起了极大的兴趣，但研究仅限于在水中发生的反应。由于水作为这种反应的介质的局限性，需要使用基于生物学的方法提高塑料废物效率和转化的新方法。这项工作的总体目的是探索使用天然酶来解构常见的一次性塑料，例如在没有散装水的情况下，聚对苯二甲酸酯（PET - 通常用于衣物纤维和液体/食品容器）。工作将特别利用酶在“干”环境中的动态改进特性，包括能够催化一系列在水性介质中不可能的反应的能力。这项研究将调查可能以新的方式降低宠物的酶，以维持反应产物的重新聚合，这对于回收至关重要。这项工作将导致对影响酶效率转化为有用的回收塑料构件的酶效率的反应参数的详细理解。这项研究将通过与该研究计划中的一群本科生和高中生一起吸引潜水者，从而扩大参与STEM研究的参与。参与者将通过各种计划招募，包括夏季多元文化获得研究培训（SMART）和CU Boulder和迈阿密大学的STEM路线计划。此外，有意义的教学模块该提案的目的是开发一种基于脂肪酶聚合物骨架中酯键的酗酒的聚对苯二甲酸酯（PET）塑料的解构的新型生物催化过程。特定感兴趣的是将宠物酒精分析的动力学与沉积反应的热力学以及溶液特性相关联，这使酒精中毒的速率得到微调。这种方法比PET水解的主要优点是，使用非水培养基可能会促进聚合物的肿胀，从而增加聚合物链的可塑性。反过来，这将增加聚合物主链中酯键的可及性，因此可能会显着提高生物催化转化率的速率。另外，在水上使用非水溶液可以提高反应产物的分离易度性，并可以增强酶的热稳定性。这些优势可能会消除对当前PET回收方法中使用的高反应温度以及能量密集型预处理步骤的需求。这项工作将特别检验以下假设：酯酶可以催化非水培养基中PET的酒精分析，并且可以通过改变反应的热力学平衡水活性以及溶液特性以及酒精作为核水合物的选择来控制酒精分析的速率。这些研究将使用脂肪酶，包括切碎酶作为模型酯酶，因为已经确定脂肪酶可以催化无水培养基中的酗酒反应并与PET结合。此外，为了将宠物酗酒的动力学与反应的热力学相关，将使用盐水合物控制水活性。最后，作为这项工作的一部分，将制定理性策略，以减少非水溶液中脂肪酶的差异局限性，包括与表面活性剂配对。尽管这种努力将集中在宠物回收上，但提出的方法可能适用于其他合成多植物的回收。此外，该研究计划开发的对沉积反应机制的基本理解也可能导致化学修改多植物以改善其实用性和可回收性的新方法。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响审查标准来通过评估来获得的支持。