Multistep Bioelectrochemical Reaction Cascade in Continuously Operated Flow Reactors (BioElectroFlow)

该项目的主要目的是阐明在连续操作的流动反应器中实现多步生物电化学反应级联的关键科学问题。从分批设置的AIO电极过渡到连续操作的生物电化学过程，从第一个项目阶段建立的一步生物电化学系统开始。这将扩展到一个三步生物电化学级联反应，即在两种不同的非特异性过氧酶(UPO)的催化下，5-羟甲基呋喃(HMF)氧化成有价值的2，5-呋喃二酸(FDCA)。这种串联装置将允许通过不同的反应器配置、操作点以及酶/电极相互作用的系统性质来详细研究不同的稳态条件。反应器级联可在电极表面使用固定化UPO作为一系列推流反应器(PFR)和连续操作的搅拌釜式反应器(CSTR)循环回路反应器。或者，可以施加均质溶解的UPO，这些UPO通过再循环流中的附加超滤膜单元进行回收。通过这两种根本不同的反应器叶栅结构，将加深对影响关键性能参数的理解。此外，前一个项目中指出的挑战将通过设计改进的多孔球石墨(GG)电极来解决。主要目标是提高过氧化氢的产量和法拉第效率(F.E.)。将探索几种方法，例如改变聚乙烯醇缩丁醛(PVB)含量以影响GG的孔隙率，以及实施多个分段式GG模块。后者可以通过隔离的方式分开，也可以作为不同孔隙度的单元相连。这将允许PFR设置中所需的过氧化氢生成速率的梯度，以最大限度地减少过氧化氢的积累和酶的失活。将讨论以下关键科学问题：·流动反应器的几何形状和增加的流量如何影响电极间/通过电极的传质、可能的扩散限制以及酶的稳定性？·GG的形态需要如何随聚乙烯醇缩丁醛(PVB)含量的变化而变化，·如何通过热处理和/或壁厚来提高GG电极的耐久性，使其能够承受内部气体压力？·如何设计分段石墨电极，使其能够在过氧化氢产生率中实现长度梯度？·不同的反应器运行模式(例如，间歇、PFR、CSTR)和由此产生的不同的线性流速如何影响性能指标，如总周转次数(TTN)、周转频率(TOF)、酶失活常数和生产率？

The main objective of this project is to elucidate the key scientific questions to enable multistep bioelectrochemical reaction cascades in continuously operated flow reactors. The transition from AiO electrode setup in a batch to a continuously operated bioelectrochemical process starts from the established one-step bioelectrochemical system in the first project phase. This will be extended to a three-step bioelectrochemical reaction cascade, the oxidative valorization of 5-hydroxymethylfurfural (HMF) to valuable 2,5-furandicarboxylic acid (FDCA) catalyzed by two different unspecific peroxygenases (UPO). This cascade setup will allow the detailed study of different steady-state conditions through different reactor configurations, operating points as well as systematic properties of enzyme/electrode interactions. The reactor cascade can be operated with immobilized UPOs on the electrode surface as a sequence of plug flow reactors (PFR) as well as circulation loop reactors in continuously operated stirred tank reactor mode (CSTR). Alternatively, homogeneously solubilized UPOs can be applied that are recycled via an additional ultrafiltration membrane unit in the recirculation stream. By these two fundamental different reactor cascade configurations, a deepened understanding on affecting key performance parameters will be generated. Furthermore, challenges pointed out in the previous project will be addressed by designing improved porous Globugraphite (GG) electrodes. Key objective is to improve H2O2 productivity and Faradaic efficiency (F.E.). Several approaches will be explored, such as varying the polyvinyl butyral (PVB) content to influence the porosity of the GG and implementing multiple segmented GG modules. The latter ones might be separated by isolation or connected as units of different porosity. This will allow for a gradient of the H2O2 generation rate needed in a PFR setup to minimize H2O2 accumulation and enzyme deactivation. The following key scientific questions will be addressed: • How do the flow reactor geometry and increased flow rate influence mass transfer across/through the electrode, possible diffusion limitation as well as enzyme stability? • How does the morphology of the GG need to be varied by polyvinyl butyral (PVB) content, ZnO particle size and wall thickness to affect pore size in a way to maximize / tailor H2O2 productivity and F.E.? • How can the durability of GG electrodes be increased by thermal treatment and/or wall thickness to withstand the internal gas pressure? • How is a segmented graphite electrode to be designed to enable a length gradient in H2O2 generation rate? • How do different reactor operation modes (e.g. batch, PFR, CSTR) and resulting different linear flow rates influence performance indicators such as total turnover number (TTN), turnover frequency (TOF), enzyme deactivation constants and productivity?