Department of Mechanical and Process Engineering, Institute of Bioprocess Engineering, Technical University Kaiserslautern, 67663, Kaiserslautern, Germany.
Department of Life Science Engineering, Institute of Bioprocess Engineering and Pharmaceutical Technology, Technische Hochschule Mittelhessen, 35390, Giessen, Germany.
Appl Microbiol Biotechnol. 2022 Jun;106(12):4427-4443. doi: 10.1007/s00253-022-12031-9. Epub 2022 Jun 28.
The electrochemical process of microbial electrosynthesis (MES) is used to drive the metabolism of electroactive microorganisms for the production of valuable chemicals and fuels. MES combines the advantages of electrochemistry, engineering, and microbiology and offers alternative production processes based on renewable raw materials and regenerative energies. In addition to the reactor concept and electrode design, the biocatalysts used have a significant influence on the performance of MES. Thus, pure and mixed cultures can be used as biocatalysts. By using mixed cultures, interactions between organisms, such as the direct interspecies electron transfer (DIET) or syntrophic interactions, influence the performance in terms of productivity and the product range of MES. This review focuses on the comparison of pure and mixed cultures in microbial electrosynthesis. The performance indicators, such as productivities and coulombic efficiencies (CEs), for both procedural methods are discussed. Typical products in MES are methane and acetate, therefore these processes are the focus of this review. In general, most studies used mixed cultures as biocatalyst, as more advanced performance of mixed cultures has been seen for both products. When comparing pure and mixed cultures in equivalent experimental setups a 3-fold higher methane and a nearly 2-fold higher acetate production rate can be achieved in mixed cultures. However, studies of pure culture MES for methane production have shown some improvement through reactor optimization and operational mode reaching similar performance indicators as mixed culture MES. Overall, the review gives an overview of the advantages and disadvantages of using pure or mixed cultures in MES. KEY POINTS: • Undefined mixed cultures dominate as inoculums for the MES of methane and acetate, which comprise a high potential of improvement • Under similar conditions, mixed cultures outperform pure cultures in MES • Understanding the role of single species in mixed culture MES is essential for future industrial applications.
微生物电合成（MES）的电化学过程用于驱动电活性微生物的新陈代谢，以生产有价值的化学品和燃料。MES 结合了电化学、工程学和微生物学的优势，提供了基于可再生原料和可再生能源的替代生产工艺。除了反应器概念和电极设计外，所使用的生物催化剂对 MES 的性能有重大影响。因此，可以将纯培养物和混合培养物用作生物催化剂。通过使用混合培养物，生物体之间的相互作用，如直接种间电子转移（DIET）或共营养相互作用，会影响 MES 的性能，表现在生产力和产物范围方面。本综述重点比较了微生物电合成中纯培养物和混合培养物。讨论了这两种方法的性能指标，如生产力和库仑效率（CE）。MES 的典型产物是甲烷和乙酸盐，因此这些过程是本综述的重点。一般来说，大多数研究都使用混合培养物作为生物催化剂，因为混合培养物在这两种产物中表现出更高的性能。当在等效的实验设置中比较纯培养物和混合培养物时，混合培养物可以实现 3 倍更高的甲烷和近 2 倍更高的乙酸盐生产速率。然而，通过反应器优化和操作模式进行的纯培养物 MES 产甲烷研究表明，其性能指标与混合培养物 MES 相似，已经取得了一些改善。总的来说，该综述概述了在 MES 中使用纯培养物或混合培养物的优缺点。关键点：• 未定义的混合培养物作为甲烷和乙酸盐 MES 的接种物占主导地位，具有很大的改进潜力。• 在相似条件下，混合培养物在 MES 中的性能优于纯培养物。• 了解混合培养物 MES 中单一物种的作用对于未来的工业应用至关重要。
