Improving process stability and kinetics of anaerobic biowaste digestion by promoting direct interspecies electron transfer among syntrophic microbial consortia

微生物将有机物转化为甲烷形式的可再生能源是有效废物管理的一种行之有效的广泛战略。在这种产生甲烷的环境中，电连接的细菌和古细菌进行直接的种间电子转移（DIET），作为种间氢或甲酸转移（IHT）的替代共生机制。然而，关于DIET的微生物生态学的基本方面仍不清楚，特别是其对沼气生产的意义仍有待阐明。迄今为止，研究主要集中在与中温上流式厌氧污泥毯（UASB）反应器处理废水相关的极少数模式生物的产甲烷共培养中的DIET。我们打算通过整合尖端的分子工具，如16S rRNA方法、宏基因组学和转录组学，以及基于培养的技术，在中温和嗜热消化器中产生更广泛适用的结构-功能关系知识，最终诱导更高的厌氧消化（AD）过程稳定性和效率。主要目标是鉴定能够进行DIET的新型生物，并了解DIET的遗传机制，重点是生物废物消化沼气工厂，这些工厂在反应器设置，操作模式，温度和底物组成方面与中温UASB反应器有很大不同。我们认为饮食是阿尔茨海默病中常见的IHT的共同选择。据我们所知，该项目将首次在嗜热系统和中温系统中同时研究DIET。我们进一步旨在确定在DIET过程中代谢的潜在底物，重点是对有机物厌氧分解至关重要的丙酸和丁酸合营养氧化联合体。宏基因组学将与转录组学一起用于重建代谢能力，以揭示与DIET相关的表达模式。氢的积累对整个过程的功能至关重要，一个避免氢产生的过程可能有利于AD的稳定性。因此，我们将专门丰富进行DIET的联合财团，并研究与IHT相比的生理优势。预期的结果将是充分利用AD潜力的必要步骤。鉴于DIET广泛分布在缺氧环境中，以及合作社区对代谢物有效转移的普遍需求，我们的研究结果也将与其他研究领域相关，例如减少产甲烷环境的温室气体排放和涉及电连接微生物的生物电化学系统。

Microbial conversion of organic matter to renewable energy in form of methane is a proven and widespread strategy for effective waste management. In such methane-producing environments, electrical connected bacteria and archaea perform direct interspecies electron transfer (DIET) as alternative syntrophic mechanism to interspecies hydrogen or formate transfer (IHT). However, fundamental aspects of the microbial ecology concerning DIET are still unclear, in particular, its significance for biogas production remains to be elucidated. To date, studies largely focused on DIET in methanogenic co-cultures of very few model organisms associated with mesophilic upflow anaerobic sludge blanket (UASB) reactors treating wastewaters. We intend to generate a more widely applicable knowledge of structure-function relationships within syntrophic core communities in mesophilic and thermophilic digesters by integrating cutting-edge molecular tools such as the 16S rRNA approach, metagenomics and transcriptomics with cultivation-based techniques to ultimately induce higher process stability and efficiency of anaerobic digestion (AD). Key objectives are the identification of novel organisms capable of DIET and to understand the genetic mechanisms underlying DIET with an emphasis on biowaste-digesting biogas plants that substantially differ from mesophilic UASB reactors in terms of reactor setup, mode of operation, temperature and substrate composition. We suggest that DIET is a co-occurring alternative to IHT common in AD. To our knowledge, the proposed project will target DIET for the first time in both thermophilic and mesophilic systems. We further aim to determine potential substrates metabolized during DIET focused on syntrophic propionate- and butyrate-oxidizing consortia that are of vital importance for the anaerobic breakdown of organic matter. Metagenomics will be used to reconstruct metabolic capabilities along with transcriptomics to reveal expression patterns associated with DIET. A process that circumvents the production of hydrogen, which accumulation can be critical to overall process functioning, may be beneficial for the stability of AD. Therefore, we will specifically enrich syntrophic consortia performing DIET and investigate physiological advantages over IHT. The anticipated results will represent an imperative step to exploit the full potential of AD. Given the fact that DIET is widely distributed in anoxic environments and the general need for efficient transfer of metabolites in cooperating communities our results will be relevant also to other fields of research such as reducing greenhouse gas emissions from methanogenic environments and bio-electrochemical systems where electrical connected microbes are implicated.