Anaerobic digestion (AD) has been proven to be an effective green technology for producing biomethane while reducing environmental pollution. The interspecies electron transfer (IET) processes in AD are critical for acetogenesis and methanogenesis, and these IET processes are carried out via mediated interspecies electron transfer (MIET) and direct interspecies electron transfer (DIET). The latter has recently become a topic of significant interest, considering its potential to allow diffusion-free electron transfer during the AD process steps. To date, different multi-heme c-type cytochromes, electrically conductive pili (e-pili), and other relevant accessories during DIET between microorganisms of different natures have been reported. Additionally, several studies have been carried out on metagenomics and metatranscriptomics for better detection of DIET, the role of DIET's stimulation in alleviating stressed conditions, such as high organic loading rates (OLR) and low pH, and the stimulation mechanisms of DIET in mixed cultures and co-cultures by various conductive materials. Keeping in view this significant research progress, this study provides in-depth insights into the DIET-active microbial community, DIET mechanisms of different species, utilization of various approaches for stimulating DIET, characterization approaches for effectively detecting DIET, and potential future research directions. This study can help accelerate the field's research progress, enable a better understanding of DIET in complex microbial communities, and allow its utilization to alleviate various inhibitions in complex AD processes.

中文翻译：

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厌氧消化中种间电子直接传递的微生物群落、机制及刺激效应研究进展


厌氧消化（AD）已被证明是生产生物甲烷同时减少环境污染的有效绿色技术。 AD中的种间电子转移（IET）过程对于乙酸生成和产甲烷至关重要，这些IET过程是通过介导的种间电子转移（MIET）和直接种间电子转移（DIET）进行的。考虑到其在 AD 工艺步骤中实现无扩散电子转移的潜力，后者最近已成为人们广泛关注的话题。迄今为止，已经报道了不同性质的微生物在饮食期间存在不同的多血红素c型细胞色素、导电菌毛（e-pili）和其他相关附件。此外，为了更好地检测 DIET、DIET 刺激在缓解高有机负荷率 (OLR) 和低 pH 等应激条件中的作用，以及 DIET 在混合培养物中的刺激机制，还开展了宏基因组学和宏转录组学方面的多项研究以及各种导电材料的共培养。鉴于这一重大研究进展，本研究深入了解了 DIET 活性微生物群落、不同物种的 DIET 机制、刺激 DIET 的各种方法的利用、有效检测 DIET 的表征方法以及未来潜在的研究方向。这项研究有助于加速该领域的研究进展，更好地了解复杂微生物群落中的饮食，并利用其减轻复杂 AD 过程中的各种抑制。