Abstract Anaerobic digestion is an important technology for the bio-based economy. The stability of the process is crucial for its successful implementation and depends on the structure and functional stability of the microbial community. In this study, the total microbial community was analyzed during mesophilic fermentation of sewage sludge in full-scale digesters. The digesters operated at 34–35°C, and a mixture of primary and excess sludge at a ratio of 2:1 was added to the digesters at 550 m3/d, for a sludge load of 0.054 m3/(m3·d). The amount and composition of biogas were determined. The microbial structure of the biomass from the digesters was investigated with use of next-generation sequencing. The percentage of methanogens in the biomass reached 21%, resulting in high quality biogas (over 61% methane content). The abundance of syntrophic bacteria was 4.47%, and stable methane production occurred at a Methanomicrobia to Synergistia ratio of 4.6:1.0. The two most numerous genera of methanogens (about 11% total) were Methanosaeta and Methanolinea, indicating that, at the low substrate loading in the digester, the acetoclastic and hydrogenotrophic paths of methane production were equally important. The high abundance of the order Bacteroidetes, including the class Cytophagia (11.6% of all sequences), indicated the high potential of the biomass for efficient degradation of lignocellulitic substances, and for degradation of protein and amino acids to acetate and ammonia. This study sheds light on the ecology of microbial groups that are involved in mesophilic fermentation in mature, stably-performing microbiota in full-scale reactors fed with sewage sludge under low substrate loading.

中文翻译：

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大型污水处理厂厌氧消化池的微生物群

摘要 厌氧消化是生物经济的一项重要技术。该过程的稳定性对其成功实施至关重要，并取决于微生物群落的结构和功能稳定性。在这项研究中，分析了污水污泥在全规模消化池中温发酵过程中的总微生物群落。消化池在 34-35°C 下运行，初级污泥和剩余污泥的混合物以 2:1 的比例以 550 m3/d 的速度加入消化池，污泥负荷为 0.054 m3/(m3·d)。确定了沼气的数量和组成。使用下一代测序研究了来自消化器的生物质的微生物结构。生物质中产甲烷菌的百分比达到了 21%，产生了高质量的沼气（甲烷含量超过 61%）。共养细菌的丰度为 4.47%，在甲烷微生物与协同作用的比例为 4.6:1.0 的情况下，产生稳定的甲烷。产甲烷菌中数量最多的两个属（约占总数的 11%）是 Methanosaeta 和 Methanolinea，这表明，在消化器中底物负荷较低的情况下，甲烷生产的醋酸碎屑和氢营养途径同样重要。拟杆菌目的高丰度，包括噬菌体类（占所有序列的 11.6%），表明生物质在有效降解木质纤维素物质以及将蛋白质和氨基酸降解为乙酸盐和氨方面具有很高的潜力。这项研究揭示了参与成熟中温发酵的微生物群的生态学，