The microbial functional gene diversity in anaerobic digesters under different organic loadings. sludge metagenome

Anaerobic digestion is a popular and effective microbial process for waste treatment. The performance of anaerobic digestion processes is contingent on the balance of the microbial food web in utilizing various substrates. Recently, co-digestion, i.e., supplementing the primary substrate with an organic-rich co-substrate has been exploited to improve waste treatment efficiency. Yet the potential effects of elevated organic loading on microbial functional gene community remains elusive. In this study, functional gene array (GeoChip 5.0) was used to assess the response of microbial community to the addition of poultry waste in anaerobic digesters treating dairy manure. Consistent with 16S rRNA gene sequences data, GeoChip data showed that microbial community compositions were significantly shifted in favor of copiotrophic populations by co-digestion, as taxa with higher rRNA gene copy number such as Bacilli were enriched. The acetoclastic methanogen Methanosarcina was also enriched, while Methanosaeta was unaltered but more abundant than Methanosarcina throughout the study period. The microbial functional diversity involved in anaerobic digestion were also increased under co-digestion. Overall design: There were two sets of anaerobic digesters. Three control digesters were fed with dairy manure and the organic loading rate kept constant. The three treatment digesters were fed with poultry waste in addition to dairy manure, resulting in step-wise increase in the organic loading rate. Sludge samples were taken at different time points from the six digesters.

厌氧消化（Anaerobic Digestion）是一种应用广泛且高效的废弃物处理微生物工艺。厌氧消化工艺的性能取决于微生物食物网在利用各类底物时的动态平衡。近年来，共消化（co-digestion）策略——即向主底物中添加富含有机物的共底物——被广泛应用以提升废弃物处理效率。然而，有机负荷升高对微生物功能基因群落的潜在影响仍尚不明确。本研究采用功能基因芯片（GeoChip 5.0），评估了处理奶牛粪便的厌氧消化器中添加家禽废弃物后，微生物群落的响应特征。与16S核糖体RNA基因（16S rRNA gene）测序数据一致，功能基因芯片数据显示，共消化显著重塑了微生物群落组成，使其向富营养型类群倾斜：例如16S rRNA基因拷贝数较高的芽孢杆菌纲（Bacilli）类群显著富集。乙酸型产甲烷古菌甲烷八叠球菌属（Methanosarcina）同样得到富集，而甲烷鬃菌属（Methanosaeta）未发生明显丰度变化，但在整个研究周期内其丰度始终高于甲烷八叠球菌属。共消化条件下，参与厌氧消化过程的微生物功能多样性亦有所提升。整体实验设计：本研究设置两组厌氧消化装置，其中3个对照消化器仅以奶牛粪便为底物，有机负荷率维持恒定；3个处理组消化器在奶牛粪便底物基础上额外添加家禽废弃物，导致有机负荷率逐步升高。研究人员于不同时间点从6个消化器中采集污泥样品。