Abstract: Anaerobic co-fermentation of straw and manure is a potential technique for biogas production. In this process, the spatial and temporal dynamics of prokaryotes associated to straw and sludge, and their correlations with bioreactor performance remain to be unveiled. To address these questions, prokaryotic compositions and dynamics associated to straw and sludge were investigated during co-fermentation of straw and swine manure using pyrosequencing technique. Co-fermentation of straw and swine manure contributed significantly to fermentation performance. Further analysis indicated that spatial distribution pattern of prokaryotes in the co-fermentation system might increase fermentation efficiency. Straw was digested by its associated microbiota, such as genera Treponema, Clostridium Ⅲ, Alkaliflexus and Fibrobacter, providing substrates for the production of volatile fatty acids (VFAs). Propionic acid was most abundant in the sludge. The genera Syntrophomonas, Pelotomaculum, Methanoculleus, Methanosarcina and Methanosaeta metabolize VFAs into methane syntrophically via both hydrogenotrophic and acetocalstic pathways. The genera Aminobacterium and Cloacibacillus involved in amino acid degradation were much abundant in the sludge, indicating that protein was an important substrate for methanogenesis. These findings suggested that spatial distribution of microbiota, steady straw-associated degraders and dynamic microbial communities in the sludge were vital for the performance of biogas co-fermentation system.

Key words: fermentation, straw, swine manure, 16S rRNA amplicon pyrosequencing, prokaryotic community

摘要： 秸秆与禽畜粪便混合发酵既可增强反应器稳定性又能提高发酵产气效率。然而关于秸秆附着菌群、发酵液菌群的时空动态变化，以及它们与产气效率、环境变量的关系仍然未被全部揭示。采用16S rRNA基因扩增子高通量测序技术，对这一问题进行了研究。结果显示，秸秆猪粪混合发酵能够改善沼气发酵的效率。原核微生物群落在空间上的差异分布可能有助于提升系统的效率。在产气高效的系统中，秸秆吸附菌群如Treponema、Clostridium Ⅲ、Alkaliflexus 和 Fibrobacter是主要的纤维素降解菌，提供底物给产酸菌。丙酸是发酵液中含量最丰富的挥发性脂肪酸（VFAs），Pelotomaculum可能是该系统主要的丙酸氧化菌，它们与Methanoculleus、Methanosarcina和Methanosaeta协同作用通过二氧化碳/氢营养型和乙酸营养型产甲烷途径，将包括丙酸在内的VFAs最终转化成甲烷。参与氨基酸代谢的Aminobacterium和Cloacibacillus广泛分布于发酵液中，表明蛋白质是一种重要的发酵底物，说明VFAs尤其是丙酸和氨基酸的互营代谢可能是秸秆猪粪混合发酵系统的重要过程。这些结果表明，功能菌群的空间分化、稳定的秸秆降解菌群和发酵液菌群的弹性变化有助于维持秸秆猪粪混合发酵系统的稳定性和提高发酵效率。

关键词: 发酵, 秸秆, 猪粪, 16S rRNA扩增子高通量测序, 原核微生物群落