Deep Understanding of the Methanogenic Community and Their Interaction in Batch High-Solid Anaerobic Digestion of Ensiled Straw with Leachate Circulation

High-solid anaerobic digestion (HS-AD) technology is a promising technique to treat organic residues because of its advantages of excellent processing capacity, less water usage, and small reactor volume. The efficiency of HS-AD is affected by mass transfer and other environmental factors, which reflect the variation of microbial communities. Revealing the relationship among the variations to the operational parameters of HS-AD will sharpen the strategies of HS-AD and raise efficiency. However, the methanogenic community of HS-AD is much more complicated than conventional liquid AD (L-AD) because of its limit of mass transfer. It is therefore important to reveal the interactions among those factors on AD performance and variation of the microbial community to enlighten the operational strategies. In this study, three leach bed reactors (LBRs) feeding of ensiled straw were operated with the leachate circulation. High-throughput sequencing was applied to monitor the dynamics of the methanogenic community and their interactions. Results demonstrated that mass transfer had only a limited impact on the methanogenic community. In addition, the species that adapt quickly to the environment could survive in batch cultivation, which shortened the lag time and improved process stability. Co-occurrence network and statistical analysis suggested that symbiosis was the principle of most of the surviving species, while the interspecies competition of the dominated species guided the community assembly. This study revealed the impact of environmental factors and the interactive principle of species, which could enhance the understanding of methanogenesis in HS-AD.