Divergent microbial structure still results in convergent microbial function during arrested anaerobic digestion of food waste at different hydraulic retention times

In this study, two arrested anaerobic digestion bioreactors fed with food waste operated under different hydraulic retention times (HRTs) exhibited long-term stable volatile fatty acid (VFA) production performance including similar total yields (p = .085) with propionic acid (PA) being the most abundant VFA. Meta-omics analysis revealed distinct microbial structures (p = .02) at the two HRTs while there were no differences in potential and extant functionality as indicated by the whole-genome and whole-transcriptome sequencing, respectively. The highest potential (relative abundance of DNA sequence reads) and extant (relative abundance of mRNA sequence reads) functionality corresponded with PA production compared to other acids. The most abundant genus Prevotella produced PA mainly through the acryloyl-CoA pathway. Based on our results, the mechanistic basis for the similar VFA production performance observed under the HRTs tested lies in the community-level redundancy in convergent acidification functions and pathways, rather than trends in community structure.