Impact of substrate digestibility on microbial community stability in methanogenic digestors: The mechanism and solution

This study investigated the temporal dynamics of digestion efficiency and community stability in digesters fed with waste activated sludge (WAS), straw (STR-AD), food waste (FW-AD) and mixture of straw-and-food waste (STR-FW-AD). Results showed that carbon removals of recalcitrant substrates (i.e., 48.2 +/- 3.9% in WAS-AD and 57.8 +/- 4.9% in STR-AD) were lower than that of labile substrates (i.e., 70.7 +/- 4.0% in FW-AD). Nonetheless, carbon removal of recalcitrant substrates was largely improved through co-digestion (70.3 +/- 3.2% in STR-FWAD). In contrast to monopoly communities (e.g., the highly enriched Paludibacter) fed with the labile substrates, recalcitrant substrates supported highly diverse communities. Accordingly, the medians of negative/positive cohesions of communities in WAS-AD, STR-AD, STR-FW-AD and FW-AD decreased from 0.86 to 0.63, suggesting their decreasing community stability. Microbial source tracking analyses showed the major contribution of the STR-AD community to the co-digestion community. This study provided unprecedented mechanistic insight into stability improvement of substrate co-digestion on the methanogenic digestion microbiome.

Automated summary

This study investigated the temporal dynamics of digestion efficiency and community stability in digesters fed with different substrates. The results showed that co-digestion improved the carbon removal of recalcitrant substrates and supported highly diverse microbial communities.