Functional Redundant Microbiome Enhanced Anaerobic Digestion Efficiency under Ammonium Inhibition Conditions

Revealing the role of functional
redundancy is of great
importance considering its key role in maintaining the stability of
microbial ecosystems in response to various disturbances. However,
experimental evidence on this point is still lacking due to the difficulty
in “manipulating” and depicting the degree of redundancy.
In this study, manipulative experiments of functional redundancy were
conducted by adopting the mixed inoculation strategy to evaluate its
role in engineered anaerobic digestion systems under ammonium inhibition
conditions. The results indicated that the functional redundancy gradient
was successfully constructed and confirmed by evidence from pathway
levels. All mixed inoculation groups exhibited higher methane production
regardless of the ammonium level, indicating that functional redundancy
is crucial in maintaining the system’s efficiency. Further
analysis of the metagenome-assembled genomes within different functional
guilds revealed that the extent of redundancy decreased along the
direction of the anaerobic digestion flow, and the role of functional
redundancy appeared to be related to the stress level. The study also
found that microbial diversity of key functional populations might
play a more important role than their abundance on the system’s
performance under stress. The findings provide direct evidence and
highlight the critical role of functional redundancy in enhancing
the efficiency and stability of anaerobic digestion.