Abstract
SummaryThis study examined whether the abundance and expression of microbial 16S rRNA genes were associated with elemental concentrations and substrate conversion biokinetics in 20 full‐scale anaerobic digesters, including seven municipal sewage sludge (SS) digesters and 13 industrial codigesters. SS digester contents had higher methane production rates from acetate, propionate and phenyl acetate compared to industrial codigesters. SS digesters and industrial codigesters were distinctly clustered based on their elemental concentrations, with higher concentrations of NH 3‐N, Cl, K and Na observed in codigesters. Amplicon sequencing of 16S rRNA genes and reverse‐transcribed 16S rRNA revealed divergent grouping of microbial communities between mesophilic SS digesters, mesophilic codigesters and thermophilic digesters. Higher intradigester distances between Archaea 16S rRNA and rRNA gene profiles were observed in mesophilic codigesters, which also had the lowest acetate utilization biokinetics. Constrained ordination showed that microbial rRNA and rRNA gene profiles were significantly associated with maximum methane production rates from acetate, propionate, oleate and phenyl acetate, as well as concentrations of NH 3‐N, Fe, S, Mo and Ni. A co‐occurrence network of rRNA gene expression confirmed the three main clusters of anaerobic digester communities based on active populations. Syntrophic and methanogenic taxa were highly represented within the subnetworks, indicating that obligate energy‐sharing partnerships play critical roles in stabilizing the digester microbiome. Overall, these results provide new evidence showing that different feed substrates associate with different micronutrient compositions in anaerobic digesters, which in turn may influence microbial abundance, activity and function.
Highlights
Anaerobic digestion is a microbial process that produces renewable methane from various organic waste streams and is expanding globally due to a growing interest in sustainable energy and nutrient recovery (McCarty et al, 2011; Batstone and Virdis, 2014)
A co-occurrence network of ribosomal RNA (rRNA) gene expression confirmed the three main clusters of anaerobic digester communities based on active populations
These results provide new evidence showing that different feed substrates associate with different micronutrient compositions in anaerobic digesters, which in turn may influence microbial abundance, activity and function
Summary
Anaerobic digestion is a microbial process that produces renewable methane from various organic waste streams and is expanding globally due to a growing interest in sustainable energy and nutrient recovery (McCarty et al, 2011; Batstone and Virdis, 2014). Due to the large microbial biodiversity present in anaerobic digesters (Nelson et al, 2011; Sundberg et al, 2013) and the large portion of uncultured species in such systems (Li et al, 2009), culture-independent molecular tools have been critical in advancing our understanding of microbial communities within anaerobic digesters (Riviere et al, 2009; Werner et al, 2011; Vanwonterghem et al, 2014, 2016; De Vrieze et al, 2015, 2016a; Hao et al, 2016) Despite these advancements, anaerobic digesters are still typically operated based on empirical knowledge of process parameters, owing to a general lack of understanding regarding relationships between microbial community structure and digester function in terms of process biokinetics (Carballa et al, 2015).
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