Microbial communities in Caldicellulosiruptor spp. pretreatment vessels and anaerobic digesters fed dairy manure
Listed in
This article is not in any list yet, why not save it to one of your lists.Abstract
The composition of microbial communities was determined in commercial-scale vessels used for 1) hyperthermophilic pretreatment (EBP) of dairy manure with four species of Caldicellulosiruptor spp at 70–72⁰C, 2) anaerobic digestion of 8% manure in continuously stirred tank reactors (CSTRs) at 35– 37°C, and 3) anaerobic digestion at 35-37⁰C in induced bed reactors (IBRs) fed a mixture of effluents from EBPs and CSTRs. Samples were collected approximately weekly for 60 days. pH, volatile fatty acid anion and bicarbonate concentrations, COD, and methane yield were measured to assess environmental conditions. Microbial community compositions were obtained via 16S rRNA gene sequencing. Caldicellulosiruptor spp. pretreatment altered microbial composition and amplified community connectivity in the IBRs which enhanced syntrophic methanogenesis. Methanobacteriaceae, Methanobrevibacter , and Methanosarcina were the main methanogenic taxa detected in all reactors. Methanogenic Methanothermobacter and Candidatus Methanoplasma were uniquely associated with pretreated digestate. Co-occurrence network analysis of pretreated manure in EBP tanks and IBRs revealed dense community interactions, with methylotrophic Methanosphaera and hydrogenotrophic Methanobrevibacter strongly connected to syntrophic bacteria capable of H 2 production. Raw manure and CSTR community networks were loose and disconnected and exhibited higher modularity. Acetoclastic methanogens did not display co-occurrence relationships with other taxa due to high acetate concentrations in the raw manure and EBP effluent.
Importance
Anaerobic digestion of dairy manure is limited by incomplete hydrolysis of recalcitrant substrates and insufficient syntrophic interaction among microbial taxa. This study examines the impact of hyperthermophilic Caldicellulosiruptor spp. pretreatment on microbial community structure and interface across multiple reactor types in a commercial-scale system. Results show that pretreatment alters methanogenic pathways, selecting for syntrophic archaea and amplifying network connectivity in downstream digesters. These findings provide insights into the microbial basis of improved methane production following pretreatment and suggest network structure as a useful metric for evaluating reactor performance.
