Selective survival of anaerobic digester microbes after C. bescii pretreatment of manure

Extremophilic biological pretreatment (EBP) of dairy manure using Caldicellulosiruptor bescii at 75°C dramatically alters the microbial community structure and activity in anaerobic digesters (ADs). This study evaluated microbial abundance and activity in manure, EBP, and ADs at industrial scales using 16S sequencing of rDNA and rRNA. Results revealed that bacterial communities remained largely active and resilient throughout the system, but acetoclastic methanogens were sensitive to EBP treatment and failed to reestablish in ADs. In contrast, hydrogenotrophic methanogens survived EBP and persisted in ADs, although these species are poorly suited to metabolize the acetate-rich products generated by C. bescii in pretreatment. We conclude that the acetate utilization of ADs preceded by EBP is likely to improve if supplemented with acetoclastic methanogens, such as those present in raw manure.