Archaeal community composition affects the function of anaerobic co-digesters in response to organic overload

Abstract

Microbial community diversity in two thermophilic laboratory-scale and three full-scale anaerobic co-digesters was analysed by genetic profiling based on PCR-amplified partial 16S rRNA genes. In parallel operated laboratory reactors a stepwise increase of the organic loading rate (OLR) resulted in a decrease of methane production and an accumulation of volatile fatty acids (VFA). However, almost three-fold different OLRs were necessary to inhibit the gas production in the reactors. During stable reactor performance, no significant differences in the bacterial community structures were detected, except for in the archaeal communities. Sequencing of archaeal PCR products revealed a dominance of the acetoclastic methanogen Methanosarcina thermophila, while hydrogenotrophic methanogens were of minor importance and differed additionally in their abundance between reactors. As a consequence of the perturbation, changes in bacterial and archaeal populations were observed. After organic overload, hydrogenotrophic methanogens (Methanospirillum hungatei and Methanoculleus receptaculi) became more dominant, especially in the reactor attributed by a higher OLR capacity. In addition, aggregates composed of mineral and organic layers formed during organic overload and indicated tight spatial relationships between minerals and microbial processes that may support de-acidification processes in over-acidified sludge. Comparative analyses of mesophilic stationary phase full-scale reactors additionally indicated a correlation between the diversity of methanogens and the VFA concentration combined with the methane yield. This study demonstrates that the coexistence of two types of methanogens, i.e. hydrogenotrophic and acetoclastic methanogens is necessary to respond successfully to perturbation and leads to stable process performance.

Stable carbon isotopes of methane for real‐time process monitoring in anaerobic digesters

“…The enrichment about 25‰ in δ 13 C CH4 possibly indicates a shift from a dominance of hydrogenotrophic methanogenesis to a dominance of acetototrophic methanogenesis, which would also explain the strong acetate consumption. A change in archaeal community composition due to organic overload was also recently observed by Lerm et al [24] who studied the microbial composition of full-scale and lab-scale biogas plants filled with sludge and organic waste. Munk et al [25] who studied microbial population dynamics during acidification of maize digesters observed a dominance of the hydrogenotrophic microbial community under conditions of high organic load, which would also support the possibility that phases 1 and 2 were dominated by hydrogenotrophic methanogenesis.…”

Bacterial community dynamics in a swine wastewater anaerobic reactor revealed by 16S rDNA sequence analysis

“…Previous studies have investigated the effects of organic shock loading on the microbial communities in anaerobic digesters (Delbès et al, 2001;Akuzawa et al, 2011;Gomez et al, 2011;Steinberg and Regan, 2011;Kundu et al, 2012;Lerm et al, 2012;Xia et al, 2012). Based on these studies, specific bacterial and archaeal groups that can tolerate or even take advantage of a higher concentration of acetate and volatile fatty acids increase in dominance and may help to stabilize the system.…”

Anaerobic digestion performance of vinegar residue in continuously stirred tank reactor

“…accumulated in the process of hydrolysis and acidification will ultimately lead to irreversible acidification (Nagao et al, 2012). High organic loading could lead to collapse of the subsequent biogas production system, a long time of recovery, or complete replacement of the materials within the reactor, so reactors are usually not run in highest OLR (Lerm et al, 2012). The effects of OLR on the AD of vinegar residue remain unclear.…”