Assessment of active methanogenic archaea in a methanol-fed upflow anaerobic sludge blanket reactor

Abstract

Methanogenic archaea enrichment of a granular sludge was undertaken in an upflow anaerobic sludge blanket (UASB) reactor fed with methanol in order to enrich methylotrophic and hydrogenotrophic methanogenic populations. A microbial community assessment, in terms of microbial composition and activity-throughout the different stages of the feeding process with methanol and acetate-was performed using specific methanogenic activity (SMA) assays, quantitative real-time polymerase chain reaction (qPCR), and high-throughput sequencing of 16S ribosomal RNA (rRNA) genes from DNA and complementary DNA (cDNA). Distinct methanogenic enrichment was revealed by qPCR of mcrA gene in the methanol-fed community, being two orders of magnitude higher with respect to the initial inoculum, achieving a final mcrA/16S rRNA ratio of 0.25. High-throughput sequencing analysis revealed that the resulting methanogenic population was mainly composed by methylotrophic archaea (Methanomethylovorans and Methanolobus genus), being also highly active according to the RNA-based assessment. SMA confirmed that the methylotrophic pathway, with a direct conversion of methanol to CH, was the main step of methanol degradation in the UASB. The biomass from the UASB, enriched in methanogenic archaea, may bear great potential as additional inoculum for bioreactors to carry out biogas production and other related processes.

Characterization and Dynamic Shift of Microbial Communities during Start-Up, Overloading and Steady-State in an Anaerobic Membrane Bioreactor

“…The abundance of unclassified, Acidobacteria , Bacteroidetes and Proteobacteria in the start-up operation in this study were consistent with a previous study [ 37 ]. The occurrence of Firmicutes (genus of Clostridium sensu stricto ) and Actinobacteria in the AnMBR at both start-up and overloading operation, showed their contribution to the hydrolysis and acidogenesis, similar to previous reported [ 38 ]. Figure 6 shows the archaea genera shift from the start-up, steady-state, overloading and recovery periods of the AnMBR.…”

“…The genus of Acinetobacter presented high relative abundance at the overloading operation ( Figure 7 ), in concurrence with high sulfur hydrogen detection in the AnMBR ( Figure 2 b). Previous research reported the Acinetobacter genus to oxidize the sulfur hydrogen (H 2 S) [ 38 ]. At the recovery stage, the peak value of biogas production reached a low level, but the COD removal reached again above 91%.…”

Growth and Break-Up of Methanogenic Granules Suggests Mechanisms for Biofilm and Community Development

“…A single granule contains a diverse and dynamic microbial community, capable of adapting to various changes in environmental conditions (McKeown et al, 2009;Cerrillo et al, 2016;Kuroda et al, 2016;Na et al, 2016;Zhu et al, 2017;Keating et al, 2018). Microbial cells are juxtaposed, and immobilized, within a complex matrix of extracellular polymeric substances (EPS) (MacLeod et al, 1995).…”

Anaerobic digestion and electromethanogenic microbial electrolysis cell integrated system: Increased stability and recovery of ammonia and methane

“…To stabilise the nucleic acid, especially RNA, samples were stored at -80 ºC. The inoculum of the cathode and the biofilm settled up on the anode had been characterised in previous work[44,50].Briefly, regarding eubacteria, the cathode inoculum was dominated by Bacteroidetes, Firmicutes and Synergistetes (61, 14 and 8%, respectively); Methanosarcinaceae (52%) was the predominant archaea family (methylotrophs genus, Methanomethylovorans and Methanolobus)[44]. In the case of MEC anode biofilm, Firmicutes, Bacteroidetes and Proteobacteria were the dominant eubacterial phyla (35, 30 and 11%, respectively), and the predominant archaea family was Methanotrichaceae, Simultaneous total genomic DNA and RNA (including rRNA) were extracted in triplicate from known weights of each sample, which consisted in effluent from the AD, a piece of carbon felt from the anode (1 cm 2 ) and granular graphite collected from the cathode compartments for the biocathode biofilm.…”