Methanogen

About: Methanogen is a research topic. Over the lifetime, 1146 publications have been published within this topic receiving 48254 citations.

Development of Bioreactors for Enrichment of Chemolithotrophic Methanogen and Methane Production

Abstract: A gas-circulating bioreactor was used for enrichment of autotrophic methanogens. Mixture of hydrogen and carbon dioxide (5:1) was used as a sole energy and carbon source. Anaerobic digestive sludge isolated from wastewater treatment system was inoculated into the gas-circulating bioreactor. The enrichment of two chemolithotrophic methanogens, Methanobacterium curvum and Methanobacterium oryzae was accomplished in the gas-circulating bioreactor. The enriched bacteria were cultivated in a bioreactor equipped with hollow-fiber hydrogen-supplying system (hollow-fiber bioreactor), and a hybrid-type bioreactor equipped with hollow-fiber hydrogen-supplying system and electrochemical redox control system. The methane productivity was maximally 30% (V/V) in the hollow-fiber bioreactors and 50% (V/V) in the hybrid-type bioreactor.

Effect of the macroalgae Asparagopsis taxiformis on methane production and the rumen microbiome assemblage

Abstract: Background Recent studies using batch-fermentation suggest that the red macroalgae Asparagopsis taxiformis might reduce methane (CH4) emission from beef cattle by up to ∼99% when added to rhodes grass hay, a common feed in the Australian beef industry. These experiments have shown significant reductions in methane without compromising other fermentation parameters (i.e. volatile fatty acid production) with A. taxiformis organic matter (OM) inclusion rates of up to 5%. In the study presented here, A. taxiformis was evaluated for its ability to reduce methane production from dairy cattle fed a mixed ration widely utilized in California; the largest milk producer in the US. Results Fermentation in a semi-continuous in-vitro rumen system suggests that A. taxiformis can reduce methane production from enteric fermentation in dairy cattle by 95% when added at a 5% OM inclusion rate without any obvious negative impacts on volatile fatty acid production. High-throughput 16S ribosomal RNA (rRNA) gene amplicon sequencing showed that seaweed amendment effects rumen microbiome communities consistent with the Anna Karenina hypothesis, with increased beta-diversity, over time scales of approximately three days. The relative abundance of methanogens in the fermentation vessels amended with A. taxiformis decreased significantly compared to control vessels, but this reduction in methanogen abundance was only significant when averaged over the course of the experiment. Alternatively, significant reductions of methane in the A. taxiformis amended vessels was measured in the early stages of the experiment. This suggests that A. taxiformis has an immediate effect on the metabolic functionality of rumen methanogens whereas its impact on microbiome assemblage, specifically methanogen abundance, is delayed. Conclusions The methane reducing effect of A. taxiformis during rumen fermentation makes this macroalgae a promising candidate as a biotic methane mitigation strategy in the largest milk producing state in the US. But its effect in-vivo (i.e. in dairy cattle) remains to be investigated in animal trials. Furthermore, to obtain a holistic understanding of the biochemistry responsible for the significant reduction of methane, gene expression profiles of the rumen microbiome and the host animal are warranted.

Biodegradation of Anaerobic, Alkaline Cellulose Degradation Products

Abstract: The proposed strategy for the disposal of the United Kingdom’s nuclear waste inventory is placement within a deep geological disposal facility (GDF). The prevailing conditions of a GDF are expected to be anaerobic, with alkaline conditions (10.5 13) over a long timescale. In these anaerobic, alkaline conditions the cellulosic components of intermediate level wastes are expected to degrade, with the major products being the α- and β-forms of isosaccharinic acid (ISA). ISAs have received particular attention because of their ability to form complexes with radionuclides, potentially influencing their migration through the GDF. The potential for microbial colonisation of a GDF means that ISAs present a source of organic carbon for utilisation. The ability of micro-organisms to utilise cellulose degradation products including ISA is poorly understood. The work presented in this thesis has shown that near surface microbial consortia are capable of the degradation of ISA under iron reducing, sulphate reducing and methanogenic conditions at circumneutral pH values expected within geochemical niches of the near field and far field of a facility, with PCR analysis suggesting groups responsible for these metabolic processes were present in each instance. The same near surface consortium studied was capable of ISA degradation up to a pH of 10 within 8 weeks. Degradation rates were retarded by the increase in pH, in particular that of the β- stereoisomer. Clostridia were the likely bacterial Class responsible for fermentation of ISA to acetic acid, carbon dioxide and hydrogen. These secondary metabolites were then used in the generation of methane by methanogenic Archaea, however the acetoclastic methanogen component of the consortium was absent at elevated pH; evidenced by the persistence of acetic acid within the microcosm chemistry. The mesophilic consortium used in these initial investigations was not capable of ISA degradation above pH 10 within the short timescales imposed within the project. As a result, a soil consortium was obtained from a hyper alkaline contaminated site, where waste products from lime burning had occurred between 1883 and 1944. Initial surveying of the site showed that ISA was present and generated through interactions between the hyperalkaline leachate and organic soil matter. Following sub-culture of the soil consortia at pH 11, complete ISA degradation was observed within 14 days where again, fermentation processes followed by methanogenesis occurred. Clone libraries showed that again Clostridia was the dominant phylogenetic Class, represented by species from the genus Alkaliphilus. As observed with the mesophilic microcosms at pH 10, hydrogenotrophic methanogens dominated the Archaeal components of the consortia. The results presented in the following body of work suggest that the microbial colonisation of a GDF is likely within the construction and operational phases of the facility. Carbon dioxide is likely to be the predominant terminal electron acceptor within the facility and here methanogenesis has been observed up to a pH of 11.0. In each case, fermentation is likely to be as a result of alkaliphilic Clostridia, where methanogenesis appears to be limited to the hydrogenotrophic pathway at elevated pH. These findings are likely to inform safety assessments through both the application of rate data and gas generation predictions.

Investigation of rumen methanogens in New Zealand livestock

Abstract: Methane emitted by farmed ruminants contributes 30.3% to New Zealand’s anthropogenic greenhouse gas inventory. Methanogens living in the rumen produce methane from H2 and CO2 as a byproduct of feed fermentation. The use of vaccines and small molecule inhibitors against the methanogens are promising methods to reduce methane emissions from extensively-grazed ruminants in New Zealand. Knowledge of the methanogens present in New Zealand ruminants is an important first step for successful vaccine and inhibitor development to target all methanogens. In this study, the methanogen diversity of farmed ruminants (sheep [Ovis aries], cattle [Bos taurus] and red deer [Cervus elaphus]) was investigated using molecular ecological techniques. Ruminants fed different diets had largely similar rumen methanogen communities. The major methanogen groups identified were from the Methanobrevibacter ruminantium clade (Mbb. ruminantium and closely-related species), Methanobrevibacter gottschalkii clade (Mbb. gottschalkii and closely-related species), Methanosphaera spp., and the putative methanogens belonging to the group designated Rumen Cluster C. A total of 37.5 - 57% of 16S rRNA genes in the rumen of a group of cows originated from members of Rumen Cluster C. Chloroform treatment of cows increased the abundance of Rumen Cluster C to 82% - 93% of archaeal 16S rRNA genes. In parallel, a total of 22% of mcrA genes belonged to an unassigned group of archaea, and chloroform treatment increased the unassigned group of archaea to 92% of all mcrA genes. This suggested that Rumen Cluster C archaea contain the gene mcrA. No members of the Rumen Cluster C group have previously been cultured, and currently there is no reported rumen isolate of Methanosphaera spp. A strain of Methanosphaera sp. was isolated from a sheep rumen and initial characterization suggests that this may be a new species. Three enrichment cultures were obtained containing members of Rumen Cluster C as the only archaea. Initial studies of these enrichment cultures showed that these three isolates were from three different sub-groups of Rumen Cluster C and that they produced methane. The investigation of methanogen diversity in New Zealand farmed ruminants and isolation of previously uncultured rumen methanogens reported here in this thesis will significantly aid the development of methane reduction strategies for farmed ruminants in New Zealand.

Bacteria and methanogen community in the rumen fed different levels of grass-legume silages

Abstract: . Ridwan R, Rusmana I, Widyastuti Y, Wiryawan KG, Prasetya B, Sakamoto M, Ohkuma M. 2019. Bacteria and methanogen community in the rumen fed different levels of grass-legume silages. Biodiversitas 20: 1055-1062. This study aimed to investigate the effects of dietary grass-legume silages on the microbial community by using a culture-independent approach. Treatments consisted of R0: 50% Pennisetum purpureum and 50 % concentrate; R1: 20% P. purpureum, 50 % concentrate, and 30% grass-legumes silage; R2: 20% P. purpureum, 35 % concentrate, and 45% grass-legumes silage; and R3; 20% P. purpureum, 20 % concentrate, and 60% grass-legumes silage. The rumen fluid obtained from fistulated cattle was used for T-RFLP, 16S rDNA clone library, and qPCR analyses. The results indicated that bacterial diversity was dominated by Bacteroidetes, Firmicutes, and methanogen by Methanobacteriales, based on partial 16S rDNA sequences. The microbial communities were dominated by Prevotella brevis, P. ruminicola, Succiniclasticum ruminis, and Methanobrevibacter ruminantium, M. smithi, M. thueri, and M. millerae. The increasing silage diet in a rumen suppressed methanogenesis by reducing population distribution of Methanobacteriales, directly or indirectly, by reducing the diversity of bacterial populations. Generally, the increase silage in the diet changed the bacterial and methanogen community. Grass-legume silage diets of less than 45% are potential for ruminant diet to reduce methane production by a decrease of 4% in the relative distribution of methanogens in the rumen.