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Methanogen
About: Methanogen is a research topic. Over the lifetime, 1146 publications have been published within this topic receiving 48254 citations.
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TL;DR: The results indicated that 16S rRNA levels of Methanomicrobiales and Methanosaetaceae in adhering sludge were higher than in deposited sludge, and they all contributed to the efficient performance of the fixed-bed reactor at low operating temperatures.
77 citations
TL;DR: In this paper, the authors identify common genes that define a methanogen, while gene differences are providing an insight into adaptations that allow methanogens survival and persistence under different environmental conditions.
Abstract: Reducing ruminant methane emissions is an important objective for ensuring the sustainability of ruminant-based agriculture. Methane is formed in the rumen by methanogens (part of the domain Archaea), mainly from H2 and CO2. Methanogens from a wide range of habitats are being genome-sequenced to gain a better understanding of their biology and, in particular, to identify targets for inhibition technologies for gut-associated methanogens. Genome comparisons are identifying common genes that define a methanogen, while gene differences are providing an insight into adaptations that allow methanogen survival and persistence under different environmental conditions. Within the rumen microbial food web, methanogens perform the beneficial task of removing H2, which allows reduced cofactors to be reoxidised and recycled, thereby enhancing the breakdown and fermentation of plant material. Therefore, rumen methane mitigation strategies need to consider alternative routes of H2 utilisation in the absence (or decreased levels) of methanogenesis to maintain rumen function. Two main alternatives are possible: enhancing rumen microorganisms that carry out reductive acetogenesis (combining CO2 and H2 to form acetate) or promotion of organisms that consume reducing equivalents during the conversion of metabolic intermediates (malate, fumarate and crotonate) into propionate and butyrate. A better understanding of the role and scale of methane oxidation in the rumen may also lead to future options for methane mitigation.
77 citations
TL;DR: An obligately anaerobic thermophilic sporeforming sulfate-reducing bacterium, named strain CAMZ, was isolated from a benzoate enrichment from a 58°C thermophilicity bioreactor as discussed by the authors.
Abstract: An obligately anaerobic thermophilic sporeforming sulfate-reducing bacterium, named strain CAMZ, was isolated from a benzoate enrichment from a 58°C thermophilic anaerobic bioreactor. The cells of strain CAMZ were 0.7 μm by 2–5 μm rods with pointed ends, forming single cells or pairs. Spores were central, spherical, and caused swelling of the cells. The Gram stain was negative. Electron donors used included lactate, pyruvate, acetate and other short chain fatty acids, short chain alcohols, alanine, and H2/CO2. Lactate and pyruvate were oxidized completely to CO2 with sulfate as electron acceptor. Sulfate was required for growth on H2/CO2, and both acetate and sulfide were produced from H2/CO2-sulfate. Sulfate, thiosulfate, or elemental sulfur served as electron acceptors with lactate as the donor while sulfite, nitrate, nitrite, betaine, or a hydrogenotrophic methanogen did not. The optimum temperature for growth of strain CAMZ was 55–60°C and the optimum pH value was 6.5. The specific activities of carbon monoxide dehydrogenase of cells of strain CAMZ grown on lactate, H2/CO2, or acetate with sulfate were 7.2, 18.1, and 30.8 μmol methyl viologen reduced min−1 [mg protein]−1, respectively, indicating the presence of the CO/Acetyl-CoA pathway in this organism. The mol%-G+C of strain CAMZ's DNA was 49.7. The new species name Desulfotomaculum thermoacetoxidans is proposed for strain CAMZ.
76 citations
TL;DR: This gas stream treatment process improves the quality and caloric value of the biogas and increases the methane content through the use of a chemo-autotrophic methanogen, uncoupled methanogenesis techniques and hollow fiber membranes.
Abstract: Off-gas from anaerobic digestion and landfills has significant potential as an alternative energy source. Current technologies to purify off-gas and increase its caloric value have been primarily limited to physicochemical methods. An alternative biological method has been proposed that increases the methane content. Through the use of a chemo-autotrophic methanogen (Methanobacterium thermoautotrophicum), uncoupled methanogenesis techniques and hollow fiber membranes, carbon dioxide is converted to methane and hydrogen sulfide is effectively removed from biological off-gases. This gas stream treatment process improves the quality and caloric value of the biogas. A continuous culture bench-scale system that utilizes hollow fiber membranes was employed to study the process. The gas-phase methane concentrations were found to increase from 60% to 96%.
75 citations
TL;DR: Methanogenesis per ciliate protozoan and most probable numbers (MPN) of methanogens per c affiliate were measured and observed to be affected by feeding and indicated that apparent methane production by ciliates depended primarily on the number of meethanogens associated with them.
75 citations