Topic
Methanogen
About: Methanogen is a research topic. Over the lifetime, 1146 publications have been published within this topic receiving 48254 citations.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: This study showed that four parallel reactors co-digesting manure and fish waste silage operated stably during a startup phase and may be useful for the operation of biogas plants degrading substrates with high concentrations of proteins.
Abstract: Biogas is a renewable energy carrier which is used for heat and power production or, in the form of purified methane, as a vehicle fuel. The formation of methane from organic materials is carried out by a mixed microbial community under anaerobic conditions. However, details about the microbes involved and their function are limited. In this study we compare the metagenomes of four parallel biogas reactors digesting a protein-rich substrate, relate microbiology to biogas performance, and observe differences in these reactors’ microbial communities compared to the original inoculum culture. The biogas process performance during the startup phase of four parallel continuous stirred tank reactors (designated R1, R2, R3, and R4) co-digesting fish waste and cow manure was studied. The microbial composition of the inoculum (day 0) and the four reactors at day 59 was studied and compared using 454 FLX Titanium pyrosequencing. In the inoculum and the reactor samples, the Bacteria Clostridium and Syntrophomonas were highly abundant, and the dominating methanogen was the hydrogenotrophic Methanoculleus. Syntrophic prokaryotes frequently found in biogas reactors with high concentrations of ammonium and volatile fatty acids were detected in all samples. The species Candidatus Cloacimonas acidaminovorans of the candidate phylum Cloacimonetes (WWE1) increased in all reactors and was the dominating bacterium at day 59. In particular, this bacterium showed a very high abundance in R1, which distinguished this reactor significantly from the other reactors in terms of microbial composition. Methane production and the reactor slurry characteristics were monitored in the digestion period. Generally all four reactors operated stably and showed rather similar characteristics. The average methane production in the reactors varied between 0.278 and 0.296 L gVS-1, with the lowest production in R1. This study showed that four parallel reactors co-digesting manure and fish waste silage operated stably during a startup phase. Several important Archaea and Bacteria degrading the protein-rich substrate were identified. In particular, microorganisms involved in syntrophic methane production seemed to be important. The detailed characterization of the microbial communities presented in this work may be useful for the operation of biogas plants degrading substrates with high concentrations of proteins.
138 citations
••
TL;DR: It is suggested that methanogens take longer than 4 weeks to adapt to dietary changes and call into question the validity of experimental results based upon a 2- to 4-week acclimatization period normally observed for bacteria.
Abstract: The objectives of this study were to formulate a vaccine based upon the different species/strains of methanogens present in sheep intended to be immunized and to determine if a targeted vaccine could be used to decrease the methane output of the sheep. Two 16S rRNA gene libraries were used to survey the methanogenic archaea in sheep prior to vaccination, and methanogens representing five phylotypes were found to account for >52% of the different species/strains of methanogens detected. A vaccine based on a mixture of these five methanogens was then formulated, and 32 sheep were vaccinated on days 0, 28, and 103 with either a control or the anti-methanogen vaccine. Enzyme-linked immunosorbent assay analysis revealed that each vaccination with the anti-methanogen formulation resulted in higher specific immunoglobulin G titers in plasma, saliva, and rumen fluid. Methane output levels corrected for dry-matter intake for the control and treatment groups were not significantly different, and real-time PCR data also indicated that methanogen numbers were not significantly different for the two groups after the second vaccination. However, clone library data indicated that methanogen diversity was significantly greater in sheep receiving the anti-methanogen vaccine and that the vaccine may have altered the composition of the methanogen population. A correlation between 16S rRNA gene sequence relatedness and cross-reactivity for the methanogens (R2 = 0.90) also exists, which suggests that a highly specific vaccine can be made to target specific strains of methanogens and that a more broad-spectrum approach is needed for success in the rumen. Our data also suggest that methanogens take longer than 4 weeks to adapt to dietary changes and call into question the validity of experimental results based upon a 2- to 4-week acclimatization period normally observed for bacteria.
138 citations
••
TL;DR: It was found that the sensitivity of the pure cultures was similar to that of the methanogens in the sludge, and the numbers of methanogenic bacteria were affected by the presence of propionate even at concentrations as low as 20 or 30 mM.
Abstract: The effect of propionate toxicity at different pH values (6.5, 7.0, and 8.0) on methanogen-enriched sludge. Methanobrevibacter smithii, and Methanospirillum hungatii was studied. Organisms were grown in Balch medium 3 in Hungate tubes, and toxicity was characterized by a decrease in production of methane and in bacterial numbers. Propionate inhibited bacterial growth and cumulative methane production at concentrations as low as 20 mM. In the absence of propionate, the methanogen-enriched sludge and M. smithii showed better cumulative methane production at pH 6.5 and 7.0 than at pH 8.0. However, in the presence of propionate, these organisms showed better cumulative methane production at pH 8.0. M. hungatii differed in its behavior; the best values of cumulative methane production for this organism occurred at pH 7.0. Bacterial numbers reflected the microbial response to the presence of propionate. The highest counts of methanogenic bacteria were observed at pH 6.5 and 8.0. The numbers of methanogens were affected by the presence of propionate even at concentrations as low as 20 or 30 mM; at propionate concentrations above 80 mM, the methanogen count was affected by at least 2 orders of magnitude. Upon comparison of the responses of the pure cultures and the methanogen-enriched sludge to increasing propionate concentrations, it was found that the sensitivity of the pure cultures was similar to that of the methanogens in the sludge.
137 citations
••
TL;DR: It is found that intermittent drainage did not affect the growth of rice plants but significantly reduced the rates of both methane production and emission, and the composition of methanogenic community remained stable under dry/wet cycles, whereas that of metabolically active methanogens strongly changed.
Abstract: Intermittent drainage can substantially reduce methane emission from rice fields, but the microbial mechanisms remain poorly understood. In the present study, we determined the rates of methane production and emission, the dynamics of ferric iron and sulfate, and the abundance of methanogen mcrA genes (encoding the alpha subunit of methyl coenzyme M reductase) and their transcripts in response to alternate dry/wet cycles in paddy field soil. We found that intermittent drainage did not affect the growth of rice plants but significantly reduced the rates of both methane production and emission. The dry/wet cycles also resulted in shifts of soil redox conditions, increasing the concentrations of ferric iron and sulfate in the soil. Quantitative PCR analysis revealed that both mcrA gene copies and mcrA transcripts significantly decreased after dry/wet alternation compared to continuous flooding. Correlation and regression analyses showed that the abundance of mcrA genes and transcripts positively correlated with methane production potential and soil water content and negatively correlated with the concentrations of ferric iron and sulfate in the soil. However, the transcription of mcrA genes was reduced to a greater extent than the abundance of mcrA genes, resulting in very low mcrA transcript/gene ratios after intermittent drainage. Furthermore, terminal restriction fragment length polymorphism analysis revealed that the composition of methanogenic community remained stable under dry/wet cycles, whereas that of metabolically active methanogens strongly changed. Collectively, our study demonstrated a stronger effect of intermittent drainage on the abundance of mcrA transcripts than of mcrA genes in rice field soil.
137 citations
••
TL;DR: Based on the phylogenetic and phenotypic analyses, the novel species Methanosaeta harundinacea sp.
Abstract: Two methanogenic strains, 8AcT and 6Ac, were isolated from an upflow anaerobic sludge blanket reactor treating beer-manufacture wastewater in Beijing, China. Cells of strains 8AcT and 6Ac were rod-shaped (0·8–1·0×3–5 μm) and non-motile, occurring singly or in pairs; however, at high cell density the cells were arranged in long chains within a common sheath. The two strains used acetate exclusively for growth and methane production. The specific growth rate of strain 8AcT was 0·030 h−1 when growing in acetate (20 mM) at 37 °C. The temperature range for growth was 25–45 °C, with the fastest growth at 34–37 °C. The pH range for growth and methane production was 6·5–9·0, with the fastest growth at pH 7·2–7·6. The G+C content of genomic DNA of strain 8AcT was 55·7 mol%. Phylogenetic analysis based on 16S rRNA gene sequence similarity showed that the novel strains clustered with Methanosaeta species; the 16S rRNA gene sequence similarities between strain 8AcT and Methanosaeta concilii DSM 3013 and ‘Methanosaeta thermophila’ DSM 6194 were 92·5 and 87·3 %, respectively. The sequence similarity levels of mcrA, the gene encoding the α-subunit of methyl-coenzyme M reductase, and of the deduced amino acids of mcrA, between strain 8AcT and Methanosaeta concilii DSM 3671T were 36 and 78·9 %, respectively. Based on the phylogenetic and phenotypic analyses, the novel species Methanosaeta harundinacea sp. nov. is proposed, with strain 8AcT (=JCM 13211T=CGMCC 1.5026T) as the type strain.
134 citations