Showing papers on "Methanogenesis published in 2018"
TL;DR: A critical summary of microbial characteristics was provided to obtain connects of microbial community structure with operational conditions at various states of AD, such as mesophilic and thermophilic, wet and dry, success and failure, pretreated or not, lab-scale and full-scale.
328 citations
TL;DR: This review summarizes the biochemical and metabolic background of methanogenesis as well as the latest technical applications of meethanogens to give a sufficient overview over the topic to both, biologists and engineers handling biological or bioelectrochemical meethanogenesis.
Abstract: Since fossil sources for fuel and platform chemicals will become limited in the near future, it is important to develop new concepts for energy supply and production of basic reagents for chemical industry. One alternative to crude oil and fossil natural gas could be the biological conversion of CO2 or small organic molecules to methane via methanogenic archaea. This process has been known from biogas plants, but recently, new insights into the methanogenic metabolism, technical optimizations and new technology combinations were gained, which would allow moving beyond the mere conversion of biomass. In biogas plants, steps have been undertaken to increase yield and purity of the biogas, such as addition of hydrogen or metal granulate. Furthermore, the integration of electrodes led to the development of microbial electrosynthesis (MES). The idea behind this technique is to use CO2 and electrical power to generate methane via the microbial metabolism. This review summarizes the biochemical and metabolic background of methanogenesis as well as the latest technical applications of methanogens. As a result, it shall give a sufficient overview over the topic to both, biologists and engineers handling biological or bioelectrochemical methanogenesis.
275 citations
TL;DR: Ferroferric oxide was dosed in an anaerobic sequencing batch reactor fed with tryptone-based synthetic wastewater and enhanced the maximum methane production rate by 78.3% in a reaction cycle but also improved methane production when hydrogen/carbon dioxide or acetate was used as the substrate.
242 citations
TL;DR: In this article, the authors report the enrichment and characterisation of a novel archaeon in a laboratory-scale bioreactor fed with Fe(III) oxide (ferrihydrite) and methane.
Abstract: Microbially mediated anaerobic oxidation of methane (AOM) is a key process in the regulation of methane emissions to the atmosphere. Iron can serve as an electron acceptor for AOM, and it has been suggested that Fe(III)-dependent AOM potentially comprises a major global methane sink. Although it has been proposed that anaerobic methanotrophic (ANME) archaea can facilitate this process, their active metabolic pathways have not been confirmed. Here we report the enrichment and characterisation of a novel archaeon in a laboratory-scale bioreactor fed with Fe(III) oxide (ferrihydrite) and methane. Long-term performance data, in conjunction with the 13C- and 57Fe-labelling batch experiments, demonstrated that AOM was coupled to Fe(III) reduction to Fe(II) in this bioreactor. Metagenomic analysis showed that this archaeon belongs to a novel genus within family Candidatus Methanoperedenaceae, and possesses genes encoding the “reverse methanogenesis” pathway, as well as multi-heme c-type cytochromes which are hypothesised to facilitate dissimilatory Fe(III) reduction. Metatranscriptomic analysis revealed upregulation of these genes, supporting that this archaeon can independently mediate AOM using Fe(III) as the terminal electron acceptor. We propose the name Candidatus “Methanoperedens ferrireducens” for this microorganism. The potential role of “M. ferrireducens” in linking the carbon and iron cycles in environments rich in methane and iron should be investigated in future research.
231 citations
TL;DR: A deeper understanding of the mechanism in the bioconversion of lignocellulosic biomass during anaerobic digestion is provided and it is shown that hemicellulose was hydrolysed more quickly than cellulose, while lignin was very difficult to be digested.
225 citations
TL;DR: Analysis of stable carbon isotopes and determination of key enzymes showed that IHT could be partially substituted by enhanced DIET, and acetate-dependent methanogenesis was improved after the blockage of electron transfer was scavenged, proving that direct interspecies electron transfer (DIET) was enhanced by magnetite.
Abstract: At present, high-solids anaerobic digestion of sewage sludge has drawn great attention due to the superiority of its small land area footprint and low energy consumption. However, a high organic loading rate may cause acids accumulation and ammonia inhibition, thus leading to an inhibited pseudo-steady state in which electron transfer through interspecies hydrogen transfer (IHT) between acetogens and methanogens is blocked. In this study, adding 50 mg/g TS (total solid) magnetite clearly reduced the accumulation of short-chain fatty acids and accelerated methane production by 26.6%. As demonstrated, the individual processes of anaerobic digestion could not be improved by magnetite when methanogenesis was interrupted. Analyzing stable carbon isotopes and investigating the methanogenesis pathways using acetate and H2/CO2 as substrates together proved that direct interspecies electron transfer (DIET) was enhanced by magnetite. Metatranscriptomic analysis and determination of key enzymes showed that IHT could...
180 citations
TL;DR: When adding Fe3O4 and ZVI simultaneously into an anaerobic digester, the abundance of hydrogenotrophic methanogens decreased drastically compared to ZVI-added digester and Fe-free digesters, which implied that the potential DIET between Syntrophomonas and Methanosaeta was likely a crucial reason for accelerating an aerobic digestion of waste sludge.
172 citations
TL;DR: RB and MB stimulate methanogenesis by facilitating direct interspecies electron transfer between methanogens and Geobacteraceae, and Quantitative polymerase chain reaction results demonstrated that electronic syntrophy did exist between meethanogenic and anaerobic bacteria.
Abstract: Biochar has the potential to influence methanogenesis which is a key component of global carbon cycling. However, the mechanisms governing biochar's influence on methanogenesis is not well understood, especially its effects on interspecies relationships between methanogens and anaerobic bacteria (e.g., Geobacteraceae). To understand how different types of biochar influence methanogenesis, biochars derived from rice straw (RB), wood chips (WB), and manure (MB) were added to the methanogenic enrichment culture system of a paddy soil. Compared to the nonbiochar control, RB and MB additions accelerated methanogenesis remarkably, showing 10.7 and 12.3-folds higher methane production rate, respectively; while WB had little effect on methanogenesis. Using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electrochemical methods, RB and MB also had higher redox-active properties or charging and discharging capacities than WB, and the functional groups, mainly quinones, on the biochar surface played an important role in facilitating methanogenesis. Quantitative polymerase chain reaction results demonstrated that electronic syntrophy did exist between methanogens and Geobacteraceae. RB and MB stimulate methanogenesis by facilitating direct interspecies electron transfer between methanogens and Geobacteraceae. Our findings contribute to a better understanding of the effects of biochars from different feedstocks on methanogenesis and provide new evidence to the mechanisms of stimulating methanogenesis via biochar.
151 citations
TL;DR: Red mud's role in methanogenesis showed that the multivalent cations from hematite effectively promoted the formation of large and compact aggregates, which might contribute to the rapid direct electron exchange during the DIET process.
150 citations
TL;DR: The MEC did not increase the methane yield over the theoretical value, but accelerated methane production and stabilization by bioelectrochemical reactions, based on results.
148 citations
TL;DR: Mechanism explorations revealed that the addition of cPAM significantly restrained the sludge solubilization, hydrolysis, acidogenesis, and methanogenesis processes, and it was found that ∼46% of cAPM was degraded in the anaerobic digestion, and the degradation products significantly affected methane production.
TL;DR: Results indicate that ZVI promoted anaerobic digestion of WAS through promoting hydrogenotrophic methanogenesis, increasing methane production by 70% and Fe3O4 competed with CH3▪S▪CoM for electrons and thus inhibited the methanogenic process.
TL;DR: Investigation of whether the addition of magnetite could help reactors treating MSW incineration leachate overcome limitations and promote efficient conversion of complex organic matter to methane showed that magnetite amendments improved chemical oxygen demand (COD) removal efficiencies and methane production rates.
TL;DR: It is reported that wild-type iron-iron (Fe-only) nitrogenase from the bacterium Rhodopseudomonas palustris can generate CH4 in a single step, which can consequently be used for growth by a CH4-utilizing Methylomonas strain.
Abstract: Methane (CH4) is a potent greenhouse gas that is released from fossil fuels and is also produced by microbial activity, with at least one billion tonnes of CH4 being formed and consumed by microorganisms in a single year
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. Complex methanogenesis pathways used by archaea are the main route for bioconversion of carbon dioxide (CO2) to CH4 in nature2–4. Here, we report that wild-type iron-iron (Fe-only) nitrogenase from the bacterium Rhodopseudomonas palustris reduces CO2 simultaneously with nitrogen gas (N2) and protons to yield CH4, ammonia (NH3) and hydrogen gas (H2) in a single enzymatic step. The amount of CH4 produced by purified Fe-only nitrogenase was low compared to its other products, but CH4 production by this enzyme in R. palustris was sufficient to support the growth of an obligate CH4-utilizing Methylomonas strain when the two microorganisms were grown in co-culture, with oxygen (O2) added at intervals. Other nitrogen-fixing bacteria that we tested also formed CH4 when expressing Fe-only nitrogenase, suggesting that this is a general property of this enzyme. The genomes of 9% of diverse nitrogen-fixing microorganisms from a range of environments encode Fe-only nitrogenase. Our data suggest that active Fe-only nitrogenase, present in diverse microorganisms, contributes CH4 that could shape microbial community interactions.
TL;DR: PF positively enriched the abundance of microorganisms responsible for WAS hydrolysis and SCFAs production, especially acetic acid-forming characteristic genera such as Petrimonas, Fusibacter and Acetoanaerobium.
TL;DR: It is found that degradation rates transition continuously from the sulfate to the methane zone, thereby demonstrating that terminal steps do not exert feedback control on upstream hydrolytic and fermentative processes, as previously suspected.
Abstract: The degradation of organic matter in the anoxic seabed proceeds through a complex microbial network in which the terminal steps are dominated by oxidation with sulfate or conversion into methane and CO2. The controls on pathway and rate of the degradation process in different geochemical zones remain elusive. Radiotracer techniques were used to perform measurements of sulfate reduction, methanogenesis, and acetate oxidation with unprecedented sensitivity throughout Holocene sediment columns from the Baltic Sea. We found that degradation rates transition continuously from the sulfate to the methane zone, thereby demonstrating that terminal steps do not exert feedback control on upstream hydrolytic and fermentative processes, as previously suspected. Acetate was a key intermediate for carbon mineralization in both zones. However, acetate was not directly converted into methane. Instead, an additional subterminal step converted acetate to CO2 and reducing equivalents, such as H2, which then fed autotrophic reduction of CO2 to methane.
TL;DR: The degradation of MOCs was improved by THP at different rates, in which improved degradation of proteins and hemicelluloses were the main factors contributing to the increase in volatile solids reduction, but no enhancement of final degradation extent of Mocs was observed.
TL;DR: The added biochar not only favors the anaerobic sludge granulation working as an inert core, but also facilitates the selective enrichment of potential direct interspecies electron transfer (DIET) partners such as Methanothrix and Geobacter spp.
TL;DR: It is found that methylation rates vary inherently among hgcAB+ methanogens but that several species are capable of MeHg production at rates that rival those of the better-know Hg-methylating sulfate- and iron-reducing bacteria.
Abstract: Methylmercury (MeHg) production was compared among nine cultured methanogenic archaea that contain hgcAB, a gene pair that codes for mercury (Hg) methylation. The methanogens tested produced MeHg at inherently different rates, even when normalized to growth rate and Hg availability. Eight of the nine tested were capable of MeHg production greater than that of spent- and uninoculated-medium controls during batch culture growth. Methanococcoides methylutens, an hgcAB+ strain with a fused gene pair, was unable to produce more MeHg than controls. Maximal conversion of Hg to MeHg through a full batch culture growth cycle for each species (except M. methylutens) ranged from 2 to >50% of the added Hg(II) or between 0.2 and 17 pmol of MeHg/mg of protein. Three of the species produced >10% MeHg. The ability to produce MeHg was confirmed in several hgcAB+ methanogens that had not previously been tested (Methanocella paludicola SANAE, Methanocorpusculum bavaricum, Methanofollis liminatans GKZPZ, and Methanosphaerula palustris E1-9c). Maximal methylation was observed at low sulfide concentrations (<100 μM) and in the presence of 0.5 to 5 mM cysteine. For M. hollandica, the addition of up to 5 mM cysteine enhanced MeHg production and cell growth in a concentration-dependent manner. As observed for bacterial Hg methylators, sulfide inhibited MeHg production. An initial evaluation of sulfide and thiol impacts on bioavailability showed methanogens responding to Hg complexation in the same way as do Deltaproteobacteria The mercury methylation rates of several methanogens rival those of the better-studied Hg-methylating sulfate- and iron-reducing DeltaproteobacteriaIMPORTANCEArchaea, specifically methanogenic organisms, play a role in mercury methylation in nature, but their global importance to MeHg production and the subsequent risk to ecosystems are not known. Methanogenesis has been linked to Hg methylation in several natural habitats where methylmercury production incurs risk to people and ecosystems, including rice paddies and permafrost. In this study, we confirm that most methanogens carrying the hgcAB gene pair are capable of Hg methylation. We found that methylation rates vary inherently among hgcAB+ methanogens but that several species are capable of MeHg production at rates that rival those of the better-know Hg-methylating sulfate- and iron-reducing bacteria. Methanogens may need to be considered equally with sulfate and iron reducers in evaluations of MeHg production in nature.
TL;DR: The results of this study demonstrate the feasibility of using glycerol as co-substrate to increase the H2 and CH4 production efficiency in a two-stage anaerobic co-digestion process, allowing simultaneous treatment of three residues and energy production.
TL;DR: The effects of ammonia on methane production, methanogenesis pathway, microbial community, and reactor performance were investigated in this article, where more than 20% of methane production loss was observed in mesophilic and thermophilic reactors when the ammonia level exceeded 2 and 5 1/g NH4+-N/L, respectively.
TL;DR: Support for methanogenesis predating the Archaean is found by analysing horizontal gene transfer events between methanogenic Archaea and Cyanobacteria, which show methanogens diverging within Euryarchaeota no later than 3.51 billion years ago.
Abstract: Microbial methanogenesis may have been a major component of Earth’s carbon cycle during the Archaean eon, generating a methane greenhouse that increased global temperatures enough for a liquid hydrosphere, despite the Sun’s lower luminosity at the time. Evaluation of potential solutions to the ‘faint young Sun’ hypothesis by determining the age of microbial methanogenesis has been limited by ambiguous geochemical evidence and the absence of a diagnostic fossil record. To overcome these challenges, we use a temporal constraint: a horizontal gene transfer event from within archaeal methanogens to the ancestor of Cyanobacteria, one of the few microbial clades with recognized crown-group fossils. Results of molecular clock analyses calibrated by this horizontal-gene-transfer-propagated constraint show methanogens diverging within Euryarchaeota no later than 3.51 billion years ago, with methanogenesis itself probably evolving earlier. This timing provides independent support for scenarios wherein microbial methane production was important in maintaining temperatures on the early Earth.
TL;DR: This study reported a novel and efficient approach to improve the anaerobic fermentation performance of waste activated sludge (WAS) by the indigenous iron activated persulfate (PS/Fe) treatment which remarkably enhanced the production of short-chain fatty acids (SCFAs) within shorter fermentation time.
TL;DR: The role of red mud in the improvement of methanogenesis during sludge anaerobic digestion was innovatively investigated and a novel perspective on the synergism between sludge and red mud for methane production is provided.
TL;DR: In this paper, different granular activated carbon (GAC) dosages of 0, 0.5, 5, 5 and 25 were supplemented into anaerobic digesters and the methanogenic degradation kinetics of acetate, propionate and butyrate were characterized, respectively.
TL;DR: Results indicate that regional pH variation in the microenvironment surrounding the electrode is an ecological niche enriched with Methanobacterium, which is a promising method for accelerating and stabilising bioenergy recovery in anaerobic processes.
TL;DR: Microbial community analysis showed that the addition of diclofenac could promote the relative abundance of VFAs (especially acetic acid) producers, which was well consistent with the results obtained.
TL;DR: The potential of ZVI addition to enhance AD of ammonia-rich animal manure was demonstrated, and fast growing and ammonia-tolerant hydrogenotrophic Methanoculleus species were enriched with ZVI, helping achieve a 54.2% higher CH4 yield relative to control.
TL;DR: It is suggested that magnetite-mediated direct interspecies electron transfer (DIET) between Geobacter and Methanosaeta species was likely a crucial reason to promote syntrophic metabolism of propionic acid and butyric acid, and further enhance final methanogenesis.
TL;DR: High-throughput sequencing showed that methane production may stem from the involvement of Methanosarcina for both treatments, suggesting that conductive carbon material can promote acetoclastic methanogenesis instead of CO2 reduction in a natural environment.