Hydrogenotrophic Methanogenesis Under Alkaline Conditions

A cement-based geological disposal facility (GDF) is one potential option for the disposal of intermediate level radioactive wastes. The presence of both organic and metallic materials within a GDF provides the opportunity for both acetoclastic and hydrogenotrophic methanogenesis. However, for these processes to proceed, they need to adapt to the alkaline environment generated by the cementitious materials employed in backfilling and construction. Within the present study, a range of alkaline and neutral pH sediments were investigated to determine the upper pH limit and the preferred route of methane generation. In all cases, the acetoclastic route did not proceed above pH 9.0, and the hydrogenotrophic route dominated methane generation under alkaline conditions. In some alkaline sediments, acetate metabolism was coupled to hydrogenotrophic methanogenesis via syntrophic acetate oxidation, which was confirmed through inhibition studies employing fluoromethane. The absence of acetoclastic methanogenesis at alkaline pH values (>pH 9.0) is attributed to the dominance of the acetate anion over the uncharged, undissociated acid. Under these conditions, acetoclastic methanogens require an active transport system to access their substrate. The data indicate that hydrogenotrophic methanogenesis is the dominant methanogenic pathway under alkaline conditions (>pH 9.0).

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Lignin intermediates lead to phenyl acid formation and microbial community shifts in meso- and thermophilic batch reactors

Biotechnology for Biofuels ◽

10.1186/s13068-020-01855-0 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Eva Maria Prem ◽

Mira Mutschlechner ◽

Blaz Stres ◽

Paul Illmer ◽

Andreas Otto Wagner

Keyword(s):

Microbial Community ◽

Aromatic Compounds ◽

Acid Formation ◽

Lignocellulose Degradation ◽

Batch Reactors ◽

Acetate Oxidation ◽

Hydrogenotrophic Methanogenesis ◽

Acetoclastic Methanogenesis ◽

Community Shifts ◽

Syntrophic Acetate Oxidation

Abstract Background Lignin intermediates resulting from lignocellulose degradation have been suspected to hinder anaerobic mineralisation of organic materials to biogas. Phenyl acids like phenylacetate (PAA) are early detectable intermediates during anaerobic digestion (AD) of aromatic compounds. Studying the phenyl acid formation dynamics and concomitant microbial community shifts can help to understand the microbial interdependencies during AD of aromatic compounds and may be beneficial to counteract disturbances. Results The length of the aliphatic side chain and chemical structure of the benzene side group(s) had an influence on the methanogenic system. PAA, phenylpropionate (PPA), and phenylbutyrate (PBA) accumulations showed that the respective lignin intermediate was degraded but that there were metabolic restrictions as the phenyl acids were not effectively processed. Metagenomic analyses confirmed that mesophilic genera like Fastidiosipila or Syntrophomonas and thermophilic genera like Lactobacillus, Bacillus, Geobacillus, and Tissierella are associated with phenyl acid formation. Acetoclastic methanogenesis was prevalent in mesophilic samples at low and medium overload conditions, whereas Methanoculleus spp. dominated at high overload conditions when methane production was restricted. In medium carbon load reactors under thermophilic conditions, syntrophic acetate oxidation (SAO)-induced hydrogenotrophic methanogenesis was the most important process despite the fact that acetoclastic methanogenesis would thermodynamically be more favourable. As acetoclastic methanogens were restricted at medium and high overload conditions, syntrophic acetate oxidising bacteria and their hydrogenotrophic partners could step in for acetate consumption. Conclusions PAA, PPA, and PBA were early indicators for upcoming process failures. Acetoclastic methanogens were one of the first microorganisms to be impaired by aromatic compounds, and shifts to syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis occurred in thermophilic reactors. Previously assumed associations of specific meso- and thermophilic genera with anaerobic phenyl acid formation could be confirmed.

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Effect of ammonia on methane production pathways and reaction rates in acetate-fed biogas processes

Water Science & Technology ◽

10.2166/wst.2017.032 ◽

2017 ◽

Vol 75 (8) ◽

pp. 1839-1848 ◽

Cited By ~ 14

Author(s):

L. P. Hao ◽

L. Mazéas ◽

F. Lü ◽

J. Grossin-Debattista ◽

P. J. He ◽

...

Keyword(s):

Methane Production ◽

Reaction Rates ◽

Ammonium Nitrogen ◽

Significant Inhibition ◽

Lag Phase ◽

Hydrogenotrophic Methanogenesis ◽

Thermophilic Conditions ◽

Acetoclastic Methanogenesis ◽

Syntrophic Acetate Oxidation ◽

Total Ammonium

In order to understand the correlation between ammonia and methanogenesis metabolism, methane production pathways and their specific rates were studied at total ammonium nitrogen (TAN) concentrations of 0.14–9 g/L in three methanogenic sludges fed with acetate, at both mesophilic and thermophilic conditions. Results showed that high levels of TAN had significant inhibition on methanogenesis; this could, however, be recovered via syntrophic acetate oxidation (SAO) coupled with Hydrogenotrophic Methanogenesis (HM) performed by acetate oxidizing syntrophs or through Acetoclastic Methanogenesis (AM) catalyzed by Methanosarcinaceae, after a long lag phase >50 d. Free ammonia (NH3) was the active component for this inhibition, of which 200 mg/L is suggested as the threshold for the pathway shift from AM to SAO-HM. Methane production rate via SAO-HM at TAN of 7–9 g/L was about 5–9-fold lower than that of AM at TAN of 0.14 g/L, which was also lower than the rate of AM pathway recovered at TAN of 7 g/L in the incubations with a French mesophilic inoculum. Thermophilic condition favored the establishment of the SAO-catalyzing microbial community, as indicated by the higher reaction rate and shorter lag phase. The operational strategy is thus suggested to be adjusted when NH3 exceeds 200 mg/L.

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Effect of Sub-Stoichiometric Fe(III) Amounts on LCFA Degradation by Methanogenic Communities

Microorganisms ◽

10.3390/microorganisms8091375 ◽

2020 ◽

Vol 8 (9) ◽

pp. 1375

Author(s):

Ana J. Cavaleiro ◽

Ana P. Guedes ◽

Sérgio A. Silva ◽

Ana L. Arantes ◽

João C. Sequeira ◽

...

Keyword(s):

Iron Reduction ◽

Anaerobic Bacteria ◽

Granular Sludge ◽

Microbial Interactions ◽

Methanogenic Activity ◽

Iron Reducing Bacteria ◽

Hydrogenotrophic Methanogenesis ◽

Degrading Bacteria ◽

Acetoclastic Methanogenesis ◽

Reducing Bacteria

Long-chain fatty acids (LCFA) are common contaminants in municipal and industrial wastewater that can be converted anaerobically to methane. A low hydrogen partial pressure is required for LCFA degradation by anaerobic bacteria, requiring the establishment of syntrophic relationships with hydrogenotrophic methanogens. However, high LCFA loads can inhibit methanogens, hindering biodegradation. Because it has been suggested that anaerobic degradation of these compounds may be enhanced by the presence of alternative electron acceptors, such as iron, we investigated the effect of sub-stoichiometric amounts of Fe(III) on oleate (C18:1 LCFA) degradation by suspended and granular methanogenic sludge. Fe(III) accelerated oleate biodegradation and hydrogenotrophic methanogenesis in the assays with suspended sludge, with H2-consuming methanogens coexisting with iron-reducing bacteria. On the other hand, acetoclastic methanogenesis was delayed by Fe(III). These effects were less evident with granular sludge, possibly due to its higher initial methanogenic activity relative to suspended sludge. Enrichments with close-to-stoichiometric amounts of Fe(III) resulted in a microbial community mainly composed of Geobacter, Syntrophomonas, and Methanobacterium genera, with relative abundances of 83–89%, 3–6%, and 0.2–10%, respectively. In these enrichments, oleate was biodegraded to acetate and coupled to iron-reduction and methane production, revealing novel microbial interactions between syntrophic LCFA-degrading bacteria, iron-reducing bacteria, and methanogens.

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Biological Self-Healing of Cement Paste and Mortar by Non-Ureolytic Bacteria Encapsulated in Alginate Hydrogel Capsules

Materials ◽

10.3390/ma13173711 ◽

2020 ◽

Vol 13 (17) ◽

pp. 3711

Author(s):

Mohammad Fahimizadeh ◽

Ayesha Diane Abeyratne ◽

Lee Sui Mae ◽

R. K. Raman Singh ◽

Pooria Pasbakhsh

Keyword(s):

Cement Paste ◽

Healing Process ◽

Cementitious Materials ◽

The Self ◽

Self Healing ◽

Alkaline Conditions ◽

Healing Agent ◽

Encapsulated Bacteria ◽

The Right

Crack formation in concrete is one of the main reasons for concrete degradation. Calcium alginate capsules containing biological self-healing agents for cementitious materials were studied for the self-healing of cement paste and mortars through in vitro characterizations such as healing agent survivability and retention, material stability, and biomineralization, followed by in situ self-healing observation in pre-cracked cement paste and mortar specimens. Our results showed that bacterial spores fully survived the encapsulation process and would not leach out during cement mixing. Encapsulated bacteria precipitated CaCO3 when exposed to water, oxygen, and calcium under alkaline conditions by releasing CO32− ions into the cement environment. Capsule rupture is not required for the initiation of the healing process, but exposure to the right conditions are. After 56 days of wet–dry cycles, the capsules resulted in flexural strength regain as high as 39.6% for the cement mortar and 32.5% for the cement paste specimens. Full crack closure was observed at 28 days for cement mortars with the healing agents. The self-healing system acted as a biological CO32− pump that can keep the bio-agents retained, protected, and active for up to 56 days of wet-dry incubation. This promising self-healing strategy requires further research and optimization.

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Effect of Temperature on Anaerobic Ethanol Oxidation and Methanogenesis in Acidic Peat from a Northern Wetland

Applied and Environmental Microbiology ◽

10.1128/aem.71.12.8191-8200.2005 ◽

2005 ◽

Vol 71 (12) ◽

pp. 8191-8200 ◽

Cited By ~ 99

Author(s):

Martina Metje ◽

Peter Frenzel

Keyword(s):

Volatile Fatty Acids ◽

Archaeal Community ◽

Dry Weight ◽

Effect Of Temperature ◽

Rrna Gene ◽

Polymorphism Analysis ◽

Optimum Temperature ◽

Hydrogenotrophic Methanogenesis ◽

Acetoclastic Methanogenesis ◽

Fe Reduction

ABSTRACT The effects of temperature on rates and pathways of CH4 production and on the abundance and structure of the archaeal community were investigated in acidic peat from a mire in northern Scandinavia (68°N). We monitored the production of CH4 and CO2 over time and measured the turnover of Fe(II), ethanol, and organic acids. All experiments were performed with and without specific inhibitors (2-bromoethanesulfonate [BES] for methanogenesis and CH3F for acetoclastic methanogenesis). The optimum temperature for methanogenesis was 25°C (2.3 μmol CH4 · g [dry weight]−1 · day−1), but the activity was relatively high even at 4°C (0.25 μmol CH4 · g [dry weight]−1 · day−1). The theoretical lower limit for methanogenesis was calculated to be at −5°C. The optimum temperature for growth as revealed by real-time PCR was 25°C for both archaea and bacteria. The population structure of archaea was studied by terminal restriction fragment length polymorphism analysis and remained constant over a wide temperature range. Hydrogenotrophic methanogenesis accounted for about 80% of the total methanogenesis. Most 16S rRNA gene sequences that were affiliated with methanogens and all McrA sequences clustered with the exclusively hydrogenotrophic order Methanobacteriales, correlating with the prevalence of hydrogenotrophic methanogenesis. Fe reduction occurred parallel to methanogenesis and was inhibited by BES, suggesting that methanogens were involved in Fe reduction. Based upon the observed balance of substrates and thermodynamic calculations, we concluded that the ethanol pool was oxidized to acetate by the following two processes: syntrophic oxidation with methanogenesis (i) as an H2 sink and (ii) as a reductant for Fe(III). Acetate accumulated, but a considerable fraction was converted to butyrate, making volatile fatty acids important end products of anaerobic metabolism.

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Gas Transportation in Saturated Cementitious Materials

MRS Proceedings ◽

10.1557/proc-353-913 ◽

1994 ◽

Vol 353 ◽

Author(s):

K. Iriya ◽

M. Hironaga ◽

M. Kawanishi

Keyword(s):

Transport Mechanism ◽

Gas Transport ◽

Water Saturation ◽

Gas Permeability ◽

Pressure Rise ◽

Cementitious Materials ◽

Threshold Pressure ◽

Structural Walls ◽

Methane Generation ◽

Engineered Barrier

AbstractRadioactive waste repositories are constructed underground below ground water level. Main engineered barrier of the repository consists of structural walls, backfill mortar, and consolidated wastes. Cementitious materials are mainly adopted for the engineered barrier. Gas (hydrogen or methane) generation due to corrosion and microbial degradation is predicted, since the waste consists of metals like steel and organic material. It is important issue to define gas transport mechanism in cementitious materials in order to assess the gas release influence on the engineered barrier and pressure rise in the repository. Although cementitious materials have enough permeability to transport gas in dry condition, it is expected to be impermeable or so in saturated condition, in which repository is placed. In this paper, water and gas permeability both in dry and saturated conditions are investigated. The pressure in the vault, and gas transport mechanism is predicted. Certain threshold pressure exists, and it can be recognized that gas permeability is dependent on water saturation degree at a pressure greater than the threshold pressure. Loading pressure of 0.7 MN / m2 is needed for the flow of gas in saturated concrete. Intrinsic gas permeability of 6.5 × 10−19 m2 is obtained, which is very small value to keep the low pressure inside the vault. Consequently, it is predicted that gas cannot be transported through the intact concrete, however, it can be transported through defective zone which is developed during construction, and so on.

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Stable carbon isotope discrimination in rice field soil during acetate turnover by syntrophic acetate oxidation or acetoclastic methanogenesis

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2010.12.019 ◽

2011 ◽

Vol 75 (6) ◽

pp. 1531-1539 ◽

Cited By ~ 44

Author(s):

Ralf Conrad ◽

Melanie Klose

Keyword(s):

Carbon Isotope ◽

Rice Field ◽

Carbon Isotope Discrimination ◽

Stable Carbon Isotope ◽

Field Soil ◽

Stable Carbon ◽

Acetate Oxidation ◽

Rice Field Soil ◽

Acetoclastic Methanogenesis ◽

Syntrophic Acetate Oxidation

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Syntrophic acetate oxidation replaces acetoclastic methanogenesis during thermophilic digestion of biowaste

Microbiome ◽

10.1186/s40168-020-00862-5 ◽

2020 ◽

Vol 8 (1) ◽

Cited By ~ 1

Author(s):

Stefan Dyksma ◽

Lukas Jansen ◽

Claudia Gallert

Keyword(s):

Anaerobic Digestion ◽

Amplicon Sequencing ◽

Metabolic Reconstruction ◽

Rrna Gene ◽

Wastewater Management ◽

Acetate Oxidation ◽

Mineralization Of Organic Matter ◽

Acetoclastic Methanogenesis ◽

Syntrophic Acetate Oxidation ◽

Production Knowledge

Abstract Background Anaerobic digestion (AD) is a globally important technology for effective waste and wastewater management. In AD, microorganisms interact in a complex food web for the production of biogas. Here, acetoclastic methanogens and syntrophic acetate-oxidizing bacteria (SAOB) compete for acetate, a major intermediate in the mineralization of organic matter. Although evidence is emerging that syntrophic acetate oxidation is an important pathway for methane production, knowledge about the SAOB is still very limited. Results A metabolic reconstruction of metagenome-assembled genomes (MAGs) from a thermophilic solid state biowaste digester covered the basic functions of the biogas microbial community. Firmicutes was the most abundant phylum in the metagenome (53%) harboring species that take place in various functions ranging from the hydrolysis of polymers to syntrophic acetate oxidation. The Wood-Ljungdahl pathway for syntrophic acetate oxidation and corresponding genes for energy conservation were identified in a Dethiobacteraceae MAG that is phylogenetically related to known SAOB. 16S rRNA gene amplicon sequencing and enrichment cultivation consistently identified the uncultured Dethiobacteraceae together with Syntrophaceticus, Tepidanaerobacter, and unclassified Clostridia as members of a potential acetate-oxidizing core community in nine full-scare digesters, whereas acetoclastic methanogens were barely detected. Conclusions Results presented here provide new insights into a remarkable anaerobic digestion ecosystem where acetate catabolism is mainly realized by Bacteria. Metagenomics and enrichment cultivation revealed a core community of diverse and novel uncultured acetate-oxidizing bacteria and point to a particular niche for them in dry fermentation of biowaste. Their genomic repertoire suggests metabolic plasticity besides the potential for syntrophic acetate oxidation.

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