Inhibition of anaerobic digestion process: A review

The present application describes the complete 1.66-megabase pair genome sequence of an autotrophic archaeon, Methanococcus jannaschii, and its 58- and 16-kilobase pair extrachromosomal elements. Also described are 1738 predicted protein-coding genes.

https://science.sciencemag.org/content/sci/273/5278/1058.full.pdf

COMPLETE GENOME SEQUENCE OF THE METHANOGENIC ARCHAEON, $i(METHANOCOCCUS JANNASCHII)

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_7/b_fdi_57-58/010025232.pdf

Production, oxidation, emission and consumption of methane by soils: A review

Methane is the most abundant organic chemical in Earth's atmosphere, and its concentration is increasing with time, as a variety of independent measurements have shown. Photochemical reactions oxidize methane in the atmosphere; through these reactions, methane exerts strong influence over the chemistry of the troposphere and the stratosphere and many species including ozone, hydroxyl radicals, and carbon monoxide. Also, through its infrared absorption spectrum, methane is an important greenhouse gas in the climate system. We describe and enumerate key roles and reactions. Then we focus on two kinds of methane production: microbial and thermogenic. Microbial methanogenesis is described, and key organisms and substrates are identified along with their properties and habitats. Microbial methane oxidation limits the release of methane from certain methanogenic areas. Both aerobic and anaerobic oxidation are described here along with methods to measure rates of methane production and oxidation experimentally. Indicators of the origin of methane, including C and H isotopes, are reviewed. We identify and evaluate several constraints on the budget of atmospheric methane, its sources, sinks and residence time. From these constraints and other data on sources and sinks we construct a list of sources and sinks, identities, and sizes. The quasi-steady state (defined in the text) annual source (or sink) totals about 310(±60) × 1012 mol (500(±95) × 1012 g), but there are many remaining uncertainties in source and sink sizes and several types of data that could lead to stronger constraints and revised estimates in the future. It is particularly difficult to identify enough sources of radiocarbon-free methane.

/pdf/biogeochemical-aspects-of-atmospheric-methane-1j0pgr75la.pdf

Biogeochemical aspects of atmospheric methane

Pretreatment of lignocellulosic biomass for enhanced biogas production.

Previous studies of anaerobic biocorrosion have suggested that microbial sulfur and phosphorus products as well as cathodic hydrogen consumption may accelerate anaerobic metal oxidation. Methanogenic bacteria, which normally use molecular hydrogen (H(2)) and carbon dioxide (CO(2)) to produce methane (CH(4)) and which are major inhabitants of most anaerobic ecosystems, use either pure elemental iron (Fe(0)) or iron in mild steel as a source of electrons in the reduction of CO(2) to CH(4). These bacteria use Fe(0) oxidation for energy generation and growth. The mechanism of Fe(0) oxidation is cathodic depolarization, in which electrons from Fe(0) and H(+) from water produce H(2), which is then released for use by the methanogens; thermodynamic calculations show that significant Fe(0) oxidation will not occur in the absence of H(2) consumption by the methanogens. The data suggest that methanogens can be significant contributors to the corrosion of iron-containing materials in anaerobic environments.

https://science.sciencemag.org/content/sci/237/4814/509.full.pdf

Bacterial Methanogenesis and Growth from CO2 with Elemental Iron as the Sole Source of Electrons.

Several methanogenic bacteria were shown to produce ethane, ethylene, and acetylene when exposed to the halogenated hydrocarbons bromoethane, dibromo- or dichloroethane, and 1,2-dibromoethylene, respectively. They also produced ethylene when exposed to the coenzyme M analog and specific methanogenic inhibitor bromoethanesulfonic acid. The production of these gases from halogenated hydrocarbons has a variety of implications concerning microbial ecology, agriculture, and toxic waste treatment. All halogenated aliphatic compounds tested were inhibitory to methanogens. Methanococcus thermolithotrophicus, Methanococcus deltae, and Methanobacterium thermoautotrophicum ΔH and Marburg were completely inhibited by 7 μM 1,2-dibromoethane and, to various degrees, by 51 to 1,084 μM 1,2-dichloroethane, 1,2-dibromoethylene, 1,2-dichloroethylene, and trichloroethylene. In general, the brominated compounds were more inhibitory. The two Methanococcus species were fully inhibited by 1 μM bromoethanesulfonic acid, whereas both Methanobacterium strains were only partly inhibited by 2,124 μM. Coenzyme M protected cells from bromoethanesulfonic acid but not from any of the other inhibitors.

Production of Ethane, Ethylene, and Acetylene from Halogenated Hydrocarbons by Methanogenic Bacteria

A variety of sulfur-containing compounds were investigated for use as medium reductants and sulfur sources for growth of four methanogenic bacteria. Sulfide (1 to 2 mM) served all methanogens investigated well. Methanococcus thermolithotrophicus and Methanobacterium thermoautotrophicum Marburg and delta H grew well with S0, SO3(2-), or thiosulfate as the sole sulfur source. Only Methanococcus thermolithotrophicus was able to grow with SO4(2-) as the sole sulfur source. 2-Mercaptoethanol at 20 mM was greatly inhibitory to growth of Methanococcus thermolithotrophicus on SO4(2-) or SO2(2-) and Methanobacterium thermoautotrophicum Marburg on SO3(2-) but not to growth of strain delta H on SO3(2-). Sulfite was metabolized during growth by Methanococcus thermolithotrophicus. Sulfide was produced in cultures of Methanococcus thermolithotrophicus growing on SO4(2-), SO3(2-), thiosulfate, and S0. Methanobacterium thermoautotrophicum Marburg was successfully grown in a 10-liter fermentor with S0, SO3(2-), or thiosulfate as the sole sulfur source.

Assimilatory reduction of sulfate and sulfite by methanogenic bacteria.

Methanogenic bacteria are known to use NH+4 as a nitrogen source for growth1. Previous work with an impure methanogenic culture suggested that a methanogen might fix atmospheric dinitrogen as a nitrogen source2, but no further work on this phenomenon has been documented. We have now examined the use of N2 by Methanococcus thermolithotrophicus and find that the organism can grow well, with multiple transfers, in medium having N2 as the source of nitrogen. Control cultures without N2 and containing less than 0.1 mM NH+4 do not grow. Growth yields with N2 are on the average one-third those with NH+4, suggesting that, as in other nitrogen-fixing organisms, this bacterium requires a large amount of ATP for the reduction to occur. After growing in NH+4-containing medium, a long lag is observed before growth begins with N2 as the nitrogen source; the NH+4 levels must be very low for growth to begin. Cells grown in N2-fixing conditions reduce acetylene to ethylene. The discovery of a nitrogen-fixing archaebacterium has important implications for studies on the evolution of nitrogenase, and the fact that M. thermolithotrophicus nitrogenase is active at 64 °C suggests that a novel enzyme is involved.

Dinitrogen fixation by a thermophilic methanogenic bacterium

Twelve vaginal samples were collected from separate patients, processed anaerobically, and added to methanogenic enrichment medium. Methanogenic activity was detected in two samples, both of which were from patients with bacterial vaginosis. None of the samples from healthy patients yielded positive methanogen cultures. One sample from a patient with bacterial vaginosis did not show any detectable methanogenic activity. Two methanogen isolates were obtained from one of the methanogen-positive samples, and both were identified as Methanobrevibacter smithii on the basis of morphological, cultural, and immunological features.

Negash Belay

Papers

Bacterial Methanogenesis and Growth from CO2 with Elemental Iron as the Sole Source of Electrons.

Production of Ethane, Ethylene, and Acetylene from Halogenated Hydrocarbons by Methanogenic Bacteria

Assimilatory reduction of sulfate and sulfite by methanogenic bacteria.

Dinitrogen fixation by a thermophilic methanogenic bacterium

Methanogenic bacteria in human vaginal samples.