Biogenesis of Methane

Mah, Robert A.; Ward, David M.; Baresi, Larry; Glass, Thomas L.

doi:10.1146/annurev.mi.31.100177.001521

Cited by 303 publications

(160 citation statements)

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“…This is exactly what the methanogens do, eventually converting the hydrogen and carbon dioxide passed to them into the relatively inert gas, methane. 4 This process, known as interspecies hydrogen transfer, results in the stepwise degradation of the organic material coming into the system and prevents buildup of low molecular weight products which are unf ermentable or which might inhibit metabolism at some point (5,7]. In these systems, the methanogens have filled a unique ecological niche in which there is a mutualistic relationship between the methanogens and non-methanogens.…”

Section: Ecology Of the Methanogensmentioning

confidence: 99%

“…Many of these systems depend upon acetotrophs and hydrogenotrophic methanogens to keep the partial 5 pressure of hydrogen and acetate concentration down to an acceptable level, thus keeping the pH up [7]. It has been shown that 6 most methanogens grow best when the pH is near neutrality or slightly alkaline.…”

Section: Ecology Of the Methanogensmentioning

confidence: 99%

“…This is not surprising, since methanopterin bears a structural resemblance to folic acid, which participates in other well known metabolic processes as tetrahydrofolate and other derivatives, Other compounds found with or associated with methanopterin and FAF may be artifacts caused by the breakdown of the unstable and easily oxidized FAF [24,26,31]. The structure of methanopterin is shown in and has long been identified as being involved with the binding of a methyl group with a subsequent demethylation yielding methane [5].…”

Section: Methanopterin and Fafmentioning

confidence: 99%

“…Environments where methanogens are found include fresh water, estuarine, and marine sediments, flooded soils, animal digestive systems, and anaerobic sludge digestors [5]. It has been estimated that approximately 70% of the trace methane in the earth's atmosphere is from methanogenic metabolism [6], This thesis will be a review of the currently known inf ormation about this unique group of organisms, and will include a description of a partial purification and characterization of an F 420 -dependent nicotinamide adenine dinucleotide phosphate (NADP) reductase from one of these organisms, Methanobrevibacter smithii strain DEl.…”

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confidence: 99%

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Partial purification and characterization of F₄₂₀-dependent NADP reductase from Methanobrevibacter smithii strain DE1

Sheridan¹

2000

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The F 420 -dependent NADP reductase of Methanobrevibacter smithii has been partially purified employing a combination of affinity chromatography with Blue Sepharose (Cl-6B) and molecular sieve chromatography with Sephacryl S-200, The enzyme, which requires reduced F 420 as an electron donor, has been purified over 145 fold with a recovery of 6%. A molecular weight of 120,00 for the native enzyme was determined by Sephacryl S-200 chromatography.A subunit molecular weight of 28,200 was determined by SDS-PAGE, indicating that the native enzyme is a tetramer. The optimal temperature for enzymatic activity was found to be 45°C, with a pH optimum of 7.5. The NADP reductase had an apparent Km of 42 ~M for reduced F 420 , and an apparent Km of 4lfM for NADP. The enzyme was stable in 0.05 M sodium phosphate buffer (plus 10 mM cysteine) at pH 7.0, when gassed with nitrogen or hydrogen and stored at 4°C. Thanks should also go to Mary Taylor for always being there to lend a hand or the benefit of her experience. Mary is also one of those special educators who always have time for their students.I must give special credit to Sanjay Khandekar, the Test Tube King, for painstakingly making sure the spectrophotometer tubes were never without a protective coat of rust, and for giving me se~eral useful sources for this thesis. Also, he's kind of funny. In systems where sulphur reduction to hydrogen sulfide is an important pathway, methanogenesis is retarded, suggesting that the two reactions are competit~ve [7].Methanogenic bacteria may be found in systems with widely varying conditions, cool to very hot, organically rich or poor, and high or low pressure. Some methanogens require only hydrogen and carbon dioxide, while others require additional nutrients. Those ecosystems containing mostly carbon dioxide of geochemical origin are known as the chemolithotrophic systems. They occur primarily in thermal springs and lakes where volcanic intrusion of some kind is present [7]. The methanogens present in these environments are often quite hardy, thermophilic, and obviously are efficient at obtaining energy and cell mass from compounds which are unmetabolizable to other organisms.The other type of methanogenic ecosystem contains large to moderate amounts of organic monomers and polymers of biogenic and/or synthetic origin. This type of environment occurs in the digestive tracts of various animals, especially in the ruminants, and in places where material is being biodegraded anaerobically, such as swamps, bogs, sediments, water-saturated soils, sewage sludge, liquid waste digestors, biogas installations, garbage dumps, and landfills. It is in some of these environments that the presence of methanogens is important, both as the final link in the anaerobic food chain, and as scavengers which help control the pH and partial pressure of hydrogen, factors which are extremely important for the complete dissimilation of organic material in anaerobic environments.In these systems, which are almost always mixed cultures of several methanogen...

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Section: Ecology Of the Methanogensmentioning

confidence: 99%

Section: Ecology Of the Methanogensmentioning

confidence: 99%

Section: Methanopterin and Fafmentioning

confidence: 99%

mentioning

confidence: 99%

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Partial purification and characterization of F₄₂₀-dependent NADP reductase from Methanobrevibacter smithii strain DE1

Sheridan¹

2000

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“…Figure 2 depicts the fate of complex organic polymers such as proteins, carbohydrates and lipids in anaerobic environments (11). The fermentation of these polymers takes place in three consecutive steps.…”

Section: Significance Of Methanogens In Anaerobic Environmentmentioning

confidence: 99%

Purification and characterization of fumarate reductase from Methanobacterium thermoautotrophicum

Khandekar

2000

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Linearized Kinetic Models for the Simulation of the Mesophilic Anaerobic Digestion of Pre-hydrolyzed Woody Wastes

Converti

Borghi

Arni

et al. 1999

Chem. Eng. Technol.

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The most common kinetic models available in the literature to describe the COD consumption during batch anaerobic digestion are checked and compared in their linearized forms in the case of prehydrolyzed mixtures simulating the composition of woody wastes. The introduction of the COD value at the end of batch digestion in both the First Order and the Monod models allows one to take into account the deviations due to the progressive increase in the fraction of difficultly-digestible substances present in the medium. The so-modified version of the First Order model as well as that proposed by Singh and co-workers not only show the best fits to the experimental data but also demonstrate that they are the simplest and easiest ones for immediate use.

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Biogenesis of Methane

Cited by 303 publications

References 1 publication

Partial purification and characterization of F₄₂₀-dependent NADP reductase from Methanobrevibacter smithii strain DE1

Partial purification and characterization of F₄₂₀-dependent NADP reductase from Methanobrevibacter smithii strain DE1

Purification and characterization of fumarate reductase from Methanobacterium thermoautotrophicum

Linearized Kinetic Models for the Simulation of the Mesophilic Anaerobic Digestion of Pre-hydrolyzed Woody Wastes

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