Anaerobic degradation of protein-rich material results in the release of ammonium. An increase in levels of ammonium in biogas reactors usually results in less effective degradation and lower methane-formation rates for two reasons: Acetate-utilizing meth...

The general features are known for the pathway by which most methane is produced in nature. All acetate-utilizing methanogenic microorganisms contain CODH which catalyzes the cleavage of acetyl-CoA; however, the pathway differs from all other acetate-utilizing anaerobes in that the methyl group is reduced to methane with electrons ...

The organization and species composition of bacterial trophic groups associated with lactose biomethanation were investigated in a whey-processing chemostat by enumeration, isolation, and general characterization studies. The bacteria were spatially organized as free-living forms and as self-immobilized forms appearing in flocs. Three dominant bacterial trophic group ...

Methane fermentation has been widely used as a waste-water treatment system because of the low consumption of energy, low level of sludge production, and recovery of methane as a source of energy. In this system, acetate is the precursor for about 70% of the methane produced during the anaerobic digestion of organic compounds, and the decarboxylation of acetate is considered to be the ...

The following major advances were made in the past two years: both acetate activating enzymes were characterized and the regulation of synthesis was studied; direct biochemical evidence for the proposed function of the CODH was obtained, and the CODH comp...

Our current understanding of the pathway of acetate conversion to methane in Methanosarcina thermophila is depicted. Our accomplishments this past year include phosphotransacetylase, the corrinoid/Fe-S protein component of the carbon monoxide dehydrogenas...

Sterile granular sludge was inoculated with either Methanosarcina mazeii S-6, Methanosaeta concilii GP-6, or both species in acetate-fed upflow anaerobic sludge blanket (UASB) reactors to investigate the immobilization patterns and dynamics of aceticlastic methanogens in granular sludge. After several months of reactor operation, the ...

Acetate is the precursor of approximately two-thirds of the methane produced by anaerobic bioreactors and many other methanogenic habitats. Besides their intrinsic interest, thermophilic acetotrophic methanogenic cultures usually grow at least twice as fast as their mesophilic counterparts, making them more amenable to study. In recent years, attention has ...

Methanogenic activity in a thermophilic-dry anaerobic reactor was determined by comparing the amount of methane generated for each of the organic loading rates with the size of the total and specific methanogenic population, as determined by fluorescent in situ hybridization. A high correlation was evident between the total ...

Methanogenic activity in a thermophilic-dry anaerobic reactor was determined by comparing the amount of methane generated for each of the organic loading rates with the size of the total and specific methanogenic population, as determined by fluorescent in situ hybridization. A high correlation was evident between the total ...

Batch tests to measure maximum acetate utilization rates were used to determine the distribution of acetate utilizers in expanded-bed sand and expanded-bed granular activated carbon (GAC) reactors. The reactors were fed a mixture of acetate and 3-ethylphenol, and they contained the same predominant aceticlastic ...

Acetate conversion to methane and C0{sub 2} by the methanogenic archaebacteria is a primary rate limiting step in anaerobic biodegradative processes in nature. However, the genetic study of these organisms has not been experimentally tractable due to the inability to grow and plate the organisms as single cells, and to extract high molecular weight DNA and RNA without ...

Acetate conversion to methane and C0{sub 2} by the methanogenic archaebacteria is a primary rate limiting step in anaerobic biodegradative processes in nature. However, the genetic study of these organisms has not been experimentally tractable due to the inability to grow and plate the organisms as single cells, and to extract high molecular weight DNA and RNA without ...

A dual approach consisting of cultivation and molecular retrieval of partial archaeal 16S rRNA genes was carried out to characterize the diversity and structure of the methanogenic community inhabiting the anoxic bulk soil of flooded rice microcosms. The molecular approach identified four groups of known methanogens. Three environmental sequences clustered ...

Whole cells of the methanogen Methanosarcina barkeri were immobilized in an alginate network which was crosslinked with Ca/sup 2+/ calcium ions. The rates of methanol conversion to methane of entrapped cells were found to be in the same range as the corresponding rates of free cells. Furthermore, immobilized cells were active for a ...

The competition between acetate utilizing methane-producing bacteria (MB) and sulfate-reducing bacteria (SRB) was studied in mesophilic (30 degrees C) upflow anaerobic sludge bed (UASB) reactors (upward velocity 1 m h-1; pH 8) treating volatile fatty acids and sulfate. The UASB reactors treated a VFA mixture (with an acetate:propionate:butyrate ratio of ...

The competition between acetate utilizing methane-producing bacteria (MB) and sulfate-reducing bacteria (SRB) was studied in mesophilic (30 C) upflow anaerobic sludge bed (UASB) reactors treating volatile fatty acids and sulfate. The UASB reactors treated a VFA mixture (with an acetate:propionate:butyrate ratio of 5:3:2 on COD basis) or acetate as the sole ...

We studied syntrophic butyrate degradation in thermophilic mixed cultures containing a butyrate-degrading bacterium isolated in coculture with Methanobacterium thermoautotrophicum or in triculture with M. thermoautotrophicum and the TAM organism, a thermophilic acetate-utilizing methanogenic bacterium. Butyrate was ?-oxidized to acetate with protons as the ...

Anaerobic methane oxidation is a general process important in controlling fluxes of methane from anoxic marine sediments. The responsible organism has not been isolated, and little is known about the electron acceptors and substrates involved in the process. Laboratory evidence indicates that sulfate reducers and methanogens are able to oxidize small quantities of methane. ...

Hydrogen partial pressures were measured in a thermophilic coculture comprised of a eubacterial rod which oxidized acetate to H{sub 2} and CO{sub 2} and a hydrogenotrophic methanogen, Methanobacterium sp. strain THF. H{sub 2} partial pressures in the coculture were measured to be between 20 and 50 Pa (0.12 to 0.30 {mu}M) during acetate ...

Population development of key groups of bacteria involved in municipal refuse conversion to methane was measured from the time of initial incubation through the onset of methane production. Hemicellulolytic bacteria, cellulolytic bacteria, hydrogen-producing acetogens, and acetate-and H{sub 2}-plus-CO{sub 2}-utilizing methanogens were enumerated by the most-probable-number ...

The effect of dosing a metal limited anaerobic sludge blanket (UASB) reactor with a metal pulse on the methanogenic activity of granular sludge has thus far not been successfully modeled. The prediction of this effect is crucial in order to optimize the strategy for metal dosage and to prevent unnecessary losses of resources. This paper describes the relation between the ...

This paper describes the effect of the nutrients iron (Fe), nickel (Ni), zinc (Zn), cobalt (Co), and molybdenum (Mo) on biomass evolution in an upflow anaerobic sludge blanket (UASB) reactor metabolizing synthetic sulfate-laden organics at varying operating conditions during a period of 540 days. A bench-scale model of a UASB reactor was operated at a temperature of 35 degrees C for a chemical ...

Major acetate-utilizing bacterial and archaeal populations in methanogenic anaerobic digester sludge were identified and quantified by radioisotope- and stable-isotope-based functional analyses, microautoradiography-fluorescence in situ hybridization (MAR-FISH) and stable-isotope probing of 16S rRNA (RNA-SIP) that can directly link 16S rRNA phylogeny with ...

The methanogenic community in hydrothermally active sediments of Guaymas Basin (Gulf of California, Mexico) was analyzed by PCR amplification, cloning, and sequencing of methyl coenzyme M reductase (mcrA) and 16S rRNA genes. Members of the Methanomicrobiales and Methanosarcinales dominated the mcrA and 16S rRNA clone libraries from the upper 15 cm of the sediments. Within the ...

A bacterial consortium capable of sucrose degradation primarily to CH/sub 4/ and CO/sub 2/ was constructed, with acetate as the key methanogenic precursor. In addition, the effect of agar immobilization on the activity of the consortium was determined. The primary fermentative organism, Escherichia coli, produced acetate, formate, H/sub 2/, and CO/sub 2/ ...

Reductive dehalogenation is an important reaction that generally leads to detoxification of many halogenated methanes. This research focused on the reductive dehalogenation of chlorinated methanes in several types of systems. The first system studied the reductive dechlorination of chlorinated methanes by laboratory cultures of methanogens. A special vessel was constructed ...

A phenol-degrading methanogenic enrichment was successfully immobilized in agar as shown by the stoichiometric conversion of phenol to CH/sub 4/ and CO/sub 2/. The enrichment contained members of three physiological groups necessary for the syntrophic mineralization of phenol: a phenol-oxidizing bacterium, a Methanothrix-like bacterium, and an H/sub ...

A phenol-degrading methanogenic enrichment was successfully immobilized in agar as shown by the stoichiometric conversion of phenol to CH₄ and CO₂. The enrichment contained members of three physiological groups necessary for the syntrophic mineralization of phenol: a phenol-oxidizing bacterium, a ...

The C isotopic composition of CH4 emissions are strongly influenced by the pathway of CH4 formation. Contrary to data from other freshwater systems, soil gas and surface flux measurements made in the tropical rain forests of Puerto Rico strongly suggest that CH4 produced in these environments was derived from CO2 reduction, rather than from acetate consumption. This study explored the effects of ...

Population development of key groups of bacteria involved in municipal refuse conversion to methane was measured from the time of initial incubation through the onset of methane production. Hemicellulolytic bacteria, cellulolytic bacteria, hydrogen-producing acetogens, and acetate- and H(2)-plus-CO(2)-utilizing methanogens were enumerated by the most-probable-number technique ...

Population development of key groups of bacteria involved in municipal refuse conversion to methane was measured from the time of initial incubation through the onset of methane production. Hemicellulolytic bacteria, cellulolytic bacteria, hydrogen-producing acetogens, and acetate- and H₂-plus-CO₂-utilizing methanogens were ...

Investigations into the biochemistry and physiology of the four major groups of microorganisms (primary, ancillary, secondary and methane bacteria) involved in the anaerobic conversion of cellulose to methane and carbon dioxide are presented. The investigations of the ancillary bacteria emphasize the isolation of new strains and increasing ethanol production with T. ethanolicus. These studies ...

Inhibition of the fermentation of acetate to methane and carbon dioxide by acetate was analyzed with an acetate-acclimatized sludge and with Methanosarcina barkeri Fusaro under mesophilic conditions. A second-order substrate inhibition model, q{sub CH{sub 4}} = q{sub m}S/(K{sub s} + S + (S{sup 2}/K{sub i})), where S was the concentration of undissociated acetic acid, not ionized acetic acid, could ...

Inhibition of the fermentation of acetate to methane and carbon dioxide by acetate was analyzed with an acetate-acclimatized sludge and with Methanosarcina barkeri Fusaro under mesophilic conditions. A second-order substrate inhibition model, q_ch4 = q_mS/[K_s + S + ...

Kinetics of butyrate, acetate, and hydrogen metabolism were determined with butyrate-limited, chemostat-grown tricultures of a thermophilic butyrate-utilizing bacterium together with Methanobacterium thermoautotrophicum and the TAM organism, a thermophilic acetate-utilizing methanogenic rod. Kinetic parameters were determined from progress curves fitted to ...

A system is described that combines the fermentation of cellulose to acetate, CH4, and CO2 by Ruminococcus albus and Methanobrevibacter smithii with the fermentation of acetate to CH4 and CO2 by Methanosarcina barkeri to convert cellulose to CH4 and CO2. A cellulose-containing medium was pumped into a co-culture of the cellulolytic R. albus and the H2-using methanogen, Mb. ...

The development of granular sludge in thermophilic (55 degrees C) upflow anaerobic sludge blanket reactors was investigated. Acetate and a mixture of acetate and butyrate were used as substrates, serving as models for acidified wastewaters. Granular sludge with either Methanothrix or Methanosarcina as the predominant acetate utilizing ...

The goal of our study was to determine the dominant substrates being used by methanogens in salt ponds in Guerrero Negro, Baja California Sur, Mexico. These are extreme environments that have been used as analogs for ancient life, terrestrial and extraterrestrial. Microbial mat and/or sediments from the ponds, amended either with site water only (controls) or with site water ...

Fluoride is a common contaminant in a variety of industrial wastewaters. Available information on the potential toxicity of fluoride to microorganisms implicated in biological wastewater treatment is very limited. The objective of this study was to evaluate the inhibitory effect of fluoride towards the main microbial populations responsible for the removal of organic constituents and nutrients in ...

Although obligate syntrophic reactions cannot proceed without hydrogenotrophs, it has been unclear from the literature whether potential improvements are achievable with higher concentrations of hydrogenotrophs. In this study, the relative importance of formate-/H₂-utilizing and acetate-utilizing trophic groups in the anaerobic degradation of butyrate and propionate was ...

In order to overcome the disadvantages of the anaerobic reactor such as slow growth and long start-up, the flocculent anaerobic sludge was embedded and used as the seed sludge in the anaerobic treatment of PTA wastewater with the objective of keeping biomass in the reactor. The start-up characteristics of the UASB reactor were investigated. During the 136 days' running, COD removal rate of PTA ...

Concurrent geochemical analyses of porewater and genetic analyses of wetland sediment over time in laboratory microcosm experiments are being used to define biodegradation pathways of 1,1,2,2-tetrachloroethane (PCA) and associated critical microorganisms in anaerobic wetland sediments. These experiments were conducted to better understand factors controlling in situ daughter product distribution ...

In fermentative hydrogen production, the low-hydrogen-producing bacteria retention rate limits the suspended growth reactor productivity because of the long hydraulic retention time (HRT) required to maintain adequate bacteria population. Traditional bacteria immobilization methods such as calcium alginate entrapment have many application limitations in hydrogen fermentation, ...

A mixed culture of human fecal bacteria was grown for 120 days in a three-stage continuous culture system. To reproduce some of the nutritional and pH characteristics of the large gut, each vessel had a different operating volume (0.3, 0.5, and 0.8 liter) and pH (6.0, 6.5, and 7.0). A mixture of polysaccharides and proteins was used as carbon and nitrogen sources. Measurements of H2, CH4, S2-, ...

A convenient method for evaluation of biochemical reaction rate coefficients and their uncertainties is described. The motivation for developing this method was the complexity of existing statistical methods for analysis of biochemical rate equations, as well as the shortcomings of linear approaches, such as Lineweaver-Burk plots. The nonlinear least-squares method provides accurate estimates of ...

The microbial community in a full-scale anaerobic digester (2300m3) treating industrial food waste in the Kyoto Eco-Energy Project was analyzed using terminal restriction fragment length polymorphism for eubacterial and archaeal 16S rRNA genes. Both thermophilic and mesophilic sludge of treated swine waste were seeded to the digestion tank. During the 150-day startup period, coffee grounds as a ...

Our current understanding of the pathway of acetate conversion to methane in Methanosarcina thermophila is depicted. Our accomplishments this past year include phosphotransacetylase, the corrinoid/Fe-S protein component of the carbon monoxide dehydrogenase, and ferredoxin were characterized in further detail; two methyl transferase activities were resolved; and putative positive clones containing ...

Several enzymes in the pathway of acetate conversion to methane and carbon dioxide have been purified from Methanosarcina thermophila. The mechanisms of these enzymes are under investigation utilizing biochemical, biophysical and molecular genetic approaches. Acetate kinase and phosphotransacetylase catalyzes the activation of acetate to acetyl-CoA. The primary structure of these enzymes will be ...

Several enzymes in the pathway of acetate conversion to methane and carbon dioxide have been purified from Methanosarcina thermophila. The mechanisms of these enzymes are under investigation utilizing biochemical, biophysical and molecular genetic approaches. Acetate kinase and phosphotransacetylase catalyzes the activation of acetate to acetyl-CoA. The primary structure of these enzymes will be ...

The Powder River Basin (PRB), located in northeastern Wyoming (USA), is a principle producer of coal bed methane world-wide. The basin contains an extensive natural gas well network, which combined with past studies, facilitates a unique opportunity to study the coupling of hydrology and microbial methane generation. Microbes generate methane via two metabolic pathways, acetate fermentation and ...

A thermophilic upflow anaerobic sludge blanket (UASB) reactor degrading acetate was started by applying published methods (W. M. Wiegant and A. W. A. de Man, Biotechnol. Bioeng. 28:718-77, 1986) for production of granules dominated by Methanothrix spp. The reactor was inoculated with thermophilic digested sludge. No granules were observed during the first 7 months of start-up of the UASB reactor. ...

BackgroundThe archaeon, Methanosarcina acetivorans strain C2A forms methane, a potent greenhouse gas, from a variety of one-carbon substrates and acetate. Whereas the biochemical pathways leading to methane formation are well understood, little is known about the expression of the many of the genes that encode proteins needed for carbon flow, electron transfer and/or energy conservation. ...

Acetate is a key intermediate in the anaerobic degradation of organic matter. In anoxic environments, available acetate is a competitive substrate for sulfate-reducing bacteria (SRB) and methane-producing archaea. Little is known about the fractionation of carbon isotopes by sulfate reducers. Therefore, we determined carbon isotope compositions in cultures of three ...

When grown in the absence of added sulfate, cocultures of Desulfovibrio desulfuricans or Desulfovibrio vulgaris with Methanobrevibacter smithii (Methanobacterium ruminantium), which uses H2 and CO2 for methanogenesis, degraded lactate, with the production of acetate and CH4. When D. desulfuricans or D. vulgaris was grown in the absence of added sulfate in coculture with Methanosarcina barkeri ...

When grown in the absence of added sulfate, cocultures of Desulfovibrio desulfuricans or Desulfovibrio vulgaris with Methanobrevibacter smithii (Methanobacterium ruminantium), which uses H(2) and CO(2) for methanogenesis, degraded lactate, with the production of acetate and CH(4). When D. desulfuricans or D. vulgaris was grown in the absence of added sulfate in coculture with Methanosarcina ...

A study of the second step or methanogenic stage of a two-stage anaerobic digestion process treating two-phase olive oil mill solid residue (OMSR) was conducted at mesophilic temperature (35 degrees C). The substrate fed to the methanogenic step was the effluent from a hydrolytic-acidogenic reactor operating at an organic loading rate (OLR) of 12.9 g ...

This study was on the design and development of an immobilized cell bioreactor for the conversion of alcohol stillage to methane. The study also included the development of optimization methods for the inoculation and operation of the reactor, and the quantitation of mass transfer limitations within the immobilized biomass. A two-stage fixed-film ...

Interactions between anaerobic biofilms and heavy metals such as iron, cobalt or nickel are largely unknown. Magnetic resonance imaging (MRI) is a non-invasive method that allows in situ studies of metal transport within biofilm matrixes. The present study investigates quantitatively the penetration of iron (1.75 mM) bound to ethylenediaminetetraacetate (EDTA) into the ...

A two-column pilot scale downflow percolating fixed film (DPFF) anaerobic reactor treating deproteinized cheese whey (DPW) was used in this study. The system was operated at one-third of the maximum working volume in an attempt to avoid mass transfer limitations of the gas products (since two-thirds of the immobilized microbial culture was unsubmerged), as well as to minimize ...

High-rate anaerobic digestion can be applied in upflow anaerobic sludge blanket reactors for the treatment of various wastewaters. In upflow anaerobic sludge blanket reactors, sludge retention time is increased by a natural immobilization mechanism (viz. the formation of a granular type of sludge). When this sludge is cultivated on acid-containing wastewater, the granules ...