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PubMed1985

Effect of Acarbose on the production of hydrogen and methane and on hormonal parameters in young adults under standardized low-fibre mixed diets.

Short and middle term effects of Acarbose were studied in volunteers on a standardized, low-fibre, mixed diet for the development of tolerance phenomena with gas exhalations and some peptide hormone levels as main parameters. Both hydrogen and methane were measured quantitatively as diurnal profiles. Acarbose caused an about 20-fold increase of H2 exhalation and had only moderate effects on methane production, indicating the presence of fermentable carbohydrates in the large bowel. Methanogenic individuals exhaled significantly less H2 than did non-methanogenic subjects. Changes in blood glucose, serum insulin, GIP, gastrin, and plasma glucagon, caused by Acarbose, reflected delayed glucose absorption and were plausible within the regulatory framework of carbohydrate assimilation. When the Acarbose regime was maintained for 5 weeks on a controlled diet, abdominal sensations like e.g. meteorism declined remarkably while carbohydrate fermentation remained high and lowered GIP was sustained. Thus functional responses of the gastro-intestinal tract to altered carbohydrate supplies, elicited by Acarbose, were found by 3 independent parameters: anaerobic gas production, peptide hormone levels, and subjective abdominal sensations. The objective parameters seem to remain constant in the longer run, while subjective parameters show long-term adaptation.

Acarbose↗
PubMed1982

Anaerobic degradation of cellulose and formation of methane.

The existing knowledge of anaerobic digestion of cellulose-containing wastes and methane formation is reviewed. Mutual relationships between the individual phases of this complex process and the mechanism of methane biosynthesis are discussed in three sections: (1) Non-methanogenic phase and digestion of cellulose; (2) methanogenic phase and methanogenesis; (3) mixed cultures and their advantages.

Anaerobiosis↗
PubMed2005

Methane-oxidizing bacteria in a Finnish raised mire complex: effects of site fertility and drainage.

Methane-oxidizing bacteria (MOB) are the only biological sinks for methane (CH4). Drainage of peatlands is known to decrease overall CH4 emission, but the effect on MOB is unknown. The objective of this work was to characterize the MOB community and activity in two ecohydrologically different pristine peatland ecosystems, a fen and a bog, and their counterparts that were drained in 1961. Oligotrophic fens are groundwater-fed peatlands, but ombrotrophic bogs receive additional water and nutrients only from rainwater. The sites were sampled in August 2003 down to 10 cm below the water table (WT), and cores were divided into 10-cm subsamples. CH4 oxidation was measured by gas chromatography (GC) to characterize MOB activity. The MOB community structure was characterized by polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE) and sequencing methods using partial pmoA and mmoX genes. The highest CH4 oxidation rates were measured from the subsamples 20-30 and 30-40 cm above WT at the pristine oligotrophic fen (12.7 and 10.5 micromol CH4 dm-3 h-1, respectively), but the rates decreased to almost zero in the vicinity of WT. In the pristine ombrotrophic bog, the highest oxidation rate at 0-10 cm was lower than in the fen (8.10 micromol CH4 dm-3 h-1), but in contrast to the fen, oxidation rates of 4.5 micromol CH4 dm-3 h-1 were observed at WT and 10 cm below WT. Drainage reduced the CH4 oxidation rates to maximum values of 1.67 and 5.77 micromol CH4 dm-3 h-1 at 30-40 and 20-30 cm of the fen and bog site, respectively. From the total of 13 pmoA-derived DGGE bands found in the study, 11, 3, 6, and 2 were observed in the pristine fen and bog and their drained counterparts, respectively. According to the nonmetric multidimensional scaling of the DGGE banding pattern, the MOB community of the pristine fen differed from the other sites. The majority of partial pmoA sequences belonged to type I MOB, whereas the partial mmoX bands that were observed only in the bog sites formed a distinct group relating more to type II MOB. This study indicates that fen and bog ecosystems differ in MOB activity and community structure, and both these factors are affected by drainage.

Bacteria↗
PubMed2002

Effects of nitrite and ammonium on methane-dependent denitrification.

For effective application of methane-dependent denitrification (MDD) in the treatment of wastewater containing NO(2)(-) or NH(4)(+), the effect of these inorganic nitrogen compounds on MDD activity needs to be clarified. The MDD activity of sludge acclimatized with CH(4) and O(2) was determined with mineral media of different nitrogen-compound compositions in the presence of 0.21 atm CH(4) and 0.20 atm O(2). Incubations with media containing only NO(2)(-) or two of the three inorganic nitrogen compounds (NO(3)(-)+NO(2)(-), NO(2)(-)+NH(4)(+) or NH(4)(+)+NO(3)(-)) resulted in MDD activity equal to or higher than that with media containing only NO(3)(-). However, there was no MDD activity in media containing NO(2)(-) at 10 degrees C, probably because of serious inhibition of NO(2)(-) on methane oxidation. MDD occurred in media containing only NH(4)(+), although the total nitrogen removal efficiency was very low. These results show that NO(2)(-) and NH(4)(+), in the presence of NO(x)(-), do not inhibit but rather promote MDD. Consequently, NH(4)(+) does not need to be completely oxidized to NO(3)(-) in the nitrification reactor before MDD. However, under psychrophilic conditions, NO(2)(-) seriously inhibited MDD. Therefore, the nitrification reactor must not discharge effluent containing NO(2)(-) under psychrophilic conditions.

Methane↗
PubMed2000

Inhibition of methane production from whey by heavy metals--protective effect of sulfide.

A whey solution was used as a substrate for methane production in an anaerobic fixed-bed reactor. At a hydraulic retention time of 10 days, equivalent to a space loading of 3.3 kg (m3 day)(-1), 90% of the chemical oxygen demand was converted to biogas. Only a little propionate remained in the effluent. Toxicity tests with either copper chloride, zinc chloride or nickel chloride were performed on effluent from the reactor. Fifty per cent inhibition of methanogenesis was observed in the presence of > or =10 mg CuCl2 l(-1) > or =40 mg ZnCl2 l(-1) and > or =60 mg NiCl2 l(-1), respectively. After exposure to Cu2+, Zn2+ or Ni2+ ions for 12 days, complete recovery of methanogenesis by equimolar sulfide addition was possible upon prolonged incubation. Recovery failed, however, for copper chloride concentrations > or =40 mg l(-1). If the sulfide was added simultaneously with the three heavy metal salts, methanogenesis was only slightly retarded and the same amount of methane as in non-inhibited controls was reached either 1 day (40 mg ZnCl2 l(-1) or 2 days later (10 mg CuCl2 l(-1)). Up to 60 mg NiCl2 l(-1) had no effect if sulfide was present. Sulfide presumably precipitated the heavy metals as metal sulfides and by this means prevented heavy metal toxicity.

Anaerobiosis↗
PubMed2004

Analysis and application of ADM1 for anaerobic methane production.

An anaerobic model for the serum bottle test was developed and analyzed with sensitivities of stoichiometric and kinetic parameters to the components in order to establish a basis for appropriate application of the model. Anaerobic glucose degradation in a serum bottle was selected as an example. The anaerobic model was developed based on the anaerobic digestion model no. 1 (ADM1), which had five processes with 17 kinetic and stoichiometric parameters. Sensitivity analysis showed that the yield of product on the substrate (f) has high sensitivities to model components, and that the methane concentration was the most sensitive component. Important parameters including yield of product on the substrate (f), yield of biomass on the substrate (Y), and half-saturation values (K) were estimated using genetic algorithms, which optimized the parameters with experimental results. The Monod maximum specific uptake rate (k) was, however, so strongly associated with the concentration of biomass, that values could not be estimated individually. Simulation with estimated parameters showed good agreement with experimental results in the case of methane production. However, there were some differences in acetate and propionate concentrations.

Algorithms↗
PubMed2004

High-rate thermophilic methane fermentation on short-chain fatty acids in a down-flow anaerobic packed-bed reactor.

In order to maximize the efficiency of methane fermentation on short-chain fatty acids, growth media containing acetic acid and butyric acid as major carbon sources were supplied to a thermophilic down-flow anaerobic packed-bed reactor. The organic loading rate (OLR) to the reactor ranged from 0.2 to 169 kg-dichromate chemical oxygen demand(CODcr)/m(3)-reactor/day, corresponding to a hydraulic retention time (HRT) of between 1.4 h and 20 days. Stable methane production was maintained at HRTs as short as 2 h (OLR=120 kg-CODcr/m(3)/day), with the short-chain fatty acids in the feed almost completely removed during the process. The apparent substrate removal efficiency, determined from the total CODcr values in the influent and effluent, was 75% at short HRTs. However, the actual substrate removal efficiency must have been greater than 75%, since a fraction of substrate was also utilized in microbial cell synthesis, and these cells were part of the measured total CODcr.

Acetic Acid↗
PubMed2006

Decomposition of reactive oxygen species by copper(II) bis(1-pyrazolyl)methane complexes.

Two bis(1-pyrazolyl)alkane ligands, bis(3,5-dimethyl-1-pyrazolyl)methane and bis(4-iodo-3,5-dimethyl-1-pyrazolyl)methane, and their copper(II) complexes, bis(3,5-dimethyl-1-pyrazolyl)methanedinitratocopper(II) [CuL1(NO3)2] and bis(4-iodo-3,5-dimethyl-1-pyrazolyl)methanedinitratocopper(II) [CuL2(NO3)2] x 2H2O, were prepared. Physiochemical properties of the copper(II) complexes were studied by spectroscopic (UV-vis, IR, EPR) techniques and cyclic voltammetry. Spectroscopic analysis revealed a 1:1 stoichiometry of ligand:copper(II) ion and a bidentate coordination mode for the nitrate ions in both of the complexes. According to experimental and theoretical ab initio data, the copper(II) ion is located in an octahedral hexacoordinated environment. Both complexes were able to catalyze the dismutation of superoxide anion (O2*-) (pH 7.5) and decomposition of H2O2 (pH 7.5) and peroxynitrite (pH 10.9). In addition, both complexes exhibited superoxide dismutase (SOD) like activity toward extracellular and intracellular reactive oxygen species produced by activated human neutrophils in whole blood. Thus, these complexes represent useful SOD mimetics with a broad range of antioxidant activity toward a variety of reactive oxidants.

Copper↗
PubMed1986

Tetrahydromethanopterin methyltransferase, a component of the methane synthesizing complex of Methanobacterium thermoautotrophicum.

A new enzyme, tetrahydromethanopterin methyltransferase, which catalyzes the transfer of methyl groups from methyl-tetrahydromethanopterin to 2-mercaptoethane-sulfonate, has been found in the methane synthesizing complex of Methanobacterium thermoautotrophicum. The enzyme is oxygen sensitive and has a well defined pH optimum at pH 6.7. There was no methyl group transfer when the enzyme was heated to 100 degrees for 5 min. The product of the forward reaction, methyl-CoM, was positively identified by TLC and high voltage paper electrophoresis. The demethylation of methyl-CoM, in the absence of methane synthesis, was dependent on the addition of H4MPT which suggests that the enzyme reaction is reversible.

Euryarchaeota↗
PubMed2004

Continuous methane fermentation and the production of vitamin B12 in a fixed-bed reactor packed with loofah.

A fixed-bed reactor with acclimated methanogens immobilized on a loofah support was studied on a laboratory scale to evaluate the system producing methane from the mixture of CO(2) and H(2) gas, with the production of vitamin B(12) as a by-product. Fermentation using CO(2)/H(2) acclimated methanogens was conducted in a jar fermentor with hydraulic retention times (HRTs) of three and six days. The performance of the reactor was mainly dependent on the HRT. With an HRT of three days, the methane production rate and the vitamin B(12) concentration in the culture broth were 6.18 l/l-reactor/h and 2.88 mg/l-culture liquid; these values were 11.96 l/l-reactor/h and 37.54 mg/l-culture liquid for an HRT of six days. A higher total cell mass of methanogens retained 42.5 g dry cell/l-culture liquid was achieved in the HRT of six days. The loofah carrier immobilized almost 95% of the methanogens, which led to a more effective bio-reaction. It was also observed that the fermentation system had a better ability to buffer pH, especially for an HRT of six days.

Bioreactors↗
PubMed2005

Preparation of carbon molecular sieves by carbon deposition from methane.

To prepare carbon molecular sieves (CMSs), methane was pyrolyzed in an attempt to deposit fine carbon particles on the micropore mouths of the carbon substrates being heated; the carbon substrates included grain-based activated carbons and commercial activated carbons. To explore the effects of heat treatment alone, blank experiments were conducted by heating the samples in N2. The resultant products were characterized by N2-adsorption at 77K. Methane failed to deposit carbon at 800 degrees C. The porosity of activated carbons, however, was substantially influenced by heat treatment alone. The surface areas and micropore volumes of the activated carbons from grain sorghum decreased by 39.32% and 36.84%, respectively, upon heat treatment alone; this is attributable to the destruction of pore structure by sintering. In contrast, the corresponding values of the commercial activated carbons increased by 59.86% and 62.16%, respectively, upon heat treatment alone; this can be attributable to the development of microporosity.

Adsorption↗
PubMed2006

Emission of methane and carbon dioxide and earthworm survival during composting of pharmaceutical sludge and spent mycelia.

Emissions of methane (CH4) and carbon dioxide (CO2) from spent mycelia of the mold Penicilium notatum and sludge from the effluent treatment facility (ETPS) of a pharmaceutical industry were estimated twice during a two-week composting before vermicomposting. These wastes are dumped in landfills or sometimes used in agricultural fields and no reports are available on their greenhouse gas producing potentials. The solid wastes contained appreciable organic carbon and nitrogen while very high Fe, Mn and Zn were found in ETPS only. Pure wastes did not support germination of Vigna radiata L. while mixing soil with ETPS and spent mycelia at the ratios of 12:1 and 14:1 led to 80% and 50% germination, respectively. The wastes were mixed with cowdung at the ratios of 1:1, 1:3 and 3:1 for composting. Carbon dioxide emissions were always significantly higher than CH4 emissions from all the treatments due to prevalence of aerobic condition during composting. From some treatments, CH4 emissions increased with time, indicating increasing activity of anaerobic bacteria in the waste mixtures. Methane emissions ranged from 21.6 to 231.7 microg m(-2) day(-1) while CO2 emissions were greater than thousand times at 39.8-894.8 mg m(-2) day(-1). The amount of C emitted as CH4-C and CO2-C from ranged from 0.007% to 0.081% of total C composted. Cowdung emitted highest CH4 followed by spent mycelia and ETPS while ETPS emitted more CO2 than spent mycelia but lesser than cowdung. Global warming potential of emitted CH4 was found to be in the range of 10.6-27.7 mg-CO2-equivalent on a 20-year time horizon. The results suggest that pharmaceutical wastes can be an important source of CH4 and CO2 during composting or any other stockpiling under suitable moisture conditions. The waste mixtures were found not suitable for vermicomposting after two weeks composting and earthworms did not survive long in the mixtures.

Animals↗
PubMed2006

Anaerobic co-digestion of algal sludge and waste paper to produce methane.

The unbalanced nutrients of algal sludge (low C/N ratio) were regarded as an important limitation factor to anaerobic digestion process. Adding high carbon content of waste paper in algal sludge feedstock to have a balanced C/N ratio was undertaken in this study. The results showed adding 50% (based on volatile solid) of waste paper in algal sludge feedstock increased the methane production rate to 1170+/-75 ml/l day, as compared to 573+/-28 ml/l day of algal sludge digestion alone, both operated at 4 g VS/l day, 35 degrees C and 10 days HRT. The maximum methane production rate of 1607+/-17 ml/l day was observed at a combined 5 g VS/l day loading rate with 60% (VS based) of paper adding in algal sludge feedstock. Results suggested an optimum C/N ratio for co-digestion of algal sludge and waste paper was in the range of 20-25/1.

Anaerobiosis↗
PubMed2006

Characterisation of solid and liquid fractions of dairy manure with regard to their component distribution and methane production.

Dairy manure with a total solids content of 77.2g TS/l was separated by means of screening and coagulation-flocculation treatments, using CaO as coagulant and a cationic polyacrylamide as flocculant, obtaining liquid and solid fractions. The solid fraction separated contained 33.4% of the initial total mass of dairy manure plus chemical solutions, containing also 75.2% of the TS, 80.4% of the VS, 58.5% of the total Kjeldahl nitrogen (TKN) and 87.4% of the total phosphorus (P(T)) present in the initial dairy manure. 83.7% of the liquid fraction chemical oxygen demand (COD) was anaerobically biodegradable (COD(BD)). Methane production for the separated liquid fraction was 0.604l CH4 NCTP/g VS added, being 0.307 and 0.371l CH4 NCTP/g VS added for dairy manure and screened dairy manure, respectively. The characteristics of this liquid fraction would allow its treatment in high loading anaerobic reactors having shorter hydraulic retention times, smaller reactor size and a higher methane volumetric production rate than conventional anaerobic reactors treating either manure or screened manure.

Anaerobiosis↗
PubMed2006

Regression models of ultimate methane yields of fruits and vegetable solid wastes, sorghum and napiergrass on chemical composition.

Several fractions of fruits and vegetable solid wastes (FVSW), sorghum and napiergrass were analyzed for total solids (TS), volatile solids (VS), total organic carbon, total kjeldahl nitrogen, total soluble carbohydrate, extractable protein, acid-detergent fiber (ADF), lignin, cellulose and ash contents. Their ultimate methane yields (B(o)) were determined using the biochemical methane potential (BMP) assay. A series of simple and multiple regression models relating the B(o) to the various substrate constituents were generated and evaluated using computer statistical software, Statistical Package for Social Sciences (SPSS). The results of simple regression analyses revealed that, only weak relationship existed between the individual components such as carbohydrate, protein, ADF, lignin and cellulose versus B(o). A regression of B(o) versus combination of two variables as a single independent variable such as carbohydrate/ADF and carbohydrate+protein/ADF also showed that the relationship is not strong. Thus it does not appear possible to relate the B(o) of FVSW, sorghum and napiergrass with single compositional characteristics. The results of multiple regression analyses showed promise and the relationship appeared to be good. When ADF and lignin/ADF were used as independent variables, the percentage of variation accounted for by the model is low for FVSW (r(2)=0.665) and sorghum and napiergrass (r(2)=0.746). Addition of nitrogen, ash and total soluble carbohydrate data to the model had a significantly higher effect on prediction of B(o) of these wastes with the r(2) values ranging from 0.9 to 0.99. More than 90% of variation in B(o) of FVSW could be accounted for by the models when the variables carbohydrate, lignin, lignin/ADF, nitrogen and ash (r(2)=0.904), carbohydrate, ADF, lignin/ADF, nitrogen and ash (r(2)=0.90) and carbohydrate/ADF, lignin/ADF, lignin and ash (r(2)=0.901) were used. All the models have low standard error values, which indicate the amount of spread is less. Thus, considering only the higher r(2) values, six models are proposed for predicting the B(o) based on FVSW data and sorghum and napiergrass data. It would be more convenient if B(o) could be predicted by analyzing the chemical composition of the substrate rather than performing the long-term batch fermentation. To test the validity of the regression models, chemical constituents of FVSW that were not included in the regression analyses were determined and their experimental B(o) were determined by BMP assay. All the six models were used to predict the B(o) from the chemical constituents of these FVSW. It was found that most of the predicted values were within 20% of the experimental B(o) in models 1, 3 and 6. Since models 3 and 6 used the same variables namely, total soluble carbohydrate, ADF, lignin/ADF, nitrogen and ash, B(o) can be predicted from these five chemical constituents which accounts for more than 90% of the variation in B(o) (r(2)>90).

Fruit↗
PubMed2004

Catalytic combustion of methane over commercial catalysts in presence of ammonia and hydrogen sulphide.

The performance of different commercially available catalysts (supported Pd, Pt, Rh, bimetallic Pd-Pt, and Cr-Cu-Ti oxide catalyst) for the oxidation of methane, alone and in presence of ammonia and hydrogen sulphide is studied in this work. Catalysts performance was evaluated both in terms of activity and resistance to poisoning. The main conclusions are that supported Pd and Rh, present the highest activities for methane oxidation, both alone and in presence of ammonia, whereas they are severely poisoned in presence of H2S. Pt and Cr-Cu-Ti are less active but more sulphur resistant, but their activity is lower than the residual activity of sulphur-deactivated Pd and Rh catalysts. The Pd-Pt catalyst exhibits low activity and it is quickly deactivated in presence of hydrogen sulphide.

Ammonia↗
PubMed2004

Evaluation of the pulsed discharge helium ionization detector for the analysis of hydrogen and methane in breath.

Under the appropriate separation conditions the pulsed discharge helium ionization detector (PDHID) was used to detect hydrogen and methane separated from the matrix components of human breath samples. The sensitivity of this method is over an order of magnitude better than published methods using a flame ionization detector (FID) and a thermal conductivity detector (TCD), and has the further advantage of detecting both analytes with only one detector. Limits of detection were 0.3 ppmv for both hydrogen and methane and the method had a linear dynamic range (LDR) of three orders of magnitude (0.3-400 ppm, v/v). The PDHID was also compared to the FID and the TCD in regard to selectivity, sensitivity and reproducibility for high-speed gas chromatography (HSGC). It was shown that the PDHID is as sensitive as the FID for fast separations but is limited by the difficulty of resolving analyte peaks from O2 and N2. The PDHID was at least three orders of magnitude more sensitive than the TCD for all of the analytes examined.

Breath Tests↗
PubMed2005

Microtrap modulated flame ionization detector for on-line monitoring of methane.

A microtrap for on-line analysis of trace methane was developed. Silicosteel tubing, 15 cm long, 1.02 mm i.d. and 1.59 mm o.d. was packed with Carbosphere 80/100 mesh and placed between the standard gas source and the flame ionization detector (FID) to be used as a preconcentrator and an injector. The sample stream was passed continuously through the microtrap that was heated at a fixed interval by an electric pulse. To achieve the highest adsorption and desorption efficiency, parameters affecting the response of the system were optimized, and adsorption temperature in the range of 25 to -50 degrees C was studied. The response from the microtrap as compared to that from direct-flame ionization detector was enhanced by as much as 260 times. The on-line microtrap system showed good linearity (r2 > 0.99), low detection limit (28.3 ppbv) and good long term stability (relative standard deviation, RSD of less than 5.0%). Therefore, this simple device is suitable for on-line analysis of trace methane and similar small molecules in the environment as in high purity gases.

Methane↗