Inhibition Of Methane Production Research Articles

Properties of a novel series of inhibitors of rumen methanogenesis; in vitro and in vivo experiments including growth trials on 2,4-bis (trichloromethyl)-benzo [1, 3]dioxin-6-carboxylic acid.

1. A procedure for measuring methane production by rumen contents incubated anaerobically in vitro is described. Assessments of methane production in vivo, in both sheep and cattle, were made by withdrawal of rumen contents and measuring their capacity to produce methane in vitro. 2. Many members of a series of 6-substituted 2,4-bis (trichloromethyl)-benzo[1,3]dioxins were potent inhibitors of methanogenesis by rumen contents in vitro. The most potent compound inhibited methane production by 70% or more at a concentration of 1 microgram/ml (approximately 2.5 mumol/l). 3. Two compounds, namely the 6-carboxylic acid (ICI 13409) and the 6-carboxamide (ICI 43586), caused a large inhibition of methanogenesis sustained for many hours, following a single intrarumen injection in sheep or cattle. Inhibition was maintained for long periods by single daily dosing directly into the rumen or by dietary administration. 4. In a 28-week growth trial in beef cattle inclusion of ICI 13409 in the concentrate element of the diet, at a level of 6 mg/kg body-weight, improved live-weight gain by 8.0% (P less than 0.05) with respect to untreated animals whilst reducing food intake by 5.0% (P less than 0.05). Smaller and not statistically-significant effects were seen with this compound at 3 mg/kg body-weight and with the antibiotic monensin (Romensin; Elanco PLC). All treatments significantly improved the retention of dietary energy into the carcass, offal and intestinal tracts of the trial animals and significantly reduced the quantity of methane eructed into expired gases.

Kinetic Analysis of Competition Between Sulfate Reducers and Methanogens for Hydrogen in Sediments

The competition between sulfate-reducing and methanogenic bacteria for hydrogen was investigated in eutrophic lake sediments that contained low in situ sulfate concentrations and in sulfate-amended sediments. Sulfate reduction and methane production coexisted in situ in lake surface sediments (0 to 2 cm), but methane production was the dominant terminal process. Addition of 10 to 20 mM sulfate to sediments resulted in a decrease in the hydrogen partial pressure and a concomitant inhibition of methane production over time. Molybdate inhibition of sulfate reduction in sulfate-amended sediments was followed by an increase in the hydrogen partial pressure and the methane production rate to values comparable to those in sediments not amended with sulfate. The sulfate reducer population had a half-saturation constant for hydrogen uptake of 141 pascals versus 597 pascals for the methanogen population. Thus, when sulfate was not limiting, the lower half-saturation constant of sulfate reducers enabled them to inhibit methane production by lowering the hydrogen partial pressure below levels that methanogens could effectively utilize. However, methanogens coexisted with sulfate reducers in the presence of sulfate, and the outcome of competition at any time was a function of the rate of hydrogen production, the relative population sizes, and sulfate availability.

'Lactate type' response of ruminal fermentation to chloral hydrate, chloroform and trichloroethanol.

In ruminal fluid, taken from a cow 2 h after cereal feeding and supplemented with powdered grass, chloral hydrate diminished the rate of acetate, butyrate and propionate production. Instead, a considerable increase in lactate production was elicited by the drug. Chloroform and trichloroethanol had the same effect. Chloral hydrate and chloroform rendered the redox potential more negative which indicates inhibition of methane production. A concentration of chloral hydrate (2 mM), giving complete methane inhibition, reduced volatile fatty acid production by 30%. The findings are explained by assuming that chloral hydrate blocks methane production but in addition is inhibitory at a step below lactate in the reductive pathway to propionate and that the conditions chosen resulted in substrate saturation of one of the enzymes in the succinate pathway to propionate.

Lactam restriction of peptide conformation in cyclic hexapeptides which alter rumen fermentation.

gamma, delta- and epsilon-lactam containing cyclic hexapeptide analogs of cyclo-(Ala-Sar)3 have been prepared by cyclotrimerization. The analogs are covalently bridged between the methyl groups of the alanine and sarcosine residues. Only the delta-lactam of the S configuration shows the same ability as cyclo-(Ala-Sar)3 to inhibit methane production in the fermentation in rumen stomach fluid. The lactam rings of different size therefore offer a sensitive probe of the bioactive conformation of a peptide.

Blockage of methanogenesis in marine sediments by the nitrification inhibitor 2-chloro-6-(trichloromethyl) pyridine (Nitrapyrin or N-Serve)

Nitrapyrin or N-Serve [2-chloro-6-(trichloromethyl)pyridine] blocked methanogenesis associated with slurries of marine sediments. Both nitrapyrin and chloroform, an established inhibitor of methanogenic bacteria, were effective at micromolar concentrations. Chemical hydrolysis of nitrapyrin resulted in the release of three molar equivalents of chloride ions and the loss of its ability to inhibit methane production. Thus, the potency of nitrapyrin in blocking methanogenesis seemed to depend upon its trichloromethyl moiety; this conclusion was supported in experiments with other substituted pyridine compounds.

The role of cryoprotective agents as hydroxyl radical scavengers

The classic cryoprotective agents dimethylsulfoxide and glycerol are hydroxyl radical scavengers. In addition the cryoprotective agents tetramethylurea, dimethylformide, dimethylurea and monomethylurea act as hydroxyl radical scavengers as shown by the inhibition of ethylene production from methional and the inhibition of methane production from dimethylsulfoxide. Both cryoprotection and scavenger efficiency decrease in the same order within a homologous series: tetramethylurea > dimethylurea > monomethylurea. Urea does not act as a hydroxyl radical scavenger and urea is not a cryoprotective agent. Thus cryoprotection may involve scavengers in the prevention of membrane damage by hydroxyl radicals.

Inhibition of methane production by Methanobacterium formicicum

The effects of volatile fatty acids, ammonia and copper on methane production by growing cultures of Methanobacterium formicicum were studied. Acetate and butyrate were not inhibitory, but propionate was inhibitory above certain concentrations, as was ammonia. Copper was inhibitory, but inhibitory concentrations are difficult to define as varying amounts may be precipitated as the sulphide. The results are compared with those from piggery-waste digesters and it is suggested that failure of farm-waste digesters from such inhibitions is unlikely.

The effect of inhibitors of methane production on fermentation pattern and stoichiometry in vitro using rumen contents from sheep given molasses.

1. The fermentation in the presence of four known methane inhibitors was investigated in rumen contents from sheep given molassesad lib.and showing two different fermentation patterns.2. The average hydrogen recoveries obtained with the high butyrate and high propionate patterns were 93 ± 2 and 95 ± 2% respectively.3. Sodium sulphite, chloral hydrate and a hemiacetal of chloral and starch (HCS) all inhibited methane production, and were associated with an accumulation of hydrogen and lactate in rumen contents showing the high butyrate fermentation pattern. Propionate production was slightly stimulated.4. In rumen contents showing the high propionate fermentation pattern, linseed-oil hydrolysate depressed methane production at high levels only, increased hydrogen and lactate production but depressed all other products, and HCS depressed methane production and slightly increased propionate production.5. Low hydrogen recoveries in the presence of the inhibitors were probably associated with the utilization of metabolic hydrogen in reactions not accounted for in the scheme under investigation.

Dissimilation of 1,2-propanediol by rumen micro-organisms.

1. The main products of fermentation of 1,2-propanediol weren-propanol and propionic acid, but variable amounts of acetic acid and carbon dioxide were also formed. The concentrations of an intermediate propionaldehyde increased and then decreased.2. A tentative scheme is suggested, showing that 1,2-propanediol is first dehydrated to propionaldehyde, which is then reduced ton-propanol. The scheme also explains the formation of propionic and acetic acids and shows how the metabolism of 1,2-propanediol is related to that of rhamnose.3. Experiments with samples of rumen contents from animals on various diets showed that 1,2-propanediol was metabolized most rapidly when the animals were given molassed sugar-beet pulp. The rates of dissimilation of the diol increased with the concentration of rumen contents and with the concentration of substrate.4. The dissimilation of 1,2-propanediol by rumen micro-organisms resulted in an increased uptake of hydrogen. The metabolic hydrogen, arising from the inhibition of methane production by chloroform, appeared to be better utilized than the gaseous hydrogen.5. Oxygen gas did not affect the utilization of 1,2-propanediol, but the diol increased the uptake of oxygen by the rumen contents. The hydrogen and carbon balances were better when 1,2-propanediol was incubated anaerobically than in the presence of oxygen.

Effect of Chlorinated Aliphatic Acids on Gas and Volatile Fatty Acid Production in Anaerobic Soil

AbstractBy means of gas chromatography, inhibitory effects of chlorinated acetic and propionic acids on gas and acid production by amended anaerobic soil were measured in Landlow clay receiving 0, 10, and 100 ppm monochloroacetic (MCA), dichloroacetic (DCA), trichloroacetic (TCA), and 2,2‐dichloropropionic (DCP, dalapon) acids. The data show that the chlorinated acids inhibited methane production with resultant accumulation of acetate and to a lesser extent propionate. The length of methane inhibition was correlated with chlorinated acid disappearance, varying from a few days for MCA to more than 30 days for TCA and DCP at 100 ppm. In the presence of CaCO3, DCP (100 ppm) was inhibitory for less than 12 days.The data of these experiments indicate that use of the herbicides dalapon and TCA at concentrations approximating normal field rates probably should have no lasting adverse effects on anaerobic systems buffered near neutral pH.

The fermentation of sugar-beet pulp and sucrose in an artificial rumen, and the effect of linseed oil fatty acids on the fermentation.

1. An artificial rumen is described together with associated analytical and sampling procedures.2. The equipment was used to study the effects of linseed oil fatty acids on the fermentation of sugar-beet pulp and of sucrose by rumen micro-organisms.3. With sugar-beet pulp the addition of small amounts of linseed oil fatty acids had little effect on total gas production, utilization of sugar and the molar proportions of steam-volatile acids formed, but they strongly inhibited methane production, whereas large amounts of the fatty acids temporarily inhibited the production of gas and utilization of sugar.4. With sucrose even the smaller amounts of fatty acids had a marked inhibitory effect on the production of gas and utilization of sugar.5. The technique is assessed critically and the results are discussed in the light of previous experiments in vivo.

The effect of oxygen on fermentation of sucrose by rumen micro-organisms in vitro.

1. The effect of oxygen on the fermentation of sucrose by mixed rumen micro-organisms in vitro was studied by adding oxygen to the gas phase in three ways: at the beginning of incubation, at two hourly intervals during incubation and continuously.2. The additions of oxygen had no measurable effect on the utilization of sucrose or on the production of carbon dioxide, steam-volatile acids and particulate organic matter by the micro-organisms. The addition of oxygen at the beginning of incubation inhibited methane production and increased the accumulation of hydrogen. Similar but much less pronounced changes occurred when the oxygen was infused continuously.3. In all the experiments there was a net uptake of oxygen by micro-organisms. When large amounts of oxygen were present in the gas phase the rates of uptake were proportional to these amounts. When small amounts of oxygen were added, the rates of uptake were independent of the amount added and had a value of approximately 5 ml/h when 100 ml of strained rumen contents were incubated.

The effect of C 18 unsaturated fatty acids on methane production in vitro by mixed rumen bacteria

1. 1. Cig unsaturated fatty acids inhibit methane production from various substrates by mixed rumen bacteria in vitro. 2. 2. This inhibition is not due to a competition for available hydrogen, but to a toxic effect towards methanogenic bacteria. 3. 3. Cis-unsaturated fatty acids are much more active than trans isomers or saturated fatty acids. With cis isomers, toxicity increased with the number of double bonds. Various esters were inactive, indicating the importance of the free carboxyl group. 4. 4. These findings can be explained by assuming a physicochemical mechanism of inhibition. 5. 5. With pyruvate as substrate, inhibition of methane production is accompanied by stimulation of propionic acid production. 6. 6. These results, obtained in vitro, can explain and relate recent and earlier observations in vivo.