• Asian-Australasian Journal of Animal Sciences
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• v.24 no.2
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• pp.285-294
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• 2011

The abatement of methane emission from ruminants is an important global issue due to its contribution to greenhouse gas with carbon dioxide. Methane is generated in the rumen by methanogens (archaea) that utilize metabolic hydrogen ($H_2$) to reduce carbon dioxide, and is a significant electron sink in the rumen ecosystem. Therefore, the competition for hydrogen used for methanogenesis with alternative reductions of rumen microbes should be an effective option to reduce rumen methanogenesis. Some methanogens parasitically survive on the surface of ciliate protozoa, so that defaunation or decrease in protozoa number might contribute to abate methanogenesis. The most important issue for mitigation of rumen methanogenesis with manipulators is to secure safety for animals and their products and the environment. In this respect, prophylactic effects of probiotics, prebiotics and miscellaneous compounds to mitigate rumen methanogenesis have been developed instead of antibiotics, ionophores such as monensin, and lasalocid in Japan. Nitrate suppresses rumen methanogenesis by its reducing reaction in the rumen. However, excess intake of nitrate causes intoxication due to nitrite accumulation, which induces methemoglobinemia. The nitrite accumulation is attributed to a relatively higher rate of nitrate reduction to nitrite than nitrite to ammonia via nitroxyl and hydroxylamine. The in vitro and in vivo trials have been conducted to clarify the prophylactic effects of L-cysteine, some strains of lactic acid bacteria and yeast and/or ${\beta}$1-4 galactooligosaccharide on nitrate-nitrite intoxication and methanogenesis. The administration of nitrate with ${\beta}$1-4 galacto-oligosaccharide, Candida kefyr, and Lactococcus lactis subsp. lactis were suggested to possibly control rumen methanogenesis and prevent nitrite formation in the rumen. For prebiotics, nisin which is a bacteriocin produced by Lactococcus lactis subsp. lactis has been demonstrated to abate rumen methanogenesis in the same manner as monensin. A protein resistant anti-microbe (PRA) has been isolated from Lactobacillus plantarum as a manipulator to mitigate rumen methanogenesis. Recently, hydrogen peroxide was identified as a part of the manipulating effect of PRA on rumen methanogenesis. The suppressing effects of secondary metabolites from plants such as saponin and tannin on rumen methanogenesis have been examined. Especially, yucca schidigera extract, sarsaponin (steroidal glycosides), can suppress rumen methanogenesis thereby improving protein utilization efficiency. The cashew nutshell liquid (CNSL), or cashew shell oil, which is a natural resin found in the honeycomb structure of the cashew nutshell has been found to mitigate rumen methanogenesis. In an attempt to seek manipulators in the section on methane belching from ruminants, the arrangement of an inventory of mitigation technologies available for the Clean Development Mechanism (CDM) and Joint Implementation (JI) in the Kyoto mechanism has been advancing to target ruminant livestock in Asian and Pacific regions.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.10
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• pp.839-844
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• 2009

This research investigates the importance of the microbial metabolic pathways such as denitrification, iron reduction, and methanogenesis, in the degradation of organic matters of the sediments. There are statistically significant differences( P < 0.05) in the rates of denitrification, iron reduction, and methanogenesis according to the location: Site A has no plant, Site B is dominated by Scirpus, and Site C is dominated by Phragmites. Among them, Site C showed different methanogenesis rate depending on the sediments depth. The organic matter content increased from Site A to Site C. Site A had the smallest organic matter content whereas it showed the largest denitrification rate and iron reduction rate. Site C had the largest methanogenesis rate. Denitrification is the dominant pathways based on the assumption that anaerobic degradation of organic matter is mainly carried out through denitrification, iron reduction, and methanogenesis.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.8
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• pp.1088-1097
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• 2014

The study aimed to investigate the effects of gynosaponin on in vitro methanogenesis under different forage-concentrate ratios (F:C ratios). Experiment was conducted with two kinds of F:C ratios (F:C = 7:3 and F:C = 3:7) and gynosaponin addition (0 mg and 16 mg) in a $2{\times}2$ double factorial design. In the presence of gynosaponin, methane production and acetate concentration were significantly decreased, whereas concentration of propionate tended to be increased resulting in a significant reduction (p<0.05) of acetate:propionate ratio (A:P ratio), in high-forage substrate. Gynosaponin treatment increased (p<0.05) the butyrate concentration in both F:C ratios. Denaturing gradient gel electrophoresis (DGGE) analysis showed there was no apparent shift in the composition of total bacteria, protozoa and methanogens after treated by gynosaponin under both F:C ratios. The real-time polymerase chain reaction (PCR) analysis indicated that variable F:C ratios significantly affected the abundances of Fibrobacter succinogenes, Rumninococcus flavefaciens, total fungi and counts of protozoa (p<0.05), but did not affect the mcrA gene copies of methanogens and abundance of total bacteria. Counts of protozoa and abundance of F.succinogenes were decreased significantly (p<0.05), whereas mcrA gene copies of methanogens were decreased slightly (p<0.10) in high-forage substrate after treated by gynosaponin. However, gynosaponin treatment under high-concentrate level did not affect the methanogenesis, fermentation characteristics and tested microbes. Accordingly, overall results suggested that gynosaponin supplementation reduced the in vitro methanogenesis and improved rumen fermentation under highforage condition by changing the abundances of related rumen microbes.

• Korean Journal of Environmental Agriculture
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• v.40 no.4
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• pp.295-312
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• 2021

BACKGROUND: Global warming is one of the most pressing environmental issues which concomitantly complicates global climate change. Methane emission is a balance between methanogenesis and methane consumption, both of which are driven by microbial actions in different ecosystems producing methane, one of the major greenhouse gases. Paddy fields are major sources of anthropogenic methane emissions and could be compounded by organic fertilization. METHODS AND RESULTS: Literature reviews were conducted to give an overview of the global warming conditions and to present the relationship of carbon and methane to greenhouse gas emissions, and the need to understand the underlying processes of methane emission. A more extensive review was done from studies on methane emission in paddy fields under organic fertilization with greater emphasis on long term amendments. Changes in paddy soils due to organic fertilization include alterations of the physicochemical properties and changes in biological components. There are diverse phylogenetic groups of methanogens and methane oxidizing bacteria involved in methane emission. Also, multiple factors influence methanogenesis and methane oxidation in rice paddy fields under organic fertilization and they should be greatly considered when developing mitigating steps in methane emission in paddy fields especially under long term organic fertilization. CONCLUSION(S): This review showed that organic fertilization, particularly for long term management practices, influenced both physicochemical and biological components of the paddy fields which could ultimately affect methanogenesis, methane oxidation, and methane emission. Understanding interrelated factors affecting methane emission helps create ways to mitigate their impact on global warming and climate change.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1174-1179
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• 2005

Up-flow sludge blanket(USB) reactors were used to investigate the effects of N/C(${NO_3}^--N/COD$) ratio on simultaneous denitrification and methanogenesis processes. Without nitrate feeding, 84% of the influent COD was converted into methane. With the increase of N/C ratio, nitrogen gas increased while methane production decreased and stopped finally at the N/C ratio over 0.20. Influent nitrate was completely denitrified into nitrogen gas while nitrate removal efficiency dropped below 40% at N/C ratio of 0.40 because of deficiency in organic carbon. Fraction of COD utilized by denitrification increased at higher N/C ratios. Methanogenesis started to be effected at N/C ratio of 0.05, which could explain the competition for organic carbon between these microorganisms such as denitrifiers and methanogens, rather than inhibitory effect of nitrate and its intermediates. Critical N/C ratio for simultaneous denitrification and methanogenesis was found to be 0.20. Influent COD was removed over 92% by denitrification, methanogenesis and other biochemical reactions including cell growth at these N/C ratios.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.9
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• pp.1289-1294
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• 2013

This study evaluated the in vitro effect of medicinal plant extracts on ruminal methanogenesis, four different groups of methanogens and ruminal fermentation characteristics. A fistulated Holstein cow was used as a donor of rumen fluid. Licorice and mugwort extracts (Glycyrrhiza uralensis and Artemisia capillaris, 0.5% and 1% of total substrate DM, respectively), previously used as folk remedies, were added to an in vitro fermentation incubated with buffered-rumen fluid. Total gas production in Glycyrrhiza uralensis extract treatment was not significantly different between treatments (p<0.05) while total gas production in the Artemisia capillaris extract treatment was lower than that of the control. Artemisia capillaris extract and Glycyrrhiza uralensis extract reduced $CH_4$ emission by 14% (p<0.05) and 8% (p<0.05), respectively. Ciliate-associated methanogens population decreased by 18% in the medicinal plant extracts treatments. Medicinal plant extracts also affected the order Methanobacteriales community. Methanobacteriales diversity decreased by 35% in the Glycyrrhiza uralensis extract treatment and 30% in the Artemisia capillaris extract treatment. The order Methanomicrobiales population decreased by 50% in the 0.5% of Glycyrrhiza uralensis extract treatment. These findings demonstrate that medicinal plant extracts have the potential to inhibit in vitro ruminal methanogenesis.

• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.54-61
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• 2001

Changes in methanogenic pathway at low temperature were studied by incubation experiments of sediment slurries from the littoral zone of Reservoir Paldang. Methane production rates in sediment slurries increased exponentially between $5＾{\circ}C$and $45＾{\circ}C$, reached a maximum rate of $7.4\;nmol\;{\cdot}\;g^{-1}\;{\cdot}\;h^{-1}$ at $45＾{\circ}C$, and then declined to low rate. The shift of incubation temperature from high temperature ($30＾{\circ}C$) to lowtemperature ($15＾{\circ}C$) resulted in a decrease of methane production rate and of hydrogen accumulation rate, and the transient accumulation of acetate concentration. Chlorofarm inhibited perfectly methanogenesis and resulted in the accumulation of hydrogen and acetate as immediate precursors for metltane formation at both incubation temperatures of $15＾{\circ}C$ and $30＾{\circ}C$. In terms of equivalent methane which was calculated from the two intermediary metabolites accumulated in absence of methanogenesis, methane production from acetate was accounted for 14% of total methanogenesis at $30＾{\circ}C$ and 75% at $15＾{\circ}C$, respectively. When the high acetate concentrations above 19 mM were added to sediment slurries, methane production was inhibited at the low temperature ($15＾{\circ}C$) . Our results demonstrate that contribution of acetate on methanogenesis increases at low temperature, but this pathway is inhibited by high concentration of acetate. Therefore acetate-utilizing methanogensis appears to be a key reaction at low temperature, and seems to be one of bottlenecks of the low temperature anaerobic degradation of organic matter in littoral sediments of the reservoir.

• Korean Journal of Environmental Agriculture
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• v.33 no.4
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• pp.282-289
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• 2014

BACKGROUND: Methane($CH_4$) is considered as the secondmost potent greenhouse gas after carbon dioxide ($CO_2$). Methanogenesis is an enzyme-mediated multi-step process by methanogens. In the penultimate step, methylated Co-M is reduced by methyl Co-M reductase (MCR) to $CH_4$ involving a nickel-containing cofactor F430. The activity of MCR enzyme is dependent on the F430 and therefore, the bioavailability of Ni to methanogens is expected to influence MCR activity and $CH_4$ production in soil. In this study, different doses of EDTA(Ethylene Diamine Tetraacetic Acid) were applied in flooded soils to evaluate their suppression effect on methane production by chelating Ni of methanogenesis cofactor. METHODS AND RESULTS: EDTA was selected as chelating agents and added into wetland and rice paddy soil at the rates of 0, 25, 50, 75, and $100mmol\;kg^{-1}$ before 4-weeks incubation test. During the incubation, cumulative $CH_4$ production patterns were characterized. At the end of the experiment, soil samples were removed from their jars to analyze total soil Ni and water-soluble Ni content and methanogen abundance. Methane production from 100 mmol application decreased by 55 and 78% in both soils compared to that from 0 mmol. With increasing application rate of EDTA in both soils, water-soluble Ni concentration significantly increased, but total soil Ni and methanogen activities showed negative relationship during incubation test. CONCLUSION: The decrease in methane production with EDTA application was caused by chelating Ni of coenzyme F430 and inhibiting methanogenesis by methyl coenzyme M reductase. Consequently, EDTA application decreased uptake of Ni into methanogen, subsequently inhibited methanogen activities and reduced methane production in flooded soils.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.1
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• pp.73-79
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• 2004

The objective of the present study was to determine whether ${\beta}$1-4 galacto-oligosaccharides (GOS) and Candida kefyr combined with nitrate as manipulators could suppress rumen methanogenesis without nitrate poisoning in sheep. Four rumen fistulated wethers were allocated to a $4{\times}4$ Latin square design. Nitrate (1.3 g $NaNO_3$ $Kg^{-0.75}$body weight) with and without GOS and Candida kefyr were administered into the rumen through fistula as a single dose 30 min after the morning meal. GOS and Candida kefyr were supplemented by sprinkling onto the feed and through rumen fistula, respectively. The four treatments consisted of saline, nitrate, nitrate plus GOS and nitrate plus GOS plus Candida kefyr. Physiological saline was used as the control treatment. Compared to saline treatment, the administration of nitrate alone resulted in a very marked decrease in rumen methanogenesis and an increase in rumen and plasma nitrite production and blood methaemoglobin formation consequently causing a decline in oxygen consumption, carbon dioxide production and metabolic rate. When compared to nitrate alone, the simultaneous administration of nitrate with GOS decreased nitrite accumulation in rumen and plasma and nitrate-induced methaemoglobin, while retaining low methane production. However, GOS could not fully restore metabolic parameters reduced by nitrate. When compared to the simultaneous administration of nitrate with GOS, the simultaneous administration of nitrate with GOS plus Candida kefyr lowered rumen methanogenesis to a negligible level, but did not decrease rumen and plasma nitrite accumulation as well as blood methaemoglobin formation. Thus, these results suggest that combination of nitrate with GOS may be a potent manipulator to suppress rumen methanogenesis with abating the hazards of nitratenitrite toxicity in ruminants.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.739-745
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• 2005

Simultaneous denitrification and methanogenesis at various influent COD/Nitrate-N(below C/N) ratio was investigated with two different anaerobic sludges of which one was inoculated with glucose only and the other was inoculated with glucose and nitrate. Three different C/N ratios of 30, 20, and 10 were applied with each anaerobic sludge in serum bottles agitated in a rotary shaker to monitor the time related changes of amount of gas production and gas composition. Glucose was used as a single carbon source, which was adjusted to 1,000 mg/L as COD and potassium nitrate was used as a nitrogen source to adjust the each C/N ratio. COD removal by methanogenesis was dominant at higher C/N ratios, while COD removal by denitrification was dominant at lower C/N ratios. With the sludges cultured at C/N ratios below 10, SMA and SDNR rising different carbon substrates were investigated. The most efficient carbon substrate was acetate and the highest SMA and SDNR were 0.76 g COD/g VSS day with pure anaerobic sludge and 1.38 g ${NO_3}^--N/g$ VSS day with sludge cultured at C/N ratio of 5, respectively.