CH4 Consumption Rates Research Articles

Investigating the explosive characteristics of hydrogen/ n-butane blended fuel: Experimental and kinetic insights

Investigating the explosive characteristics of H2/n-C4H10 mixtures is crucial for the safe utilization of this blended fuel. Our study focused on varying equivalent ratios and hydrogen blending ratios within a closed 20-L spherical explosion vessel. Additionally, the microscopic kinetics of the reactions were analyzed through chemical reaction simulation. Our findings indicate that the most violent explosion occurred at an equivalent ratio of 1.2. Increasing hydrogen content intensified combustion reactions, reducing flame thickness and inducing cellular structures along the flame front. This escalation also increased explosion pressure, flame temperature, and flame propagation speed, elevating explosion risk. Moreover, the equilibrium molar fraction of O2 and CO2 decreased while that of H2O increased with higher hydrogen blending ratios. Correspondingly, the heat release rate and generation rates of H•, O•, and OH• radicals increased. Notably, the peak time of C2H4 and CH4 consumption rates preceded. Additionally, R5: O2 + H• = O• + OH• and R978: C4H10 + H• = SC4H9 + H2 represented crucial promoting and inhibiting steps, respectively. These insights deepen our understanding of the explosion mechanism of H2/n-C4H10 mixtures, providing a theoretical basis for designing safer protective measures and evaluating explosion risks in industrial production.

Methanol excretion by Methylomonas methanica is induced by the supernatant of a methanotrophic consortium

AbstractBACKGROUNDMethanotrophs play an important role in mitigating methane (CH4) emissions in ecosystems. They closely interact with other microorganisms forming communities where the cross‐feeding of metabolites, presumably methanol (MeOH), is essential for the growth and activity of non‐methanotrophs. The experiments in this study were focused on investigating the effect of adding the supernatant from a methanotrophic consortium to pure cultures of Methylomonas methanica.RESULTSMethanol dehydrogenase inhibition caused the accumulation of MeOH, which resulted in a significant production after 3 h, with 1.99 mmol L−1 CH3OH. The addition of the supernatant was associated with the excretion of MeOH by M. methanica and enhancement of the CH4 consumption rate, despite a reduction in growth. The maximum MeOH concentrations were between 0.7 and 1.5 mmol L−1 CH3OH.CONCLUSIONThese findings indicate that MeOH excretion may indeed be linked to a metabolic imbalance, which could potentially be compensated through the cross‐feeding of metabolites within the methanotrophic community. © 2024 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Catalytic performance of NixCoy catalysts supported on honeycomb-lantern-like CeO2 for dry reforming of methane: Synergistic effect and kinetic study

Dry reforming of methane (DRM) is considered one of the most efficient methods for carbon utilization, as it can transform greenhouse gases (CH4 and CO2) into syngas (CO and H2) which could be widely used in the production of high-value hydrocarbons. The synergistic effect between Ni and Co is leveraged to enhance the coke resistance and stability of Ni-based catalyst during the DRM process, building upon the surface spatial confinement provided by honeycomb-lantern-like CeO2 support. The enhanced catalytic performance of Ni0.9Co0.1 catalyst can be attributed primarily to the addition of cobalt, which facilitates CO2 adsorption and activation, further promotes the Boudouard reaction and aids in the elimination of coke. This phenomenon is supported by evidence from CO2-TPD, XPS, SEM, TGA, XRD, and CO2-TPO analyses. Furthermore, the kinetics of Ni0.9Co0.1 are examined using Power-Law (PL) and Langmuir-Hinshelwood (LH) mechanisms, obtaining the explicit equations for the rate constants (k and kr), reaction orders of the reactants (α and β), and adsorption equilibrium constants (KCH4 and KCO2). The comparison of the predicted CH4 consumption rates with the experimental rates suggests that the LH mechanism is notably more precise than PL mechanism for Ni0.9Co0.1 catalyst. Moreover, the relevant kinetic parameters (the activation energy and pre-exponential factor), pertinent to coke gasification process for the spent Ni0.9Co0.1 and Ni1.0, are determined and calculated through CO2-TPO characterization and the modified Wigner-Polanyi equation.

Diluted methane mitigation by a co-culture of alkaliphilic methanotrophs and the microalgae Scenedesmus obtusiusculus towards carbon neutrality

A co-culture of an alkaliphilic methanotrophic consortium and the microalga Scenedesmus obtusiusculus was designed to consume CH4 and CO2 from diluted CH4 streams under alkaline conditions to favor CO2 retention. The highest CH4 consumption rate in batch assays was 318 mgCH4 gbiomass−1 d−1 with 8 % initial CH4 and nitrate as the nitrogen source. Subsequently, the co-culture was evaluated in a photobioreactor with batch and fed-batch CH4 feeds. Under continuous illumination, the CH4 consumption rate reached 258 mgCH4 gbiomass−1 d−1, but the pH increased to 9.8. After a photonic pH control implementation, the pH remained at 9.1 ± 0.05 with a consumption rate of 196 mgCH4 gbiomass−1 d−1. The co-culture exhibited continuous activity, synchronized growth, and long-term stability, effectively removing both gases in a single reactor. Moreover, the co-culture's biomass showed an increase in reserve molecules, including carbohydrates and lipids, with protein as the primary product (40–52 % DCW), offering potential as a microbial protein source. The photonic pH control exhibited a rapid response, substituting the traditional acid/alkali addition method, which increases salinity, medium volume, and operational costs. The methanotroph-microalgae co-culture is a successful, robust, and stable alternative for diluted methane mitigation, resulting in nearly zero carbon emissions and valuable biomass production.

Experimental erosion of microbial diversity decreases soil CH4 consumption rates.

Biodiversity-ecosystem functioning (BEF) experiments have predominantly focused on communities of higher organisms, in particular plants, with comparably little known to date about the relevance of biodiversity for microbially driven biogeochemical processes. Methanotrophic bacteria play a key role in Earth's methane (CH4 ) cycle by removing atmospheric CH4 and reducing emissions from methanogenesis in wetlands and landfills. Here, we used a dilution-to-extinction approach to simulate diversity loss in a methanotrophic landfill cover soil community. Replicate samples were diluted 101 -107 -fold, preincubated under a high CH4 atmosphere for microbial communities to recover to comparable size, and then incubated for 86 days at constant or diurnally cycling temperature. We hypothesize that (1) CH4 consumption decreases as methanotrophic diversity is lost, and (2) this effect is more pronounced under variable temperatures. Net CH4 consumption was determined by gas chromatography. Microbial community composition was determined by DNA extraction and sequencing of amplicons specific to methanotrophs and bacteria (pmoA and 16S gene fragments). The richness of operational taxonomic units (OTU) of methanotrophic and nonmethanotrophic bacteria decreased approximately linearly with log-dilution. CH4 consumption decreased with the number of OTUs lost, independent of community size. These effects were independent of temperature cycling. The diversity effects we found occured in relatively diverse communities, challenging the notion of high functional redundancy mediating high resistance to diversity erosion in natural microbial systems. The effects also resemble the ones for higher organisms, suggesting that BEF relationships are universal across taxa and spatial scales.

Differential influence of legume and cereal crop residue incorporation on methane production and consumption in a tropical vertisol

Crop residue incorporation to the soil is an essential strategy to improve soil quality and crop productivity in order to attain sustainable development goals. Experiments were conducted to evaluate the differential effect of crop residues on CH4 production and consumption in a tropical vertisol. Soils were incubated with residues of cereals (maize and wheat) and legumes (chickpea and soybean) at 1% w/w, under non-flooded and flooded conditions to estimate CH4 consumption and CH4 production rates, respectively. Rates of CH4 production (ng CH4 produced g/soil/day) varied from 0.068 to 0.107 with lowest in chickpea residue and highest in wheat straw amended soil. CH4 consumption rates (ng CH4 consumed g/soil/day) was highest (0.79) in wheat straw amended soil and lowest (0.53) in chickpea residue amended soil. Organic carbon (%) and available NO3− (mM) contents increased significantly (P > 0.05) in residue amended soils over control under both flooded (methanogenic) and non-flooded (methane consuming) conditions. Abundance of methanogens and methanotrophs was estimated as mcr and pmoA gene copies g−1 soil, indicated that both the microbial groups were stimulated significantly due to the amendment of crop residues. Linear models exhibited significant correlation among CH4 production and consumption with organic carbon, available nitrate and microbial abundance. The study highlights that crop residues incorporation influences both CH4 consumption and production potential of soil and this effect is more pronounced with biomass of cereals than legumes.

Long-term effect of acetate and biochar addition on enrichment and activity of denitrifying anaerobic methane oxidation microbes

The denitrifying anaerobic methane oxidation (DAMO) process plays a crucial role in the global carbon/nitrogen cycles and methane emission control, and also has application potential in biological wastewater treatment. However, given that DAMO microbes are susceptible to external conditions such as additional carbon source in the system, it is essential to evaluate the effect of alternative carbon substance on the enrichment efficiency and metabolic activity of DAMO microbes. To this end, this study investigated the effect of acetate (0.1 mmol/L-R2, 0.5 mmol/L-R3) and biochar addition (R4) on the enrichment and activity of DAMO microbes. The long-term operation showed that the NO2−-N and CH4 consumption rates in the reactors almost presented the sequence of R4>R2>R3>R1. However, the short-term activity test with isotope labelling showed the sequence of R2>R4>R1>R3. Furthermore, the addition of acetate and biochar improved the electrochemical activity and extracellular polymeric substance (EPS) secretion in the systems. In R4 reactor, the proportion of DAMO bacteria was the highest (7.20%), indicating that the addition of biochar could promote the enrichment of DAMO bacteria, and Thauera was co-enriched with the proportion increasing from 0.26% to 6.73%. While in R1, R2 and R3 reactors, DAMO bacteria were enriched with relatively low abundances (0.10%, 0.23%, 0.15%, respectively), together with methanogens and denitrifiers. This study showed that biochar and acetate with appropriate concentration could enhance the enrichment and activity of DAMO bacteria, the results can provide reference for the enrichment of DAMO microbes and its application in the biological nitrogen removal of wastewater.

Methane consumption under the influence of different nitrogen sources in a tropical soil ecosystem

In order to minimize methane (CH4) concentration in the atmosphere we need to better understand CH4 consumption in agricultural soils. Nitrogen application to agriculture is predicted to increase significantly in the coming years to meet food security needs. However, the interaction between soil nitrogen and CH4 consumption is poorly understood. Experiments were carried out to evaluate CH4 consumption under the influence of the three nitrogen sources comprising N2(at ambient+5% and ambient+10%),NO3-N (at 10 mM and 20 mM) and NH4-N (at 10 mM and 20 mM). CH4 consumption was evaluated at different CH4 concentrations and feeding cycles to validate the effect of nitrogen. Among different N sources, N2 stimulated CH4 consumption potential by about 1.11–1.71 times over that in the absence of additional nitrogen (control), while N in the form of both NO3 and NH4 inhibited CH4 consumption by 1.14–2.18 times than in the control. CH4 consumption rate increased with CH4 feeding cycles. The effect of N sources on CH4 consumption followed similar trends irrespective of the N rate added.N2 stimulated the abundance of both nifH and pmoA genes. Abundance of methanotrophs pmoA gene copies and nitrifiers amoA gene copies were more in NH4-Namended soil than NO3-N.Available NO3 content in soil increased 9–30% with CH4 driven N2 fixation. This study concludes that N2 stimulated CH4 consumption while nitrogen in the form of NO3 and NH4 inhibited CH4 consumption in a tropical vertisol.

Diffusion and transformation of methane within the soil profile and surface uptake in dryland spring maize fields under different fertilizer application depths

It is important to assess the potential uptake of methane (CH4) in dryland farming and its contribution to global warming mitigation by elucidating the migration characteristics of CH4 in the soil profile. Therefore, before planting spring maize in the Loess Plateau region of China in 2019–2020, we applied fertilizer at soil depths of 5, 15, 25, and 35 cm (D5, D15, D25, and D35, respectively). The uptake of CH4 and diffusion flux were determined simultaneously in the soil surface and profile. We found that the dryland soil was a sink for CH4 and the cumulative CH4 uptake amount by soil without fertilization during the maize growth stage was 1.54 kg ha–1. Fertilization inhibited the uptake of CH4 by the soil, but deep fertilization promoted its uptake. The cumulative surface CH4 uptake amounts under D15, D25, and D35 were significantly higher than that under D5, i.e., by 42.4%, 105.6%, and 169.1%, respectively. The CH4 concentration and diffusion flux decreased as the soil depth increased, and CH4 diffused downward in the soil profile. The CH4 consumption rate was greater than the production rate in the 0–20 cm soil layer, whereas the opposite was found in the 20–30 cm layer. The surface CH4 uptake flux was significantly positively correlated with the diffusion flux in the 0–30 cm soil layer. Inorganic nitrogen (N) inhibited the diffusion of CH4 from the surface through the soil profile and its diffusion within the profile. The highest maize yield and biomass were obtained under D25. Therefore, increasing the fertilization depth can promote the uptake of CH4 by the soil in maize fields to alleviate climate change, and a fertilization depth of 25 cm is suitable for balancing the requirements for environmental protection and agricultural production. Our findings provide important insights into the production, consumption, diffusion, and uptake of CH4 in dryland farming areas.

Variation in CO2 and CH4 fluxes among land cover types in heterogeneous Arctic tundra in northeastern Siberia

Abstract. Arctic tundra is facing unprecedented warming, resulting in shifts in the vegetation, thaw regimes, and potentially in the ecosystem–atmosphere exchange of carbon (C). However, the estimates of regional carbon dioxide (CO2) and methane (CH4) budgets are highly uncertain. We measured CO2 and CH4 fluxes, vegetation composition and leaf area index (LAI), thaw depth, and soil wetness in Tiksi (71∘ N, 128∘ E), a heterogeneous site located within the prostrate dwarf-shrub tundra zone in northeastern Siberia. Using the closed chamber method, we determined the net ecosystem exchange (NEE) of CO2, ecosystem respiration in the dark (ER), ecosystem gross photosynthesis (Pg), and CH4 flux during the growing season. We applied a previously developed high-spatial-resolution land cover map over an area of 35.8 km2 for spatial extrapolation. Among the land cover types varying from barren to dwarf-shrub tundra and tundra wetlands, the NEE and Pg at the photosynthetically active photon flux density of 800 µmol m−2 h−1 (NEE800 and Pg800) were greatest in the graminoid-dominated habitats, i.e., streamside meadow and fens, with NEE800 and Pg800 of up to −21 (uptake) and 28 mmol m−2 h−1, respectively. Vascular LAI was a robust predictor of both NEE800 and Pg800 and, on a landscape scale, the fens were disproportionately important for the summertime CO2 sequestration. Dry tundra, including the dwarf-shrub and lichen tundra, had smaller CO2 exchange rates. The fens were the largest source of CH4, while the dry mineral soil tundra consumed atmospheric CH4, which on a landscape scale amounted to −9 % of the total CH4 balance during the growing season. The largest seasonal mean CH4 consumption rate of 0.02 mmol m−2 h−1 occurred in sand- and stone-covered barren areas. The high consumption rate agrees with the estimate based on the eddy covariance measurements at the same site. We acknowledge the uncertainty involved in spatial extrapolations due to a small number of replicates per land cover type. This study highlights the need to distinguish different land cover types including the dry tundra habitats to account for their different CO2 and CH4 flux patterns, especially the consumption of atmospheric CH4, when estimating tundra C exchange on a larger spatial scale.

Trimetallic Catalyst Configuration for Syngas Production

AbstractDry reforming of methane (DRM) is a promising catalytic process for syngas production, utilizing and transforming CO2 to higher density compounds in view of circular economy. The performance of a bimetallic NiFe/MgAl2O4 strongly depends on the initial catalyst state – calcined, reduced or CO2‐reoxidized – that corresponds to different structures and is for each state significantly improved by the addition of a low Rh concentration (∼1 wt%). In the bimetallic catalyst, reduction is required to form the most active phase, a Ni3Fe alloy, showing a CH4 consumption rate of 0.9 mol s−1 kgcat−1. For the trimetallic NiFeRh, the effect of the initial state is less pronounced, yielding a CH4 consumption rate of 2.4 mol s−1 kgcat−1 after CO2‐reoxidation. Advanced characterization and modelling were used to gain insights in the trimetallic system and to systematically assess the role of each element. In NiFeRh, reduction leads to the formation of a trimetallic alloy. A subsequent CO2‐reoxidation induces partial Fe segregation from the trimetallic alloy, leading to separate Fe3O4. The latter structure represents the most active state due to the double role that the trimetallic catalyst takes up after H2‐reduction and CO2‐reoxidation: improved activity due to highly dispersed NiRh and NiFe alloy particles and carbon removal due to Fe3O4 particles.

Exploring Methane Emission Drivers in Wetlands: The Cases of Massaciuccoli and Porta Lakes (Northern Tuscany, Italy)

Wetlands are hotspots of CH4 emissions to the atmosphere, mainly sustained by microbial decomposition of organic matter in anoxic sediments. Several knowledge gaps exist on how environmental drivers shape CH4 emissions from these ecosystems, posing challenges in upscaling efforts to estimate global emissions from waterbodies. In this work, CH4 and CO2 diffusive fluxes, along with chemical and isotopic composition of dissolved ionic and gaseous species, were determined from two wetlands of Tuscany (Italy): (i) Porta Lake, a small wetland largely invaded by Phragmites australis reeds experiencing reed die-back syndrome, and (ii) Massaciuccoli Lake, a wide marsh area including open-water basins and channels affected by seawater intrusion and eutrophication. Both wetlands were recognized as net sources of CH4 to the atmosphere. Our data show that the magnitude of CH4 diffusive emission was controlled by CH4 production and consumption rates, being mostly governed by (i) water temperature and availability of labile carbon substrates and (ii) water column depth, wind exposure and dissolved O2 contents, respectively. This evidence suggests that the highest CH4 diffusive fluxes were sustained by reed beds, providing a large availability of organic matter supporting acetoclastic methanogenesis, with relevant implications for global carbon budget and future climate models.

High-Level Squalene Production from Methane Using a Metabolically Engineered Methylomonas sp. DH-1 Strain

Methane is an inexpensive and sustainable raw material with high potential bioconversion into high-value-added compounds. We report the development of a metabolically engineered type I methanotroph, the Methylomonas sp. DH-1 strain, capable of producing squalene from methane. First, a base strain equipped with a Cre-lox-based automated genetic engineering system was constructed in the genome for efficient strain development. Second, the pds-ald-crtN2 gene cluster, which encodes phytoene desaturase, aldehyde dehydrogenase, and diapolycopene oxygenase, was deleted to increase the pool of presqualene diphosphate, an immediate precursor of squalene. Third, the activity of squalene–hopene cyclase was prohibited using ferulenol to concentrate the squalene. Finally, the squalene synthase regulated by a strong promoter was further overexpressed to carry strong flux toward squalene. The final engineered strain produced 8.4 ± 1.2 mg/L of squalene with the content and productivity of 12.0 ± 1.0 mg/g DCW and 58.7 ± 8.5 μg/(L/h), respectively. The fed-batch fermentation of the final engineered strain produced 31.3 mg/L of squalene with the content and productivity of 39.3 mg/g DCW and 746.2 μg/(L/h), respectively, by supplementing KNO3. The final engineered strain exhibited remarkable performance in the bioconversion of methane into squalene with the CH4 consumption rate, yield, and CH4 conversion rate values of 3.09 g/L, 10.2 mg of squalene per gram of methane, and 1.19%, respectively.

Topography-related controls on N2O emission and CH4 uptake in a tropical rainforest catchment

Forest soils in the warm-humid tropics significantly contribute to the regional greenhouse gas (GHG) budgets. However, spatial heterogeneity of GHG fluxes is often overlooked. Here, we present a study of N2O and CH4 fluxes over 1.5 years, along a topographic gradient in a rainforest catchment in Xishuangbanna, SW China. From the upper hillslope to the foot of the hillslope, and further to the flat groundwater discharge zone, we observed a decrease of N2O emission associated with an increase of soil water-filled-pore-space (WFPS), which we tentatively attribute to more complete denitrification to N2 at larger WFPS. In the well-drained soils on the hillslope, denitrification at anaerobic microsites or under transient water-saturation was the potential N2O source. Negative CH4 fluxes across the catchment indicated a net soil CH4 sink. As the oxidation of atmospheric CH4 is diffusion-limited, soil CH4 consumption rates were negatively related to WFPS, reflecting the topographic control. Our observations also suggest that during dry seasons N2O emission was significantly dampened (<10 μg N2O-N m−2 h−1) and CH4 uptake was strongly enhanced (83 μg CH4-C m−2 h−1) relative to wet seasons (17 μg N2O-N m−2 h−1 and 56 μg CH4-C m−2 h−1). In a post-drought period, several rain episodes induced exceptionally high N2O emissions (450 μg N2O-N m−2 h−1) in the groundwater discharge zone, likely driven by flushing of labile organic carbon accumulated during drought. Considering the global warming potential associated with both GHGs, we found that N2O emissions largely offset the C sink contributed by CH4 uptake in soils (more significant in the groundwater discharge zone). Our study illustrates important topographic controls on N2O and CH4 fluxes in forest soils. With projected climate change in the tropics, weather extremes may interact with these controls in regulating forest GHG fluxes, which should be accounted for in future studies.

Do methanotrophs drive phosphorus mineralization in soil ecosystem?

Experiments were carried out to elucidate linkage between methane consumption and mineralization of phosphorous (P) from different P sources. The treatments were (i)no CH4+ no P amendment (absolute control), (ii)with CH4+ no P amendment (control), (iii)with CH4+ inorganic P as Ca3(PO4)2, and (iv)with CH4+ organic P as sodium phytate. P sources were added at 25 µg P·(g soil)-1. Soils were incubated to undergo three repeated CH4 feeding cycles, referred to as feeding cycleI, feeding cycleII, and feeding cycleIII. CH4 consumption rate k (µg CH4 consumed·(g soil)-1·day-1) was 0.297± 0.028 in no P amendment control, 0.457± 0.016 in Ca3(PO4)2, and 0.627± 0.013 in sodium phytate. Rate k was stimulated by 2 to 6 times over CH4 feeding cycles and followed the trend of sodium phytate> Ca3(PO4)2> no P amendment control. CH4 consumption stimulated P solubilization from Ca3(PO4)2 by a factor of 2.86. Acid phosphatase (µg paranitrophenol released·(g soil)-1·h-1) was higher in sodium phytate than the no P amendment control. Abundance of 16SrRNA and pmoA genes increased with CH4 consumption rates. The results of the study suggested that CH4 consumption drives mineralization of unavailable inorganic and organic P sources in the soil ecosystem.

Soil respiration and CH4 consumption covary on the plot scale

Assessing the greenhouse gas (GHG) balance of a landscape or land use can be challenging since greenhouse gas fluxes change over time and can be very different locally. While the spatial variability of carbon dioxide (CO2) fluxes and nitrous oxide (N2O) on the plot scale can hardly be explained, there is first evidence that methane (CH4) consumption covaries with CO2 fluxes in upland forest soils. Yet, if this spatial correlation is persistent over time is unclear. We studied the spatial variability in soil respiration (CO2 fluxes) and soil CH4 consumption in a homogenous, planted forest on an 800 m2 plot. The study was repeated after two weeks at sampling points next to those of the first study. Both studies showed that CH4 consumption was higher at locations with higher soil respiration, and that the correlation between CH4 consumption and soil respiration was persistent between the studies. This result agrees with the interpretation of the rhizosphere as most important source of soil CO2 and potentially preferred habitat for methanotrophic bacteria. The correlation found in the first study allowed predicting CH4 consumption rates of the second study based on the observed CO2 fluxes at the new measurement locations with a standardized root-mean-square error (SRMSE) of 26%. Since soil respiration measurements are much easier to conduct, they would be a good means to complement the more laborious and cost-intensive measurements of CH4 consumption in order to get a more comprehensive estimate of the representative CH4 consumption of a site.

Comparative study of oxygen-limited and methane-limited growth phenotypes of Methylomicrobium buryatense 5GB1

Methylomicrobium buryatense 5 GB1 has been identified as a promising biocatalyst for industrial methane conversion to produce value-added products. However, despite recent advancements in understanding the metabolism of 5 GB1, existing knowledge on the differences between oxygen-limited and methane-limited phenotypes is still limited. In this work, both batch and continuous experiments were carried out to systematically examine the strain’s oxygen-limited and methane-limited phenotypes. Total carbon balances were performed to ensure the obtained measurements of CH4 and O2 consumption rates and CO2 production rate were accurate. Our results showed that the feed gas composition alone does not dictate the strain’s growth phenotype. In order to achieve a desired phenotype, both feed gas composition and cell growth rate have to be controlled. In addition, contrary to the common belief that oxygen-limited conditions lead to increased production of organic compounds, our results suggest that it is the methane-limited condition that has higher yield for organic compounds. Knowledge of these differences could provide key understanding into how M. buryatense 5 GB1 regulate its carbon flow among different pathways under different growth conditions, which will provide the key insights for both mutant design and process design (e.g., culture conditions) for desired outcomes such as increased production of organic acids. Finally, using data collected in this work and those published in literature, we further validated a published genome-scale model under optimal growth condition. In addition, our results suggest that the current model lacks key metabolic routes to explain the surprisingly robust growth exhibited by the strain under wide substrate availability conditions.

Methane consumption potential of soybean-wheat, maize-wheat and maize-gram cropping systems under conventional and no-tillage agriculture in a tropical vertisol

AbstractMethane (CH4) consumption in agricultural soil is imperative for the mitigation of climate change. However, the effect of tillage and cropping systems on CH4consumption is less studied. Experiments were carried out in Madhya Pradesh, India with soybean-wheat (SW), maize-wheat (MW) and maize-gram (MG) cropping systems under conventional tillage (CT) and no-tillage (NT). Soybean/maize was cultivated during thekharifseason (July–October) and wheat/chickpea in therabiseason (October–March) for 9 years consecutively. Soil samples were collected during vegetative growth stages of soybean and maize from different cropping systems. Methane consumption, the abundance of methanotrophs as particulate methane monooxygenase (pmoA) gene copies, soil and crop parameters were estimated. Methane consumption rate was higher in NT and upper soil layer (0–5 cm) than CT and 5–15 cm depth. Methane consumption rate k ranged from 0.35 to 0.56 μg CH4consumed/g soil/d in the order of MW&gt;SW&gt;MG in 0–5 cm. The abundance ofpmoAgene copies ranged from 43 × 104/g soil to 13 × 104/g soil and was highest in MW-NT and lowest in MG-CT. Available nitrogen, phosphorus and potassium were higher in 0–5 cm than in 5–15 cm depth. Soil and plant parameters and abundance ofpmoAgenes correlated significantly and positively with CH4consumption rate. No-tillage stimulated CH4consumption compared to CT irrespective of cropping system and CH4consumption potential was highest in MW and lowest in MG. However, the magnitude of the positive effect of NT towards CH4consumption was higher in SW and MG than MW.

Activity and diversity of methane-oxidizing bacteria along a Norwegian sub-Arctic glacier forefield.

Methane (CH4) is one of the most abundant greenhouse gases in the atmosphere and identification of its sources and sinks is crucial for the reliability of climate model outputs. Although CH4 production and consumption rates have been reported from a broad spectrum of environments, data obtained from glacier forefields are restricted to a few locations. We report the activities of methanotrophic communities and their diversity along a chronosequence in front of a sub-Arctic glacier using high-throughput sequencing and gas flux measurements. CH4 oxidation rates were measured in the field throughout the growing season during three sampling times at eight different sampling points in combination with laboratory incubation experiments. The overall results showed that the methanotrophic community had similar trends of increased CH4 consumption and increased abundance as a function of soil development and time of year. Sequencing results revealed that the methanotrophic community was dominated by a few OTUs and that a short-term increase in CH4 concentration, as performed in the field measurements, altered slightly the relative abundance of the OTUs.

How methane feedback response influence redox processes in a tropical vertisol

It has been predicted that soil CH4 consumption potential will increase due to rise in concentration of atmospheric CH4. However, it is unclear how this altered activity of soil will influence soil biogeochemical processes. Experiments were carried out to examine the effect of CH4 feedback response on (1) CH4 consumption potential, (2) population dynamics of methanotrophs, and (3) reductive biogeochemical processes in a tropical vertisol. Soils of different CH4 consumption potentials were prepared by three CH4 feeding cycles. Soils were then incubated to determine terminal electron accepting process (TEAPs) comprising sequential reduction of terminal electron acceptors (NO3 −, Fe3+, SO4 2−, and CO2). Diversity of methanotrophs was estimated by terminal restriction fragment length polymorphism (TRFLP) targeting the pmoA gene. Methane feedback increased apparent CH4 consumption rate (k) from 0.49 to 1.09 μg CH4 consumed per gram of soil. Potential denitrification rate (PDR), potential iron reduction rate (PIR), potential sulfate reduction rate (PSR) increased with k (p < 0.0001). Abundance of methanotrophs and heterotrophs was positively and significantly correlated with k (p < 0.0001). Methane feedback cycle influenced composition of the methanotrophs community (p < 0.0001). Principal component analysis (PCA) explained 83.86 and 12.05 % of variation by first two components.