Maximum Oxidation Rate Research Articles

Reactor performance and microbial ecology of a nitritation membrane bioreactor

Partial nitritation is an indispensable pretreatment for anaerobic ammonium oxidation process. However, the nitritation is limited by the low growth rates of ammonia-oxidizing bacteria (AOB). In this study, a membrane bioreactor (MBR) was operated for 300 days to assess its nitritation performance and the shift of microbial community. Results showed that the reactor obtained satisfying nitritation after a startup period of 50 days, which finally achieved ammonium conversation rates of about 0.8kgN/m3/d. The apparent half-saturation constant (Km) and maximum ammonium oxidation rate (rmax) of the AOB-enriched culture were determined to be 6.1mgN/L and 1.1kgN/g-VSS/d, respectively. In addition, lower fouling rates were found in the initial operating days that the reactor was fed with lower ammonium loads (day 0–day 150). However, the increased ammonium loads (>0.6kgN/m3/d) in the following 150 days resulted in increases in extracellular polysaccharides, leading to much higher fouling rates. 16S rRNA high-throughput sequencing analysis showed clear changes in the microbial community populations during the MBR operation. Results also showed that ordinary heterotrophic organisms and nitrite-oxidizing bacteria were successively inhibited; finally Nitrosomonas dominated in the nitritation MBR, with relative abundance of 40–46%. Moreover, the AOB-enriched culture was of higher microbial diversity than the seeding sludge. This study could not only improve our understanding of the bacterial community dynamics in nitritation processes, but also provide more alternatives for MBR applications.

Bioregeneration of the pregnant leach solutions obtained during the leaching of nonferrous metals from slag waste by acidophilic microorganisms

The bioregeneration of the solutions obtained after the leaching of copper and zinc from slag waste by sulfuric acid solutions containing ferric iron was examined. For bioregeneration, associations of mesophilic and moderately thermqophilic acidophilic chemolithotrophic microorganisms were made. It has been shown that the complete oxidation of iron ions in solutions is possible at a dilution of the pregnant leach solution with a nutrient medium. It has been found that the maximal rate of oxidation of iron ions is observed at the use of a mesophilic association of microorganisms at a threefold dilution of the pregnant leach solution with a nutrient medium. The application of bioregeneration during the production of nonferrous metals from both copper converter slag and its waste would make it possible to approach the technology of their processing using the closed cycle of workflows.

Effect of training intensity on the fat oxidation rate

Physical exercise is a key modulator of the maximum fat oxidation rate (MFO). However, the metabolic transition zones in the MFO-exercise relationship are not generally considered for training prescription. Objective. To examine the effects of training in different metabolic transition zones on the kinetics of MFO and its localization (Fatmax) in young physically active men. 97 men were divided into 4 similar sized groups, 3 experimental groups and a control group (CG). Subjects in each experimental group undertook an 8-week running program. Training was continuous at the intensity of the aerobic threshold or VT1 (CCVT1); or performed as intervals at the intensity of the anaerobic threshold or VT2 (ITVT2); or at maximum aerobic power VO2max (ITVO2max). Before and after the training intervention, expired gases were monitored in each subject to determine VO2max, VT1, VT2, MFO (by indirect calorimetry) and Fatmax. In response to training, experimental groups showed an increase in MFO (from 16,49 to 18,51%; p<0,01) and a mean reduction in Fatmax of 60,72±10,52 to 52,35±7,61 %VO2max (p<0,01). No changes of interest were observed in the control subjects. Intergroup comparisons revealed no differences in MFO and Fatmax among the experimental groups, though compared to the CG, a greater reduction in Fatmax was observed in CCVT1 (p<0,05). No changes were detected in performance except a drop in VO2max in the GC (p<0,05). 8 weeks of training led to an increase in MFO and reduction in Fatmax irrespective of training intensity.

Bioregeneration of the Solutions Obtained during the Leaching of Nonferrous Metals from Waste Slag by Acidophilic Microorganisms

The bioregeneration of the solutions obtained after the leaching of copper and zinc from waste slag by sulfuric solutions of ferric sulfate is examined. For bioregeneration, associations of mesophilic and moderately thermqophilic acidophilic chemolithotrophic microorganisms were made. It has been shown that the complete oxidation of iron ions in solutions obtained after the leaching of nonferrous metals from waste slag is possible at a dilution of the pregnant solution with a nutrient medium. It has been found that the maximal rate of oxidation of iron ions is observed at the use of a mesophilic association of microorganisms at a threefold dilution of the pregnant solution with a nutrient medium. The application ofbioregeneration during the production of nonferrous metals from both waste and converter slags would make it possible to approach the technology of their processing using the closed cycle of workflows.

Numerical simulation of dynamic processes of the methane migration and oxidation in landfill cover

The coupling model of the multicomponent gas flow and transport was developed to describe methane oxidation in landfill cover. A two‐part simulation was carried out to investigate the dynamic processes of methane oxidation. The reliability of the coupling model was validated by comparing the simulated data on gas concentrations with the measured data. To evaluate the influence of the pumping well on the oxidation reaction, methane emission throughout the landfill cover was simulated. Methane oxidation in the landfill cover demonstrated dynamic characteristics. The results suggest that the oxidation effect is closely related to methane emission. Sensitivity parameters were also introduced to determine the maximum oxidation rate and permeability. The critical targets of the reduction rate and reduction volume of methane were analyzed based on 20 years' worth of pumping operation data. The result further illustrates the dynamic behavior of methane oxidation, which is influenced by the degree of methanotrophic reaction and the balance between methane and air influx in the landfill cover. The results highlight the significance of the study in quantitatively assessing the capacity of landfill covers to reduce methane emissions in landfills. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1419–1424, 2014

Effect of trichloroethylene and tetrachloroethylene on methane oxidation and community structure of methanotrophic consortium

The methane oxidation rate and community structure of a methanotrophic consortium were analyzed to determine the effects of trichloroethylene (TCE) and tetrachloroethylene (PCE) on methane oxidation. The maximum methane oxidation rate (Vmax ) of the consortium was 326.8 μmol·g-dry biomass−1·h−1, and it had a half-saturation constant (Km ) of 143.8 μM. The addition of TCE or PCE resulted in decreased methane oxidation rates, which were decreased from 101.73 to 5.47–24.64 μmol·g-dry biomass−1·h−1 with an increase in the TCE-to-methane ratio, and to 61.95–67.43 μmol·g-dry biomass−1·h−1 with an increase in the PCE-to-methane ratio. TCE and PCE were non-competitive inhibitors for methane oxidation, and their inhibition constants (Ki ) were 33.4 and 132.0 μM, respectively. When the methanotrophic community was analyzed based on pmoA using quantitative real-time PCR (qRT-PCR), the pmoA gene copy numbers were shown to decrease from 7.3 ± 0.7 × 108 to 2.1–5.0 × 107 pmoA gene copy number · g-dry biomass−1 with an increase in the TCE-to-methane ratio and to 2.5–7.0 × 107 pmoA gene copy number · g-dry biomass−1 with an increase in the PCE-to-methane ratio. Community analysis by microarray demonstrated that Methylocystis (type II methanotrophs) were the most abundant in the methanotrophic community composition in the presence of TCE. These results suggest that toxic effects caused by TCE and PCE change not only methane oxidation rates but also the community structure of the methanotrophic consortium.

Investigation of ferrous-iron biooxidation kinetics by Leptospirillum ferriphilum in a novel packed-column bioreactor: Effects of temperature and jarosite accumulation

The kinetics of microbial ferrous-iron by Leptospirillum ferriphilum was studied at substrate loading rate of 3–90mmolL−1h−1 in a novel packed column bioreactor. The study was conducted with a view to providing an understanding of the reaction kinetics in a flow-through system which may be assumed to mimic bioheap solution flow, rather than the more typical batch reactors. The bioreactor was maintained at pH of 1.45±0.05 and constant air flow rate of 15mLs−1. The Boon and Hansford, and the Monod models accurately described the experimental data. The effect of temperature on the kinetic parameters was investigated at 25, 30 and 35°C. The maximum oxidation rate, rFe2+max=15.10mmolL−1h−1, was highest at 35°C. The activation energy, Ea=20.97kJmol−1, of ferrous-iron biooxidation in the novel bioreactor is indicative of a system that is limited by both biochemical and diffusion factors. The result also showed about 38.80% increase in the maximum microbial ferrous-iron oxidation,rFe2+max, due to accumulation of jarosite. However, the decreasing values of substrate affinity constant, KFe2+, and the apparent affinity constant, K′Fe2+ revealed that the microbial affinity for ferrous biooxidation increases with increase in jarosite formation. This study reveals that jarosite maybe beneficial to bioleach heaps if it is carefully managed.

Heavy reliance on carbohydrate across a wide range of exercise intensities during voluntary arm ergometry in persons with paraplegia

Context/objectiveTo describe and compare substrate oxidation and partitioning during voluntary arm ergometry in individuals with paraplegia and non-disabled individuals over a wide range of exercise intensities.DesignCross-sectional study.SettingClinical research facility.ParticipantsTen apparently healthy, sedentary men with paraplegia and seven healthy, non-disabled subjects.InterventionsRest and continuous progressive voluntary arm ergometry between 30 and 80% of peak aerobic capacity (VO2peak).Outcome measuresTotal energy expenditure and whole body rates of fat and carbohydrate oxidation.ResultsA maximal whole body fat oxidation (WBFO) rate of 0.13 ± 0.07 g/minute was reached at 41 ± 9% VO2peak for subjects with paraplegia, although carbohydrate became the predominant fuel source during exercise exceeding an intensity of 30–40% VO2peak. Both the maximal WBFO rate (0.06 ± 0.04 g/minute) and the intensity at which it occurred (13 ± 3% VO2peak) were significantly lower for the non-disabled subjects than those with paraplegia.ConclusionSedentary individuals with paraplegia are more capable of oxidizing fat during voluntary arm ergometry than non-disabled individuals perhaps due to local adaptations of upper body skeletal muscle used for daily locomotion. However, carbohydrate is the predominant fuel source oxidized across a wide range of intensities during voluntary arm ergometry in those with paraplegia, while WBFO is limited and maximally achieved at low exercise intensities compared to that achieved by able-bodied individuals during leg ergometry. These findings may partially explain the diminished rates of fat loss imposed by acute bouts of physical activity in those with paraplegia.

Targeted 13C enrichment of lipid and protein pools in the body reveals circadian changes in oxidative fuel mixture during prolonged fasting: A case study using Japanese quail

Many animals undergo extended periods of fasting. During these fasts, animals oxidize a ratio of macronutrients dependent on the nutritional, energetic, and hydric requirements of the fasting period. In this study, we use Japanese quail (Coturnix coturnix japonica), a bird with natural intermediate fasting periods, to examine macronutrient use during a 6d fast. We raised groups of quail on isotopically labeled materials (13C-1-leucine, 13C-U-glucose, or 13C-1-palmitic acid) with the intent of labeling specific macronutrient/tissue pools in each treatment, and then traced their use as fuels by measuring the δ13C values of breath CO2. Based on changes in δ13C values during the fast, it appears that the carbohydrate label,13C-U-glucose, was largely incorporated into the lipid pool and thus breath samples ultimately reflected lipid use rather than carbohydrate use. In the lipid treatment, the 13C-1-palmitic acid faithfully labeled the lipid pool and was reflected in the kinetics δ13C values in breath CO2 during the fast. Endogenous lipid oxidation peaked after 24h of fasting and remained constantly elevated thereafter. The protein label,13C-1-leucine, showed clear diurnal periods of protein sparing and degradation, with maximal rates of protein oxidation occurring at night and the lowest rates occurring during the day time. This stable isotope tracer method provides a noninvasive approach to study the nutrient dynamics of fasting animals and should provide new insights into how different types of animals use specific nutrient pools during fasting and possibly other non-steady physiological states.

The Use of Carbohydrates During Exercise as an Ergogenic Aid

Carbohydrate and fat are the two primary fuel sources oxidized by skeletal muscle tissue during prolonged (endurance-type) exercise. The relative contribution of these fuel sources largely depends on the exercise intensity and duration, with a greater contribution from carbohydrate as exercise intensity is increased. Consequently, endurance performance and endurance capacity are largely dictated by endogenous carbohydrate availability. As such, improving carbohydrate availability during prolonged exercise through carbohydrate ingestion has dominated the field of sports nutrition research. As a result, it has been well-established that carbohydrate ingestion during prolonged (>2 h) moderate-to-high intensity exercise can significantly improve endurance performance. Although the precise mechanism(s) responsible for the ergogenic effects are still unclear, they are likely related to the sparing of skeletal muscle glycogen, prevention of liver glycogen depletion and subsequent development of hypoglycemia, and/or allowing high rates of carbohydrate oxidation. Currently, for prolonged exercise lasting 2-3 h, athletes are advised to ingest carbohydrates at a rate of 60 g·h⁻¹ (~1.0-1.1 g·min⁻¹) to allow for maximal exogenous glucose oxidation rates. However, well-trained endurance athletes competing longer than 2.5 h can metabolize carbohydrate up to 90 g·h⁻¹ (~1.5-1.8 g·min⁻¹) provided that multiple transportable carbohydrates are ingested (e.g. 1.2 g·min⁻¹ glucose plus 0.6 g·min⁻¹ of fructose). Surprisingly, small amounts of carbohydrate ingestion during exercise may also enhance the performance of shorter (45-60 min), more intense (>75 % peak oxygen uptake; VO(₂peak)) exercise bouts, despite the fact that endogenous carbohydrate stores are unlikely to be limiting. The mechanism(s) responsible for such ergogenic properties of carbohydrate ingestion during short, more intense exercise bouts has been suggested to reside in the central nervous system. Carbohydrate ingestion during exercise also benefits athletes involved in intermittent/team sports. These athletes are advised to follow similar carbohydrate feeding strategies as the endurance athletes, but need to modify exogenous carbohydrate intake based upon the intensity and duration of the game and the available endogenous carbohydrate stores. Ample carbohydrate intake is also important for those athletes who need to compete twice within 24 h, when rapid repletion of endogenous glycogen stores is required to prevent a decline in performance. To support rapid post-exercise glycogen repletion, large amounts of exogenous carbohydrate (1.2 g·kg⁻¹·h⁻¹) should be provided during the acute recovery phase from exhaustive exercise. For those athletes with a lower gastrointestinal threshold for carbohydrate ingestion immediately post-exercise, and/or to support muscle re-conditioning, co-ingesting a small amount of protein (0.2-0.4 g·kg⁻¹·h⁻¹) with less carbohydrate (0.8 g·kg⁻¹·h⁻¹) may provide a feasible option to achieve similar muscle glycogen repletion rates.

Effects of ammonia on methane oxidation in landfill cover materials

The effects of ammonia (NH3) on CH4 attenuation in landfill cover materials consisting of landfill cover soil (LCS) and aged municipal solid waste (AMSW), at different CH4 concentrations, were investigated. The CH4 oxidation capacities of LCS and AMSW were found to be significantly affected by the CH4 concentration. The maximum oxidation rates for LCS and AMSW were obtained at CH4 concentrations of 5% and 20%(v/v), respectively, within 20 days. CH4 biological oxidation in AMSW was significantly inhibited by NH3 at low CH4 concentrations (5%, v/v) but highly stimulated at high levels (20% and 50%, v/v). Oxidation in LCS was stimulated by NH3 at all CH4 concentrations due to the higher conversion of the nitrogen in NH3 in AMSW than in LCS. NH3 increases CH4 oxidation in landfill cover materials.

Landfill CH4 Oxidation, N2O, and CO2 Emissions from Wastewater-Incubated Mineralised Refuse: The Effect of Heavy Metal Addition and Environmental Factor Variations

The first investigations on anthropogenic methane (CH4) oxidation and nitrous oxide (N2O) emissions from mineralised refuse after wastewater treatment are reported. The maximum methane oxidation rate (MOR) in the incubated material was 15.48 μmol/g dry weight/h, which was substantially higher than those for the original mineralised refuse or soil. A correlation analysis (P > 0.05) showed that the mean particle size (D50) value, organic matter content, NH4+–N nitrification, and NO3−–N generation rates (P 0.05). Following the addition of distilled water, N2O emissions from the incubated mineralised refuse were almost two times and 1 order of magnitude greater than those of the MOR (P > 0.05) and soil (P > 0.05). The stimulation of N2O emissions from the mineralised refuse could be neglected under the much higher MOR of a municipal solid waste landfill. Because of its high tolerance for environmental factor variations (i.e., soil temperature and water content) and heavy metal addition, mineralised refuse could be used to filter a wide variety of wastewaters to increase the MOR.

Sirtuin 1-mediated Effects of Exercise and Resveratrol on Mitochondrial Biogenesis

The purpose of this study was to evaluate the role of sirtuin 1 (SirT1) in exercise- and resveratrol (RSV)-induced skeletal muscle mitochondrial biogenesis. Using muscle-specific SirT1-deficient (KO) mice and a cell culture model of differentiated myotubes, we compared the treatment of resveratrol, an activator of SirT1, with that of exercise in inducing mitochondrial biogenesis. These experiments demonstrated that SirT1 plays a modest role in maintaining basal mitochondrial content and a larger role in preserving mitochondrial function. Furthermore, voluntary exercise and RSV treatment induced mitochondrial biogenesis in a SirT1-independent manner. However, when RSV and exercise were combined, a SirT1-dependent synergistic effect was evident, leading to enhanced translocation of PGC-1α and SirT1 to the nucleus and stimulation of mitochondrial biogenesis. Thus, the magnitude of the effect of RSV on muscle mitochondrial biogenesis is reliant on SirT1, as well as the cellular environment, such as that produced by repeated bouts of exercise.

Numerical modeling of nitrogen removal processes in biofilters with simultaneous nitritation and anammox

This study developed a simple numerical model for nitrogen removal in biofilters, which was designed to enhance simultaneous nitritation and anaerobic ammonium oxidation (anammox). It is the first attempt to simulate anammox together with two-step nitrification in natural treatment systems, which may have different kinetic parameters and temperature effects from conventional bioreactors. Prediction accuracy was improved by adjusting kinetic coefficients over the startup period of the biofilters. The maximum rates of nitritation and nitrite oxidation increased linearly over time during the startup period. Simulations confirmed successful enhancement of simultaneous nitritation and anammox (SNA) in the biofilters, with anammox contributing 35% of ammonium removal. Effluent ammonium concentration was affected by influent ammonium concentration and the maximum nitritation rate, and was insensitive to the maximum nitrite oxidation rate and anammox substrate factor. Ammonium removal via SNA was likely limited by biomass of aerobic ammonia oxidizing bacteria in the biofilters. The developed model is a promising tool for studying the dynamics of nitrogen removal processes including SNA in natural treatment systems.

Landfill CH4 oxidation and N2O emissions by aged refuse: Effects of wastewater NH4+-N incubation, heavy metals and pH

We report on preliminary investigations into CH4 oxidation and N2O emissions from aged refuse following wastewater treatment. The maximum CH4 oxidation rate by incubated aged refuse (IAR) was 79.11μmolg−1h−1, which was much higher than that of original aged refuse (OAR). This result can be attributed to effects arising from the retention of suspended solids and organic matter and the growth of ammonia-oxidizing bacteria through wastewater treatment. After distilled water addition, N2O and CO2 emissions from IAR were almost two times higher than those of OAR (p>0.05) and an order of magnitude higher than that of soil (p>0.05). With the heavy metal addition in aged refuse, there was a negligible difference (p<0.05) from the control without heavy metal addition. Due to the higher tolerance to changes in pH and heavy metal concentrations in aged refuse, a wide scope of wastewater could be selected for its pre-incubation.

Lessons Learned Regarding Symptoms of Tryptophan Deficiency and Excess from Animal Requirement Studies ,

Tryptophan is the precursor for several neurotransmitters and metabolic regulators, which, although quantitatively of little importance in determining the dietary requirement, have major importance for interpreting symptoms of dietary tryptophan deficiency and excess. The quantitative dietary tryptophan requirement appears to vary widely across species, so intakes relative to requirements are more appropriate expressions for comparison of adverse effects across species than daily intake or diet concentration. Symptoms of tryptophan deficiency may occur at intakes as little as 25% below the requirement. Symptoms include reduced feed intake and reduced growth rate but also impaired skeletal development and aberrant behavior. Older animals appear less susceptible than younger animals to tryptophan deficiency and females less than males. Symptoms of excess tryptophan intake include reduced food intake and growth rate. In growing animals, it appears that tryptophan intakes of >10 times the requirement are necessary before there are detrimental effects on growth performance. At still greater intakes, fatty liver and fibrotic changes in muscles, lung, and pancreas and the serotonin syndrome may develop. In pigs, tryptophan intake of 60 times the daily requirement did not cause mortality. The maximal tryptophan oxidation rate, measured in vivo using 13C universally labeled tryptophan, may be a possible marker of the intake above which increasing intake increases the risk of adverse effects. The advantage of the oxidation technique is that it does not necessarily rely on but still allows the identification and measurement of amino acid metabolites and is therefore simpler and more universally applicable.

Soot low-temperature combustion on Cu–Zr/ZSM-5 catalysts in O2/He and NO/O2/He atmospheres

Zirconium doped Cu/ZSM-5 catalysts were prepared and characterized in this investigation. Catalytic activity during soot combustion was determined in both O2/He and NO/O2/He atmospheres by temperature-programmed oxidation. The use of zirconium reduces the temperature of maximum soot oxidation rate by 229°C in O2/He atmosphere and 270°C in NO/O2/He atmosphere. The promoting effect of zirconium is discussed in terms of surface dispersion, enrichment of active components, and creation of oxygen vacancies where molecular oxygen or NOx is adsorbed forming basic surface oxygen species active for soot oxidation. The NO2 formed at the copper–zirconium interface sites leads to the ignition temperature being significantly decreased to 93°C, which is inside the exhaust temperature range of diesel engines. To understand the combustion reaction kinetics, the activation energy and reaction order of soot combustion were evaluated. According to the Redhead method, the activation energy for non-catalyzed reaction is 164kJ/mol under the O2/He atmosphere. For the Cu/ZSM-5 and Cu–Zr/ZSM-5, the activation energies under the O2/He atmosphere (134–151kJ/mol) are slightly higher than those under the NO/O2/He atmosphere (128–135kJ/mol). The Freeman–Carroll method is suitable to describe the soot combustion in the NO/O2/He atmosphere, with the activation energies for the catalysts in the range of 97–112kJ/mol and the average value of reaction order equal to 1.36.

Performance of Ce substituted hydrotalcite-derived mixed oxide catalysts Co2.5Mg0.5Al1 − x%Cex%O used for soot combustion and simultaneous NOx-soot removal

The Co2.5Mg0.5Al1−x%Cex%O hydrotalcite-derived catalysts (CMACex) with different Ce/Al atomic ratios were synthesized by co-precipitation, which simultaneously possess multiple properties for soot combustion, lean-burn NOx storage and simultaneous NOx-soot removal. The techniques including XRD, EXAFS, BET, H2-TPR, O2-TPD and in-situ DRIFTS were used for catalyst characterization. It is found that Ce-substituted catalysts are much more active than Ce-free one for soot combustion, NOx storage and simultaneous NOx‐soot removal. Among the catalysts containing Ce, CMACe8 exhibits the highest performance, showing the lowest temperature of 384°C for the maximal soot oxidation rate (Tm), the largest NOx storage capacity (336μmolg−1), and the largest NOx reduction percentage of 15.4%. Compared with Ce-free sample, Ce-substitution increases the specific surface area, the redox properties and the amount of surface lattice oxygen species of the catalyst. The optimal Ce-substitution amount in Co2.5Mg0.5Al1−x%Cex%O is x=8. In-situ DRIFTS results reveal that NO is readily oxidized to NO2 and stored as nitrates over Ce-substituted catalysts, which are very reactive intermediates for simultaneous NOx-soot removal.

Optimization of a horizontal-flow biofilm reactor for the removal of methane at low temperatures

Three pilot-scale, horizontal-flow biofilm reactors (HFBRs 1–3) were used to treat methane (CH4)-contaminated air to assess the potential of this technology to manage emissions from agricultural activities, waste and wastewater treatment facilities, and landfills. The study was conducted over two phases (Phase 1, lasting 90 days and Phase 2, lasting 45 days). The reactors were operated at 10 °C (typical of ambient air and wastewater temperatures in northern Europe), and were simultaneously dosed with CH4-contaminated air and a synthetic wastewater (SWW). The influent loading rates to the reactors were 8.6 g CH4/m3/hr (4.3 g CH4/m2 TPSA/hr; where TPSA is top plan surface area). Despite the low operating temperatures, an overall average removal of 4.63 g CH4/m3/day was observed during Phase 2. The maximum removal efficiency (RE) for the trial was 88%. Potential (maximum) rates of methane oxidation were measured and indicated that biofilm samples taken from various regions in the HFBRs had mostly equal CH4 removal potential. In situ activity rates were dependent on which part of the reactor samples were obtained. The results indicate the potential of the HFBR, a simple and robust technology, to biologically treat CH4 emissions. Implications: The results of this study indicate that the HFBR technology could be effectively applied to the reduction of greenhouse gas emissions from wastewater treatment plants and agricultural facilities at lower temperatures common to northern Europe. This could reduce the carbon footprint of waste treatment and agricultural livestock facilities. Activity tests indicate that methanotrophic communities can be supported at these temperatures. Furthermore, these data can lead to improved reactor design and optimization by allowing conditions to be engineered to allow for improved removal rates, particularly at lower temperatures. The technology is simple to construct and operate, and with some optimization of the liquid phase to improve mass transfer, the HFBR represents a viable, cost-effective solution for these emissions.

Effect of dietary nitrate on skeletal muscle energetics in normoxia and hypoxia

Hypoxia is associated with a reduction in the maximal oxidative metabolic rate of skeletal muscle which is reflected in a slowing of muscle phosphocreatine (PCr) recovery kinetics following exercise. For the same metabolic rate, there is a greater muscle metabolic perturbation (e.g., greater fall in [PCr]) during exercise performed in hypoxia compared to normoxia. Nitric oxide (NO) is a key signalling molecule for hypoxic vasodilatation and it also modulates mitochondrial O2 consumption. Dietary nitrate intake, which increases NO bioavailability, might therefore improve O2 delivery to active muscle and reduce O2 demand during hypoxic exercise. It has been shown that nitrate supplementation lessens muscle metabolic perturbation during high-intensity exercise and considerably enhances exercise tolerance in moderate hypoxia. Nitrate supplementation has also been shown to abolish the reduction in the rate of PCr recovery which is typically observed in hypoxia, indicating enhanced muscle oxygenation and a restoration of muscle oxidative function. Further research is warranted to identify to what extent these effects can be attributed to changes in muscle energy metabolism and/or improved O2 delivery. These findings indicate that dietary nitrate supplementation may have important therapeutic applications for improving skeletal muscle energetics and functional capacity in conditions where muscle O2 delivery is compromised.