Production Rate Constant Research Articles

Exploring optimal environmental factors for fermentative hydrogen production from starch using mixed anaerobic microflora

Our previous work demonstrated that an acclimated mixed bacterial consortium was able to produce H 2 from sugar substrates. To reduce the medium cost for more commercially viable H 2 production, cassava starch was used as the feedstock to produce H 2 via dark fermentation. Three factors, namely, temperature, pH and starch concentration ( C starch ) , were intensively examined for their effects on H 2 production activity. The H 2 production kinetics was determined using a Monod-type kinetic model. The results show that mesophilic temperature ( 37 ∘ C ) is preferable for H 2 production with the H 2 -producing sludge used. The H 2 production efficiency and the composition of soluble metabolites were found to be highly sensitive to the change in pH, as pH 6.0 seemed to give the best overall H 2 production performance. In a non-pH-controlled culture (initial pH = 8.5 ), ethanol and butyrate were the major soluble metabolites, whereas the predominant metabolites switched to butyrate alone (accounting for 70–80% of total soluble microbial products) when the culture pH was controlled at a fixed level ranging from 5.5 to 7.0. Meanwhile, the maximum H 2 production rate occurred when the initial starch concentration was 24 g COD/l. The dependence of H 2 production rate on starch concentration could be described by using Monod-type model and the predicted kinetic constants, namely, maximum H 2 production rate ( v max , H 2 ) and Monod constant ( K s ) , were 1741 ml/h/l and 16.28 g COD/l, respectively. Under the optimal conditions ( 37 ∘ C , pH 6.0, C starch = 24 g COD / l ), the H 2 production rate increased to 1119 ml/h/l, while a high H 2 yield of 9.47 mmol H 2 /g starch was obtained. This performance appeared to be superior to that obtained from other starch-to-bio H 2 systems reported in the literature.

Effect of cultivar and formaldehyde treatment of barley grain on rumen fermentation characteristics using <i>in vitro</i> gas production

The aim of this study was to determine the effects of cultivar and formaldehyde treatment of barley grains on rumen fermentation characteristics using the in vitro gas production technique. Amount of gas produced (mL/g organic matter (OM)) during fermentation was determined after 0, 3, 6, 12, 24, 48, 72 and 96 h of incubation in buffered rumen fluid. The gas production kinetics were described using the equation: y = A {1 – exp [- b (t-T) – c (√t - √T)]} where b and c are the initial gas production rate constant (h-1) and later gas production rate constant (h-1/2), respectively. Cultivar and formaldehyde treatment had significant effects on gas production kinetics. Total gas production (A) ranged from 389.9 to 410.8 (mL/g OM) with the cultivar, Esterel, producing the largest volume of gas of the cultivars. Due to low gas production rates at 3, 6 and 12 h of incubation the cultivars, Viva and Cecilla, took the longest to produce 50% of their total volume of gas. Formaldehyde treatment reduced the rate (μ) of gas production at 3, 6 and 12 h of incubation, and the total volume of gas (A), but increased the time (h) to produce 50% of A and reduced the time (h) to produce 95% of A. The reduction in gas production ranged from 33.3 to 51 mL/g OM with 6 h incubation showing the highest decrease in gas production. It is concluded that formaldehyde treatment may provide an opportunity to manipulate the site of digestion of barley grain in the digestive tract of ruminants. Through the selection of suitable cultivars and through formaldehyde treatment the nutritional and health problems associated with the fermentation of barley grain in the rumen could be reduced. Keywords: Barley cultivars; formaldehyde treatment; gas production kinetics South African Journal of Animal Sciences Vol. 35 (3) 2005: pp.206-212

Effect of heat treatment on <i>in situ</i> rumen degradability and <i>in vitro </i>gas production of full-fat soyabeans and soyabean meal

The objective of this study was to determine the effect of the heat treatment of full-fat soyabean (FFSB) and solvent extracted soyabean meal (SBM) on the in situ dry matter (DM) and protein degradability, and in vitro gas production kinetics of the protein sources. Ruminal disappearance of DM and crude protein (CP), and in vitro gas production were determined after 0, 4, 8, 16, 24, 48 and 72 h incubation using the in situ ruminal degradation and in vitro gas production techniques, respectively. In situ DM and CP disappearances were fitted to the exponential equation p = a + b (1-e-ct), where a is the rapid degradable fraction and b is the slow degradable fraction. In vitro gas production data were fitted to the equation, y = A {1 – exp [- b (t-T) – c (√t - √T)]}. Where b and c are the initial gas production rate constant (h-1) and later gas production rate constant (h-1/2), respectively. The two protein sources were heat treated both with steam pressure in an autoclave at 120 °C and in an oven at 150 °C for 20 min. Heat treatment had a significant effect on effective DM degradability (EDMD), effective CP degradability (ECPD) and in vitro gas production. Although the heat treatments reduced the EDMD, ECPD and the amount of gas produced, the results were inconsistent between protein sources. The heat treatments applied in the autoclave and the oven reduced the ECPD0.02 of FFSB by 12.5% and 10.9%, respectively. On the other hand, heat treatment applied through the autoclave decreased the ECPD0.02 of SBM by 13.9%, but by 18.7% when heat was applied through the oven. Heat treatment of SBM using the oven seemed to be more effective than using autoclaving. Heat treatments in the autoclave and oven reduced the total gas production from FFSB by 7.25 and 7.32%, respectively, and from SBM by 12.69 and 7.91%, respectively. It was concluded that heat treatment is an effective method of altering the rumen degradation characteristics of DM and CP in SBM and FFSB. Both methods could be used to increase the proportion of the rumen non-degradable protein fraction in protein sources which would then reach the small intestines unaffected by ruminal fermentation. Keywords: Full-fat soyabean; soyabean meal; heat treatment; in situ protein degradation; in vitro gas production South African Journal of Animal Sciences Vol. 35 (3) 2005: pp.186-194

Ultra-fine grinding of inorganic powders by stirred ball mill: Effect of process parameters on the particle size distribution of ground products and grinding energy efficiency

A series of wet grinding experiments have been carried out using a stirred ball mill to systematically investigate the effect of processing conditions on the final particle size distribution and grinding kinetics. A sub-micron particle size down to 350 nm was achieved, while the grinding energy efficiency or enhanced grinding rate was shown to be improved with the addition of grinding aids and with the use of smaller grinding media. A simple exponential relation was then proposed to quantitatively describe the observed grinding behavior by introducing the production rate constant,K. It is suggested that by usingK as a guideline, ways of improving the grinding energy efficiency can be established, e.g. use of smaller grinding media, choosing larger particle size class materials, etc.

Microcalorimetric Study on the Toxic Effect of Pb2+ to Tetrahymena

The toxic effect of Pb2+ has been studied in eukaryotic cells by using Tetrahymena as a target. The maximum power (P(m)) and the growth rate constant (k) were determined, which showed that values of P(m) and k were linked to the concentration (C) of Pb2+. The addition of Pb2+ caused a decrease of the maximum heat production and growth rate constant, indicating that Tetrahymena growth was inhibited in the presence of Pb2+, and Pb2+ took part in the metabolism of cells. From micrographs, morphological changes of Tetrahymena were observed with addition of Pb2+, indicating that the toxic effect of Pb2+ derived from destroying the membrane of surface of Tetrahymena. According to the thermogenic curves and photos of Tetrahymena under different conditions, it is clear that metabolic mechanism of Halobacterium halobium R1 growth has been changed with the addition of Pb2+.

Productivity evaluation of hydraulically fractured gas-condensate reservoirs

This study describes an application of a compositional single well simulator to analyse well tests in gas-condensate reservoirs. An important aspect of this application for gas-condensate well tests is accurate fluid property prediction during the multi-phase flow regime, which occurs in the near-well region. The simulator can also be used to understand the impact of liquid drop-out and fracture flow on well productivity. Hydraulic fracturing improves the economics of wells drilled in tight reservoirs. However, the operation involves a significant amount of expenditure. In recent years this technique has also been used to stimulate gas-condensate reservoirs by creating a flow conduit through the condensate banking near the well. Thus, it is crucial to keep a fracture as small as possible. In practice it has been proved that a short, wide fracture can provide much higher production than the traditionally pursued narrow, long fracture. The workflow in this study contains compositional simulation of a single well in a tight gas-condensate reservoir, which is used to generate transient pressure data for well test analysis and interpretation to predict multi-phase flow behaviour, and to analyse productivity impairment due to condensation. Simulation models were then further modified to study the impact of various hydraulic fractures on the well productivity index (PI), which is defined as the ratio of production rate (constant) divided by the pressure drop across the reservoir. PIs for fractured cases are compared with respect to the non-fractured base case. Streamline simulation of the fractured gas-condensate reservoir was also included in the study to allow visualization of the flow profile in and around the hydraulic fracture.

Development of a Culture Sub‐population Induction Model: Signaling Pathways Synergy and Taxanes Production by Taxuscanadensis

Cell cultures of Taxus canadensis were subjected to exogenously applied ethylene (ET) hormone and methyl jasmonate (MJ) elicitation in factorial design experiments. Levels of extracellular taxanes, including paclitaxel, were used with principal component analysis for fault detection and real-coded genetic algorithms for parameter optimization to construct a culture sub-population induction model. Culture sub-populations were identified by the model as (1) uninduced, (2) induced to unilateral function of the ET-signaling pathway, and (3) induced to cooperation between jasmonic acid (JA)- and ET-signaling pathways. Comprehensive model results suggested greater rates of cellular induction (resulting in exogenous taxane production) by ET gas as opposed to MJ elicitation. However, cellular induction of ET-signaling pathway genes increased the rate of induction of JA-signaling pathway genes by orders of magnitude. In addition, model results showed that induction of genes leading to extracellular production of the simple taxane 10-deacetylbaccatin III was regulated by the unilateral ET-signaling pathway. However, it was suggested that further processing of this simple taxane to complex taxane structures, such as paclitaxel, required further gene induction by the JA-signaling pathway. Thus, production rate constants of exogenous complex taxanes were predicted to be an order of magnitude lower than that for the simple taxane 10-deacetylbaccatin III. The fraction of the cell culture sub-population displaying unilateral ET-signaling pathway gene induction was found inversely proportional to levels of MJ elicitation. When coupled with simple non-growth product models, levels of all extracellular taxanes were effectively predicted using the culture sub-population induction model.

Bioreduction of phenylglyoxylic acid to R-(−)-mandelic acid by Saccharomyces cerevisiae FD11b

Screening from 40 microorganisms belonging to different taxonomical groups ( Saccharomyces cerevisiae, Lactoballius, Streptococcus faecalis and Candida albicans) was performed to select the strain with high production rate of R-(−)-mandelic acid (R-MA). A sp. strain S. cerevisiae FD11b with high yield and enantiomeric excess (e.e.) and little byproducts was obtained by means of UV-mutation breeding. In the optimal conditions of pH 6.5, 32 °C, anaerobic and glucose supply rate ( F glu) 0.0833 mmol gdw −1 h −1, the strain FD11b showed a high specific MA production rate ( q p = 0.35 mmol gdw −1 h −1) and enantioselectivity (e.e. = 97.1%). The phenylglyoxylic acid (PGA) concentration showed a remarkable effect on the apparent activity of MA dehydrogenase. The specific production rate ( q p) reached the maximum at 30–40 mM of PGA concentrations. At higher concentrations of PGA more than 40 mM, the q p decreased obviously in a linear way. However, the e.e. of R-MA kept about 95–96.5%, when the PGA concentration was below 60 mM, even at the concentration of PGA 80 mM, the e.e. was still higher than 90%. A modified Monod type equation based on a hypothesis of substrate inhibition could fit the experimental data well. The estimated maximum specific production rate ( q pm) and saturation constant ( K s) were 0.431 mmol gdw −1 h −1 and 5.88 mM, respectively.

Glaciers show direct linkage between erosion rate and chemical weathering fluxes

Field studies suggest a linkage between high physical erosion rates and rates of chemical denudation. Mechanical erosion by temperate glaciers is commonly an order of magnitude higher than in mountainous fluvial catchments, leading to an expectation that chemical weathering fluxes should also be high from glacierized basins. Yet solute fluxes from glaciers are not found to be higher than non-glacierized catchments. Application of a model of silicate weathering from glaciers based on mineral surface area production and mineralogy shows that solute fluxes are consistent with the low temperatures, dilute water chemistry, and high mineral surface area production in these environments. Low temperatures reduce silicate-weathering rates; this effect explains the difference between silica fluxes from glaciers and from non-glacierized basins. As in laboratory flow-through reactors, glacial solute flux should depend on surface area production and mineral weathering rate constants. The surface area production is significant: a typical glacial erosion rate and grain-size distribution produces on the order of 104 km2 of mineral surface area per square kilometer per year. This new surface area is highly reactive because mineral weathering rates decline with surface age. Application of the “reactor” model yields results largely consistent with measured solute fluxes for the example of Bench Glacier, Alaska. The model underpredicts potassium fluxes, probably due to accelerated initial dissolution of biotite strained by abrasion. The success of the model in predicting other silicate weathering fluxes reflects the far-from-equilibrium conditions in glacial runoff, such that mineral weathering rate constants are not limited by saturation state. In a small data set from glacial catchments, both annual silica fluxes and mean concentrations increase with water discharge. This suggests that mineral surface area increases with water discharge from glaciers, an effect plausibly linked to erosion rates. Those glaciers for which both erosion rate and silica flux data are available support the idea that production of new reactive mineral surface area by glacial erosion drives silicate weathering fluxes.

Inhibition effects of ethanol on the kinetics of glucose metabolism by S. cerevisiae: NMR and modelling study

Saccharomyces cerevisiae is an important model to understand the eukaryotic cells control mechanisms. In this Letter, an approach based on in vivo 13C NMR and mathematical modelling was presented to develop a basis for a deeper understanding of eukaryotic responses to environmental stresses. Despite the few metabolites included, the model describes correctly the dynamical behaviour of glucose degradation and ethanol production, providing a qualitative and quantitative description of the response of S. cerevisiae metabolism to stressful concentrations of ethanol. The data and the model highlight that an exogenous stress is able to influence the cellular activity and the ethanol production rate constant.

Microcalorimetric Studies of the Toxic Action of La3+ on Halobacterium Halobium R1 Growth

AbstractA microcalorimetric technique was used to evaluate the influence of La3+ on Halobacterium halobium Rl growth. By means of LKB‐2277 bioactivity monitor, ampoule method at 37 °C, the thermogenic curves of Halobacterium halobium R1 growth were obtained. In order to analyze the results, the maximum power Pm and the growth rate constants k were determined, showing that values of Pm and k are linked to the concentration of La3+. Addition of low concentration of La3+ can cause a decrease of the maximum heat production and growth rate constant. However, high concentration of La3+ may promote growth of Halobacterium halobium R1, but at much higher concentration of La3+, the growth of Halobacterium halobium R1 is inhibited again. For comparison, the shapes of Halobacterium halobium R1 cell were observed by means of transmission electron microscope. According to the thermogenic curves and TEM photos of Halobacterium halobium R1 under different conditions, it is clear that metabolic mechanism of Halobacterium halobium R1 growth is changed with the addition of La3+.

Microcalorimetric investigation of the effect of La3+ on mitochondria isolated from avian chicken liver tissue cells

A microcalorimetric technique was used to evaluate the influence of La3+ on mitochondria isolated from the liver tissue of Avian chicken. By means of LKB-2277 bioactivity monitor, ampoule method at 37°C, we obtained the thermogenic curves of the metabolism of mitochondria. After isolation from the chicken liver tissue, mitochondria still have metabolic activity and can live for a long time depending on the stored nutrients. In order to analyze the results, the maximum power (P m) and the decline rate constants (k d) were obtained. The addition of La3+ results in an increase of the maximum heat production and decline rate constants. Furthermore, values of P m and k d are linked to the concentration of La3+. According to the thermogenic curves under different conditions, it is clear that metabolic mechanism of mitochondria has been changed with the addition of La3+.

KINETICS OF AN ANAEROBIC MOVING BED REACTOR SYSTEM TREATING SYNTHETIC MILK WASTEWATER

ABSTRACT In the present study, anaerobic moving bed reactor called anaerobic rotating biological contactor treating synthetic milk wastewater operated at different organic loading rates and different hydraulic retention times, were evaluated to determine kinetic parameters for the substrate, biomass and biogas based on various models. The maximum substrate loading rate and half velocity constant were evaluated as 5.71 kgCOD/m3ċd and 1178 mg/L respectively by using Lineweaver-Burke plot. Maximum substrate removal efficiency and critical hydraulic retention time were compared with modified Young and McCarty model and the model is best fitted for the study. The complete removal of substrate cannot be expected due to presence of metabolic refractory material produced within the reactor system from influent system. Kinetic constants for maximum specific growth rate and decay coefficient were compared with the modified Monod model. Kornegay and Andrews model were used to evaluate the area capacity constant and half velocity constant. Kinetic constants for maximum specific gas production rate and proportionality constant were evaluated using Stover model. The gas production and quality are dependent on the substrate removal and substrate loading rate. The kinetic relationships derived from lab-scale experiment provided good estimates of the performance of pilot- and full-scale anaerobic rotating biological contactor packed with fibrous nylon pads and treating synthetic milk wastewater in terms of the effluent chemical oxygen demand concentrations and specific biogas production rates.

Biogenic NO emissions from forest and pasture soils: Relating laboratory studies to field measurements

During September and October 1999, dynamic chamber measurements were carried out to determine nitric oxide (NO) fluxes from a primary forest soil and an old pasture in the Brazilian Amazon basin as part of the project “European Studies of Trace Gases and Atmospheric Chemistry as a Contribution to the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia” (LBA‐EUSTACH). In addition, soil samples were collected from these two sites, and laboratory experiments were conducted to determine the NO production and consumption rate constants as functions of soil temperature and soil moisture. These laboratory results were converted into NO fluxes using a simple algorithm, which required additional information on the gas diffusion in soil, the soil bulk density, and the field conditions (soil temperature and soil moisture). Over the entire measurement period, the calculated and measured NO fluxes agreed well both for the forest (6.9 ± 2.9 and 5.0 ± 4.6 ng m−2 s−1, respectively) and for the pasture (0.67 ± 0.09 and 0.65 ± 0.37 ng m−2 s−1, respectively). Forest to pasture conversion decreased NO production and gas diffusion and resulted in smaller NO fluxes from pasture than forest soil.

Reduction in the rate of inositol 1,4,5-trisphosphate synthesis in rat parotid acini by lithium

Stimulation of muscarinic cholinergic receptors on rat parotid acinar cells causes a rapid production of inositol phosphates, with the key metabolic event being the breakdown of phosphatidylinositol 4,5-bisphosphate into inositol 1,4,5-trisphosphate (Ins(1,4,5)P 3) and diacylglycerol. Here a high-performance liquid chromatographic technique was used to measure the effects of intracellular lithium ions on the amount of various inositol phosphates produced. When acini were stimulated maximally with acetylcholine (ACh), the sum of all inositol phosphates produced followed a monoexponential function with a production rate constant for Ins(1,4,5)P 3 of 0.07±0.01 solidus/sec. The presence of 23 mM LiCl intracellularly reduced the production rate constant of Ins(1,4,5)P 3 induced by ACh to 0.03±0.01 solidus/sec, resulting in a decrease in the Ins(1,4,5)P 3 production as well as in the magnitude of the rise in the intracellular free Ca 2+ concentration. The lithium ion (Li +) did not affect the rate of conversion of Ins(1,4,5)P 3 to either inositol 1,4-bisphosphate or inositol 1,3,4,5-tetrakisphosphate. The rate of the inositol phosphate production after the addition of the Ca 2+ ionophore ionomycin was unaffected by intracellular Li + (23 mM), which implies that the action of Li + was at the muscarinic cholinergic receptor, on G-protein or on the interactions between G-proteins and phospholipase C. Thus, in the early events after receptor stimulation with ACh, Li + causes a reduction in the concentration of the cellular messengers Ins(1,4,5)P 3 and Ca 2+.

Comparison of dynamic models to predict the concentration of a photochemical tracer in the upper ocean as a function of depth and time

Three one-dimensional upper-ocean boundary-dynamics models are used to predict the concentration of a short-lived natural photochemical tracer (CO) as a function of time and depth. The models are coupled with parameterizations of the production and destruction rates of the tracer using chemical rate constants from published experimental studies. The model predictions of the upper-ocean [CO] do not agree closely with the measured concentrations obtained during one expedition, probably mostly because of errors in the rate constants used in the chemical model (published values of the in situ rate constants show much variability). An optimization scheme is described to find the values of the production and destruction rate constants that minimize the difference betweenthe modelled and measured upper-ocean [CO], and the uncertainty is assessed by Monte Carlo simulation. Using the optimized estimates of the chemical production and destruction rate constants, the simulated upper-ocean [CO] shows close agreement among the three models. It is still difficult to quantitatively determine which of the models is the best description for observed tracer concentrations because of weaknesses in the existing in situ data sets.

What really is blood compatibility?

The criteria for nonthrombogenicity are classically defined as long clotting times and minimal platelet deposition. The inability to point to unequivocal progress in the development of truly nonthrombogenic materials, highlights the inadequacy if not actually invalidity of these criteria. Our approach is to define nonthrombogenicity in terms of: (1) a thrombin production rate constant, kp < 10-4 cm s-1; (2) low platelet consumption and low degree of platelet activation (e.g., microparticle formation); (3) perhaps some platelet spreading; and (4) low complement and leukocyte activation. Only when the target becomes clear, will it be possible to identify clear strategies for producing the materials we need.

Serotonin transporter production and degradation rates: studies with RTI-76

The objective of this study was to examine the turnover of the serotonin transporter (SERT) by determining its production rate ( r), degradation rate constant ( k) and half-life of recovery ( t 1/2). The turnover of SERT was determined from the rate of recovery of binding after administration of RTI-76, an irreversible inhibitor of ligand binding. In preliminary studies, in vitro incubation of rat cerebral cortex with RTI-76 produced a wash and temperature resistant inhibition of SERT binding densities ( B max). Citalopram protected against the RTI-76-induced inhibition of SERT binding. Following 6 h of in vivo intracerebroventricular injections of 100 nmol of RTI-76, there was a dose- and time-dependent reduction (−60%) of SERT binding in hippocampus and striatum, without a change in the K d. SERT binding densities recovered over several days, reaching control levels by day 14. The recovery curve fit the standard model of protein synthesis and degradation. The turnover parameters of SERT were determined in hippocampus and striatum, regions that receive serotonergic innervation from the dorsal and median midbrain raphe nuclei, respectively. In the hippocampus, the production rate constant was 2.36 fmol mg protein −1 h −1; the degradation rate constant was 0.0077 h −1; and the half-life of the SERT recovery was 3.4 days. The values in the striatum were similar. The decrease and recovery of [ 3 H ]-5-HT uptake correlated highly ( r=0.93) with the recovery of SERT binding.

Allometric Scaling of Rate, Age and Density Parameters in Ecological Models

Over 100 allometric regressions on rate [kg kg -1 = d -1 - d -1 ], age [d] and density [kg km -1 ] parameters often used in ecological models were collected in a literature review. For each parameter, typical coefficients and exponents that covered most of the correlations found were selected. The parameters were checked for consistency by comparing them to each other, e.g. mortality versus age and to independent data, e.g. production and respiration rate constants versus production efficiency. Exponents for consumption, production and respiration rates on the one hand and slopes for maturation, average and maximum age on the other, scale to size with an exponent of the same magnitude but opposite sign. Most values are between ± 0.25 and ± 0.33. No consistent differences between parameters and species were found. Coefficients for production and respiration were largcly consistent with those for ingestion and with independent data on assimilation and production efficiencies. The same was concluded for production versus mortality, for mortality versus age as well as maximum versus average production and consumption. Warm-blooded animals consume, produce and respire at rates about 10 times higher than equally sized coid-blooded species. The reverse was noted for age and possibly density. Population density of individnal species and biota density of geometric size classes are nearly independent of size for regressions that span a wide size range. The coefficients for density vary up to two orders of magnitude, depending on local conditions Most allometric regressions reported apply to aquatic invertebrates or terrestrial birds and mammals of the biophageous food chain. Yet, the rate and age regressions that include other species do not indicate substantial deviations for bacteria, micro-and macrophytes and for terrestrial (saprophagcous) invertebrates. The set of typical values derived may facilitate parameter estimation for generic models. For specific models, the regressions collected in the literature review may provide initial values for parameters.

Nitric oxide emissions from a southern African savanna

NO fluxes from soils of a periodically flooded tropical savanna in southern Africa were investigated and modeled. In the laboratory, NO production rates, NO consumption rate constants, NO mixing ratios, relationships between NO emissions and soil temperature and moisture were determined for nutrient‐poor, nutrient‐rich savanna soils and a floodplain soil. The NO production rate and consumption rate constants of the floodplain soil (1.96 ng N s−1 per kilogram of soil and 2.04×10−5 m3 s−1 per kilogram of soil, respectively) were significantly higher than those of the savanna soils (average of 1.28 ng N s−1 per kilogram of soil and 1.47×10−5 m3 s−1 per kilogram of soil, respectively), but there were no significant difference between the nutrient‐rich and nutrient‐poor soils. NO flux rates increased exponentially with soil temperature. NO flux rates increased with soil moisture reaching a maximum near the field capacity (7.5–10% and 31.2% gravimetric water content for savanna and floodplain soils, respectively), after which the NO flux rate declined. These laboratory data were used in a model to estimate field NO flux rates, which were compared with actual field NO emission measurements. The NO model was modified to incorporate NO “pulsing” after the first rains of the season. Correlation between the modeled and field NO fluxes from the nutrient‐poor savanna, nutrient‐rich savanna, and the floodplain soils showed r2 values of 0.91, 0.82, and 0.74, respectively. The NO model was linked with a soil moisture and temperature model to predict annual NO emission estimates from savannas. Annual NO flux from the nutrient‐poor and nutrient‐rich savannas was estimated to be 0.16×10−3 and 0.14×10−3 kg N m−2 yr−1, respectively, which agree well with estimates from other savanna studies.