Saturation Constant Research Articles

Carbon availability regulates soil respiration response to nitrogen and temperature

The response of soil CO2 fluxes (Rsoil) to interactions between carbon (C) and nitrogen (N) availability or C and temperature conditions is not well understood, but may increasingly affect future C storage under the combined anthropogenic impacts of N deposition and climate change. Here we addressed this uncertainty through a series of laboratory incubation experiments using soils from three contrasting ecosystems to investigate how changes in C, N, and temperature regulate Rsoil through changes to Michaelis–Menten parameters (i.e. Vmax and Km). Results of this study demonstrate that Rsoil response to N enrichment and changes in temperature are dependent on the C availability of soil substrates. N addition influenced Rsoil through both the maximum rate (Vmax) and the half saturation constant (Km). The increase in Km corresponded to a decrease in Rsoil when C was limited. Alternatively, when C was abundant, N enrichment increased Rsoil, which corresponded to an increase in Vmax. Regulation of temperature sensitivity through Vmax and Km was also dependent on C availability. Both Vmax and Km demonstrated positive temperature responses, supporting the hypothesis of a canceling effect at low C concentrations. While temperature sensitivity was influenced by both C quantity and C complexity, our results suggested that C quantity is a stronger predictor. Despite strong differences in climate, vegetation, and management of our soils, C–N and C-temperature interactions were markedly similar between sites, highlighting the importance of C availability in the regulation of Rsoil and justifying the use of Michaelis–Menten kinetics in biogeochemical modeling.

The fluorescent pentameric oligothiophene pFTAA identifies filamentous tau in live neurons cultured from adult P301S tau mice.

Identification of fluorescent dyes that label the filamentous protein aggregates characteristic of neurodegenerative disease, such as β-amyloid and tau in Alzheimer's disease, in a live cell culture system has previously been a major hurdle. Here we show that pentameric formyl thiophene acetic acid (pFTAA) fulfills this function in living neurons cultured from adult P301S tau transgenic mice. Injection of pFTAA into 5-month-old P301S tau mice detected cortical and DRG neurons immunoreactive for AT100, an antibody that identifies solely filamentous tau, or MC1, an antibody that identifies a conformational change in tau that is commensurate with neurofibrillary tangle formation in Alzheimer's disease brains. In fixed cultures of dorsal root ganglion (DRG) neurons, pFTAA binding, which also identified AT100 or MC1+ve neurons, followed a single, saturable binding curve with a half saturation constant of 0.14 μM, the first reported measurement of a binding affinity of a beta-sheet reactive dye to primary neurons harboring filamentous tau. Treatment with formic acid, which solubilizes filamentous tau, extracted pFTAA, and prevented the re-binding of pFTAA and MC1 without perturbing expression of soluble tau, detected using an anti-human tau (HT7) antibody. In live cultures, pFTAA only identified DRG neurons that, after fixation, were AT100/MC1+ve, confirming that these forms of tau pre-exist in live neurons. The utility of pFTAA to discriminate between living neurons containing filamentous tau from other neurons is demonstrated by showing that more pFTAA+ve neurons die than pFTAA-ve neurons over 25 days. Since pFTAA identifies fibrillar tau and other misfolded proteins in living neurons in culture and in animal models of several neurodegenerative diseases, as well as in human brains, it will have considerable application in sorting out disease mechanisms and in identifying disease-modifying drugs that will ultimately help establish the mechanisms of neurodegeneration in human neurodegenerative diseases.

Disease-Induced Chaotic Oscillations and its Possible Control in a Predator–Prey System with Disease in Predator

The effect of parasites and pathogens in prey populations received a lot of attention but disease in predator population has been studied comparatively little in literature. In the present paper we consider a predator–prey model with disease in predator population. We analyze the local stability of model system around the equilibria. We derive the ecological as well as disease basic reproduction numbers and study the community structure of model system by these numbers. We work out the conditions of Hopf bifurcation and persistence of system. Our numerical results reveals that system shows chaotic dynamics for increasing the infection in predator. It is also observe that half saturation constant is responsible for occurrence and control of chaos.

Interactions between hydrogen and Pd-Ag-alloy thin-film structures

The method for measuring the electrical resistance of films is employed to investigate the kinetics of the interaction between hydrogen and thin (25 and 50 nm) films of B1 alloy (more precisely, palladium-silver (Pd83Ag17) alloy) at room temperature. Kinetic curves characterizing hydrogen saturation of the α-phase films of the palladium-based alloy at a pressure of 1 atm, as well as hydrogen release into the medium at a partial pressure close to zero, can be analytically described only if these processes occur under the existence of a single phase. Analysis of the kinetic data indicates that, in the aforementioned mode, hydrogen release from the α phase of the alloy is limited by its diffusion inside the grains of the examined thin films. Since the film thicknesses are small and the coefficient of hydrogen diffusion into the β phase is large, the hydrogenation process is very short and, consequently, makes it impossible to obtain significant saturation constants. The hydrogen concentration interpreted as the equilibrium value determined from saturation curves and corresponding to the solubility of hydrogen in the β phase of the B1 alloy (at a pressure of 1 atm) is much lower than that in coarse-grained or single-crystal samples.

The relationship between light intensity and nutrient uptake kinetics in six freshwater diatoms

In order to find effective measures to control diatom blooms, a better understanding of the physiological characteristics of nutrient uptake in diatoms is needed. A study of P and Si-uptake kinetics for diatom species from two light regimes was conducted at low (LL), moderate (ML) and high light intensities (HL) (2, 25 and 80μmol photons/(m2·sec)), respectively. The results showed that P uptake of diatoms was heavily influenced by historic light regimes. P affinity changed with growth and photosynthetic activity. The lowest half saturation constant for P uptake (Km(P)) was under HL for high-light adapted diatoms while the lowest half-saturation constant for low-light adapted diatoms was observed under LL. The Si half-saturation constant (Km(Si)) increased with increasing light intensities for pennate diatoms but decreased for centric diatoms. Diatom volumes were correlated with the maximum Si uptake rates (Vm(Si)) at HL and Km(Si) at ML and HL for six diatom species. Our results imply that when we assess the development of diatom blooms we should consider light intensity and cell volume in addition to ambient Si or P concentration. The relationship between light intensity and P-uptake suggests that we can find suitable methods to control diatom blooms on the basis of reducing phytoplankton activity of P-uptake and photosynthesis simultaneously.

Biosequestration of CO2 using power plant algae (Rhizoclonium hieroglyphicum JUCHE2) in a Flat Plate Photobio-Bubble-Reactor – Experimental and modeling

Biosequestration of CO2 in a 1.8L Flat Plate Photobio-Bubble-Reactor using power plant algae (Rhizoclonium hieroglyphicum JUCHE2) has been studied. CO2 concentration and light intensity have been varied in the range of 5–25% and 82μmolm−2s−1–398.71μmolm−2s−1, respectively. Dependence of initial specific growth rate of algae has been explained by Haldane type kinetics and by Langmuir–Hinshelwood type kinetics including shape factor with respect to liquid phase CO2 concentration and the intensity of light, respectively. Half saturation constants for CO2 (=Ks) and light (=KE), inhibition constant for CO2 (=KI) and maximum specific growth rate (=μmax) have been determined, respectively as 1.25×10−7Mol/L, 120μmolm−2s−1, 0.00165Mol/L and 0.996d−1. A mathematical model of the Flat Plate Photobio-Bubble-Reactor has been developed incorporating effects of phenomena like gas to liquid mass transfer of CO2, stripping of dissolved CO2 to overhead gas space of the reactor, CO2 uptake by algal biomass. Population dynamics of long term growth of algal biomass have been incorporated by using a Gaussian time function. The model has been validated up to gas phase CO2 concentration of 25% through successful comparison of predicted data with corresponding experimental results.

Experimental Investigation on Sandstone Rock Permeability of Pakistan Gas Fields

Permeability is the ability of formation to produce hydrocarbon which is affected by compaction, pore size, sorting, cementation, layering and clay swelling. The effect of texture on permeability in term of grain size, sorting, sphericity, degree of cementing has been reported in literature. Also, the effect of permeability on capillary pressure, irreducible water saturation, displacement pressure and pore geometry constant has been studied separately. This preliminary study presents the experimental results of eight samples to understand the effect of similar factors of texture on permeability. With the knowledge of the results, it can be said that the effect of grain size, cementation, texture material, sphericity, and porosity can't be observed on permeability except sorting when less than ten samples are considered from different depositional environment. The results also show the impact of permeability on capillary pressure, irreducible water saturation, and displacement pressure and pore geometry index as similar as published in the literature.

Study of moving bed biofilm reactor in diethyl phthalate and diallyl phthalate removal from synthetic wastewater

Phthalic acid esters have received significant attention over the last few years since they are considered as priority pollutants. In this study, effects of different operation conditions including hydraulic retention time, phthalates loading rates and aeration rate on process performance of moving bed biofilm reactor (MBBR) for removing diethyl phthalate (DEP) and diallyl phthalate (DAP) from synthetic wastewater was evaluated. In optimum conditions, 94.96% and 93.85% removal efficiency were achieved for DEP and DAP, respectively. Moreover, MBBR achieved to remove more than 92% of COD for both phthalates. The results showed that DEP had a higher biodegradation rate compared to DAP, according to the selected parameters such as half saturation constant, overall reaction rate and maximum specific growth rate. The Grau second order model found as the best model for predicting MBBR performance due to its high correlation coefficients and more conformity of its kinetic coefficients to the results.

Anaerobic Digestion Treatment of Soft Drink Wastewater

The aim of this study was to treat soft drink industrial wastewater by anaerobic digestion. Digestion lasted for a hydraulic retention time of 30 days. The total quantity of biogas produced was 80ml. The wastewater was characterized after digestion. The result showed that chloride, total dissolved solid, total suspended solid and chemical oxygen demand met the specifications of the world health organization for the safe disposal of wastewater into the water body. The kinetics of anaerobic digestion of the wastewater was described by first order kinetic model. The net specific growth rate of the wastewater was evaluated and observed to reduce with time. The kinetic parameters such as maximum rate of substrate utilization, half velocity or saturation constant, endogenous decay coefficient, biomass or microbial growth yield and maximum specific microorganism growth rate obtained were 0.350day−1, 204.12mg/l, 0.0222day−1, 0.194day−1 and 0.0679day−1 respectively. This revealed that inoculation would be needed for increased volume of biogas production and for an increased digestion rate to be obtained. Based on the endogenous decay coefficient and biomass yield values, a small sludge handling facility would be required in the absence of inoculation during digestion.

Autotrophic perchlorate reduction kinetics of a microbial consortium using elemental sulfur as an electron donor.

The perchlorate reduction kinetic parameters of a microbial consortium using elemental sulfur (S(0)) as an electron donor were investigated in batch experiments. Standard Monod substrate utilization and biomass accumulation models were employed to fit the experimental data for microbial perchlorate reduction. The maximum observed yield coefficient for the microbial consortium was 0.19 mg dry weight (DW) mg(-1) ClO4 (-), suggesting that the microbial consortium had a slow growth rate using S(0) as the electron donor. The maximum specific substrate utilization rate (q max) and half saturation constant (K s) for microbial perchlorate reduction were 0.14 mg ClO4 (-) mg(-1) DW day(-1) and 5.71 mg L(-1), respectively, which indicated that the microbial consortium could effectively utilize perchlorate as an electron acceptor. The variation of q max with pH was described well by using a Gaussian peak equation, and the maximal value of q max was obtained at pH 6.7. The presence of nitrate in perchlorate-contaminated water delayed the onset of sulfur autotrophic perchlorate reduction. The modified Gompertz equation could adequately describe the formation of Cl(-) and SO4(2-) during the process of sulfur autotrophic perchlorate reduction. The SO4(2-) production exceeded the theoretical SO4(2-) production due to S(0) disproportionation. The kinetic parameters for microbial perchlorate reduction are essential to design biological treatment systems, as well as to predict and evaluate their performance.

Optimisation for suspension system of a railway vehicle with a new non-linear creep model developed by uniform design

This paper presents the optimal values of suspension parameters of the railway vehicle system using an integrated procedure for the optimisation. The procedure is composed of uniform design of experiments, hunting stability analysis, kriging interpolation, genetic algorithm and local search optimisation method. The vehicle's nonlinear coupled differential equations of motion with 25 degrees-of-freedom (DOF) are created using the new nonlinear creep model which is developed from the heuristic nonlinear creep model by adding creep moments and the semi-axis lengths in the saturation constant. The performance measure of vehicle systems, vehicle unstable speed, is determined by Lyapunov's indirect method with various wheel conicities. Finally, the optimal solution of suspension parameters of the railway vehicle system under the goal of minimising the combined objective function is found. The results show that this procedure can effectively enhance the robustness of vehicle unstable speed against the noise factor.

Parameter Identification of the Droop Model using Optimal Experiment Design

The Droop model is a classical model used to describe substrate limitation in cultures of microalgae in photobioreactors. In this study, we address the questions of structural identifiability as well as practical identifiability. Optimal experiment design based on the M-criterion is used to determine a small set of experiments that would allow an accurate estimation of the model parameters. Direct and cross-validation results are presented and discussed in the framework of a simulation study. As a result, all parameters are found to be structurally identifiable and two continuous experiments are proposed that target either the estimation of the maximum substrate uptake rate and maximum growth rate, or the half saturation constant of the uptake rate, respectively.

PFTAA: a high affinity oligothiophene probe that detects filamentous tau in vivo and in cultured neurons.

Tauopathies describe a group of neurodegenerative diseases in which the protein tau, encoded by the gene MAPT, is aberrantly misfolded, leading to tau aggregation, neural dysfunction, and cell death (Spillantini and Goedert, 2013). In Alzheimer's disease (AD), tau forms the characteristic intracellular neurofibrillary tangles (NFTs), which are thought to be the major cause of neurodegeneration (Bloom, 2014). In other tauopathies, including frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17T), corticobasal degeneration and progressive supranuclear palsy, there are specific forms of tau aggregates and filaments without any amyloid pathology, demonstrating tau's potent disease-causing potential (Spillantini and Goedert, 2013). Tau is a microtubule (MT) binding protein, which becomes abnormally hyperphosphorylated on several residues prior/during the process of aggregation, thereby causing loss of its MT binding activity (Mandelkow and Mandelkow, 2012). The importance of tau as a single cause of disease is reinforced by the identification of numerous (> 55) mutations in autosomal-dominant forms of familial tauopathies, many of which occur in the MT binding domain. Indeed, more and more diseases are being uncovered in which aberrant phosphorylation and folding of tau is implicated, not least in Huntington's disease (HD), while MAPT is a genetic risk factor for Parkinson's disease (PD), so it is of major interest to understand how it leads to cell dysfunction and death.

Biodegradation kinetics of tetrahydrofuran, benzene, toluene, and ethylbenzene as multi-substrate by Pseudomonas oleovorans DT4.

The biodegradation kinetics of tetrahydrofuran, benzene (B), toluene (T), and ethylbenzene (E) were systematically investigated individually and as mixtures by a series of aerobic batch degradation experiments initiated by Pseudomonas oleovorans DT4. The Andrews model parameters, e.g., maximum specific growth rates (μmax), half saturation, and substrate inhibition constant, were obtained from single-substrate experiments. The interaction parameters in the sum kinetics model (SKIP) were obtained from the dual substrates. The μmax value of 1.01 for tetrahydrofuran indicated that cell growth using tetrahydrofuran as carbon source was faster than the growth on B (μmax, B = 0.39) or T (μmax, T = 0.39). The interactions in the dual-substrate experiments, including genhancement, inhibition, and co-metabolism, in the mixtures of tetrahydrofuran with B or T or E were identified. The degradation of the four compounds existing simultaneously could be predicted by the combination of SKIP and co-metabolism models. This study is the first to quantify the interactions between tetrahydrofuran and BTE.

Evaluation of Several Mathematical Models for Fitting the Growth and Kinetics of the Catechol-degrading Candida parapsilopsis: Part 2

Kinetic equations, which describe the activity of an enzyme or a microorganism on a particular substrate, are crucial in understanding many phenomena in biotechnological processes. They allow the mathematical prediction of growth parameters important for identifying key parameters for controlling growth. We remodelled the published work of Rigo et al. (2010) using several more growth kinetic models such as Monod, Haldane, Teissier, Andrews and Noack, Hinshelwood, Moser, Aiba, Webb (Edward), Yano and Koga, Han and Levenspiel and Luong and evaluated the accuracy of the fitted model using statistical analysis such as Root Mean Square (RMSE), adjusted Coefficient of Determination (R2), corrected Akaike Information Criterion (AICc), Bias Factor and Accuracy Factor The accuracy and statistical analysis of the eleven kinetic models used shows that only the Haldane, Teissier, Moser, Aiba, Webb (Edward), Yano and Koga, and Luong could fit the data with the best model was Haldane with low values for RMSE and AICc, highest adjusted R2 values, and with Bias Factor and Accuracy Factor nearest to unity (1.0). The calculated value for the Haldane constants maximal degradation rate, half saturation constant and half inhibition constant symbolized by μmax, Ks and Ki, were 0.462 hr-1, 112.21 mg/L and 211.34 mg/L, respectively. The true umax value occurs where the gradient for the slope is zero and in this case the value was approximately 0.188 h-1 at 155 mg/L catechol. The results indicate that the exhaustive use of mathematical models on available published results could gleam new optimal models that can provide new knowledge on the way toxicsubstance inhibit growth rate in microbes.

Kinetic coefficients for the domestic wastewater treatment using hybrid activated sludge process

In this study, the performance of a novel configuration of the hybrid growth bioreactor in pilot-plant scale (containing of anoxic, aerobic and sedimentation sections) was investigated for Isfahan municipal wastewater treatment plants. The bioreactor performance was evaluated after primary sedimentation tanks under the inlet COD concentration of 0.27±0.02 g/L, at different suspended biomass concentrations of about 3, 4, and 5 as g/L and different total hydraulic retention times 4, 8, and 12 h. An industrial moving bed packing with protected specific surface area of 350 m2/m3 was used in the bioreactor with a 30% of filling ratio. The modified Stover–Kincannon and Grau models are applied to predict the bio kinetic coefficients of COD removal. According to the results obtained, the substrate removal rate constant (ks) for Grau model was in the range of 8.23–10.96 (1/d), and the saturation constant (KB) value and the maximum total substrate utilization rate (Umax) for modified Stover–Kincannon were in the range of 57.4–87.7 (g/L d) and 62.6–91.4 (g/L d), respectively. Also, the results showed that the bioreactor follows the models with 98–99% correlation coefficients.

Kinetic Analysis for COD Removal in Actual Coking Wastewater through an Micro-Aerobic EGSB Reactor

Treatment of actual coking wastewater considered to be difficult by traditional systems. The present study is related to treatment of actual coking wastewater through microaerobic EGSB reactor. The study showed the EGSB reactor could attain about 75% high COD removal. IncreasingVupcould strength COD removal. Moreover, high sludge concentration and profound communal synergism existing within the dense granules were very important. As a result of the kinetic analysis of the EGSB reactor treating actual coking wastewater for COD removal using a modified Stover–Kincannon model, the maximum substrate utilization rate,vmax, half saturation constant,KS, inhibitor constant, KI, actual pollutant removal rate, , and the actual inhibition degree,KS/KIwere determined as 2.65×10-3h-1, 39.57mg.L-1, 415.82mg.L-1, 6.7×10-5h-1.mg-1.L and 0.1(before increasingVup), 7.34×10-3h-1, 19.53mg.L-1, 197.76mg.L-1, 3.7×10-4h-1.mg-1.L and 0.1(after increasingVup), and 9.35×10-3h-1, 6.38mg.L-1, 162.81mg.L-1, 1.47×10-3h-1.mg-1.L and 0.04 (after increasingVupand X), respectively. The inhibition of toxic contaminants in the actual coking wastewater would cause the decreasing of pollutant removal rate, however, enhancing and X (simultaneously optimizing sludge aggregate structure) could strengthen the performance effect.

Nitric oxide preferentially inhibits nitrite oxidizing communities with high affinity for nitrite

The prerequisite to the development success of the novel mainstream processes partial nitritation/anammox is the out-selection of nitrite oxidizing bacteria (NOB). A recent study suggested that this could be achieved through NO production by ammonium oxidizing bacteria under cyclic oxic–anoxic conditions. Indeed, it is known that among NOB, Nitrobacter species are reversibly inhibited by NO. However, the effect of NO on the activity of the NOB genus Nitrospira is not studied so far. Such an understanding is needed, since Nitrospira related NOB are mostly prevailing in sewage treatment plants. This study quantified the effect of NO on the nitratation activity of sludge types with different Nitrobacter/Nitrospira ratios. In an oxic bubbling column, a dosage of 4.4mg NOL−1d−1 (∼2μgNO–NL−1 in liquid phase) inhibited the Nitrobacter dominated sludge with 24%. For the Nitrospira dominated sludge types, the inhibition was strongly correlated with the nitrite half saturation constant (Ks) ranging from 0% to 30–50% and 60–80% inhibition of the nitrite oxidation for Ks of 0.72, 0.36 and 0.06mg NO2−–NL−1, respectively. This study showed that nitrifying communities with high affinity for nitrite and low specific nitrite oxidation rates (K-strategists) can be strongly inhibited by NO. The degree of inhibition could be confirmed in a set-up with NO dosage through an artificial alginate-based biofilm, ensuring a more direct contact between NO and the microorganisms.

A PREDATOR–PREY INTERACTION MODEL WITH SELF- AND CROSS-DIFFUSION IN AQUATIC SYSTEMS

In this paper, the complex dynamics of a spatial aquatic system in the presence of self- and cross-diffusion are investigated. Criteria for local stability, instability and global stability are obtained. The effect of critical wavelength which can drive a system to instability is investigated. We noticed that cross-diffusion coefficient can be quite significant, even for small values of off-diagonal terms in the diffusion matrix. With the help of numerical simulation, we observed the Turing patterns (spots, strips, spot-strips mixture), regular spiral patterns and irregular patchy structures. The beauty and complexity of the Turing patterns are attributed to a large variety of symmetry properties realized by different values of predator's immunity, rate of fish predation and half saturation constant of predator population.

Biodegradation of Isopropanol by a Solvent-Tolerant Paracoccus denitrificans Strain

The biodegradation of high concentration isopropanol (2-propanol, IPA) at 16 g/L was investigated by a solvent-tolerant strain of bacteria identified as Paracoccus denitrificans for the first time by 16S rDNA gene sequencing. The strain P. denitrificans GH3 was able to utilize the high concentration of IPA as the sole carbon source within a minimal salts medium with a cell density of 1.5 × 108 cells/mL. The optimal conditions were found as follows: initial pH 7.0, incubation temperature 30°C, with IPA concentration 8 g/L. Under the optimal conditions, strain GH3 utilized 90.3% of IPA in 7 days. Acetone, the major intermediate of aerobic IPA biodegradation, was also monitored as an indicator of microbial IPA utilization. Both IPA and acetone were completely removed from the medium following 216 hr and 240 hr, respectively. The growth of strain GH3 on IPA as a sole carbon and energy source was well described by the Andrews model with a maximum growth rate (μ max ) = 0.0277/hr, a saturation constant (K S ) = 0.7333 g/L, and an inhibition concentration (Ki) = 8.9887 g/L. Paracoccus denitrificans GH3 is considered to be well used in degrading IPA in wastewater.