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  • 1
    Electronic Resource
    Electronic Resource
    Sensitivity of PSA process performance to input variables (1995)
    Springer
    Adsorption 1 (1995), S. 133-151 
    Details
    ISSN: 1572-8757
    Keywords: PSA process ; sensitivity ; equilibria ; kinetics ; heats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Mathematical models for pressure swing adsorption (PSA) processes essentially require the simultaneous solutions of mass, heat and momentum balance equations for each step of the process using appropriate boundary conditions for the steps. The key model input variables needed for estimating the separation performance of the process are the multicomponent adsorption equilibria, kinetics and heats of adsorption for the system of interest. A very detailed model of an adiabatic Skarstrom PSA cycle for production of high purity methane from a ethylene-methane bulk mixture is developed to study the sensitivity of the process performance to the input variables. The adsorption equilibria are described by the heterogeneous Toth model which accounts for variations of isosteric heats of adsorption of the components with adsorbate loading. A linear driving force model is used to describe the kinetics. The study shows that small errors in the heats of adsorption of the components can severely alter the overall performance of the process (methane recovery and productivity). The adsorptive mass transfer coefficients of the components also must be known fairly accurately in order to obtain precise separation performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705001
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  • 2
    Electronic Resource
    Electronic Resource
    Frequency response analysis of a closed diffusion cell with two resonators (1996)
    Springer
    Adsorption 2 (1996), S. 265-277 
    Details
    ISSN: 1572-8757
    Keywords: frequency response ; diffusion cell ; kinetics ; diffusion ; heat effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This paper deals with frequency response (FR) analysis of a closed diffusion cell system with two resonators, that is both the LHS and RHS volumes are modulated. The analysis is made for a homogeneous particle described by a single effective diffusivity as well as a biporous pellet described by macropore and micropore diffusions. It is shown that if the perturbation of the volume of the reservoir #2 is lagged behind that of the reservoir #1 by 3π/2, the pressure response in reservoir #1 is significantly enhanced with larger amplitude as well as phase angle. When the perturbations of the two reservoirs are out of phase, the heat effect is reduced and can become insignificant when the two perturbations are completely out of phase (ψ = π). Under such a condition, the pressure difference between the two reservoirs could be doubled. In the case of biporous pellets, it is shown that the FR behaviours obtained for micropore diffusion control and macropore diffusion control are well distinguished. In the former case, the FR system reduces to a traditional batch adsorber one while in the latter case, the FR behaviour is the same as for a two resonator system with homogeneous particles. This difference can be used for the discrimination of micropore and macropore diffusion processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879541
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  • 3
    Electronic Resource
    Electronic Resource
    Equilibria and kinetics characterisation of two different structured nutshell-derived activated carbons (1997)
    Springer
    Adsorption 3 (1997), S. 267-275 
    Details
    ISSN: 1572-8757
    Keywords: characterisation ; equilibria ; kinetics ; micropore size distribution ; n-butane ; nutshell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Adsorption equilibria and dynamics ofn-butane on two activated carbon samples prepared from the physical activation of nutshell are studied in this paper. The micropore size distribution (MPSD) is considered as the main source of solid heterogeneity. Lennard-Jones' potential theory and Dubinin's theory (TVFM) are used in the equilibria data to derive the MPSD, which is well fitted by a Gamma distribution function. The adsorption energy distribution derived from the MPSD is very asymmetric for both the samples studied, and this energy distribution used in the HMSD/HMSMD kinetics models for the study of adsorption dynamics ofn-butane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01653629
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  • 4
    Electronic Resource
    Electronic Resource
    Prediction of paper permanence by accelerated aging II. Comparison of the predictions with natural aging results (1996)
    Springer
    Cellulose 3 (1996), S. 269-279 
    Details
    ISSN: 1572-882X
    Keywords: accelerated tests ; aging tests ; cellulose degradation ; durability ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Accelerated aging tests are credible and useful to predict paper permanence only if such tests can be shown to correlate with natural aging. In the first part of this study, a kinetic model was developed based on the accelerated aging results. In this report, we have shown that this kinetic model can indeed predict the natural aging results of lignin-free sheets with a statistical confidence. This is the first quantitative comparison of accelerated aging with natural aging.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02228806
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  • 5
    Electronic Resource
    Electronic Resource
    On the kinetics of degradation of cellulose (1997)
    Springer
    Cellulose 4 (1997), S. 1-5 
    Details
    ISSN: 1572-882X
    Keywords: paper ; degradation ; ageing ; kinetics ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018408515574
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  • 6
    Electronic Resource
    Electronic Resource
    Prediction of paper permanence by accelerated aging I. Kinetic analysis of the aging process (1996)
    Springer
    Cellulose 3 (1996), S. 243-267 
    Details
    ISSN: 1572-882X
    Keywords: aging tests ; cellulose degradation ; durability ; kinetics ; paper properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The validity of accelerated aging tests to predict and rank papers on their permanence has been under question, preventing the development of performance-based standards for permanent paper. We conducted a general kinetic analysis to investigate the aging process of paper. A general kinetic model is proposed to describe the depolymerization of cellulose. Experimentally it was shown that in the case of aging, cellulose degradation follows classic first-order kinetics as a special case of our general kinetic model. The Arrhenius equation was critically re-examined for the case of a multiple reaction system. It was shown analytically that the Arrhenius equation is still applicable when certain conditions are met. This was convincingly supported by experimental results. We also analysed the dependence of the degradation rate on the moisture content and hydrogen ion concentration. By conducting systematic experiments on these two factors, a general and quantitative relationship was established to explain the contribution of each factor and their interactions. Finally, based on this kinetic analysis, the effects of storage conditions on the life expectancy of paper were estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02228805
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  • 7
    Electronic Resource
    Electronic Resource
    Sorption Equilibria and Kinetics of Hydrocarbons onto Activated Carbon Samples Having Different Micropore Size Distributions (1999)
    Springer
    Adsorption 5 (1999), S. 25-37 
    Details
    ISSN: 1572-8757
    Keywords: micropore size distribution ; activated carbon ; adsorption ; desorption ; equilibrium ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This paper deals with the prediction of adsorption equilibrium and kinetics of hydrocarbons onto activated carbon samples having different micropore size distribution (MPSD). The microporous structure of activated carbon is characterised by the distribution of slit-shaped micropores, which is assumed to be the sole source of surface heterogeneity. The interaction between adsorbate molecule and pore walls is described by the Lennard-Jones potential theory. Different adsorbates have access to different pore size range of activated carbon due to the size exclusion, a phenomenon could have a significant influence on both multicomponent equilibria and kinetics. Activated carbons with three different MPSDs are studied with ethane and propane as the two model adsorbates. The Heterogeneous Macropore Surface Diffusion model (HMSD) is employed to simulate adsorption kinetics. The simulation results show that the MPSD is an important factor affecting both the multicomponent equilibria and kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026481704926
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  • 8
    Electronic Resource
    Electronic Resource
    Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)
    Springer
    Adsorption 5 (1999), S. 145-158 
    Details
    ISSN: 1572-8757
    Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008917308002
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  • 9
    Electronic Resource
    Electronic Resource
    Hybridomas in a bioreactor cascade: modeling and determination of growth and death kinetics (1996)
    Springer
    Cytotechnology 21 (1996), S. 263-277 
    Details
    ISSN: 1573-0778
    Keywords: hybridomas ; serum-free medium ; monoclonal antibodies ; reactor series ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hybridomas were cultured under steady-state conditions in a series of two continuous stirred-tank reactors (CSTRs), using a serum-free medium. The substrate not completely converted in the first CSTR, was transported with the cells to the second one and very low growth rates, high death rates, and lysis of viable cells were observed in this second CSTR. These conditions are hardly accessible in a single vessel, because such experiments would be extremely time-consuming and unstable due to a low viability. In contrast to what is often observed in literature, kinetic parameters could thus be derived without the neccessity for extrapolation to lower growth rates. Good agreement with literature averages for other hybridomas was found. Furthermore, showing that the reactor series is a valuable research tool for kinetic studies under extreme conditions, the possibility to observe cell death under stable and defined steady-state conditions offers interesting opportunities to investigate apoptosis and necrosis. Additionally, a model was developed that describes hybridoma growth and monoclonal antibody production in the bioreactor cascade on the basis of glutamine metabolism. Good agreement between the model and the experiments was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365349
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  • 10
    Electronic Resource
    Electronic Resource
    Kinetics and equilibria of condensation reactions between monosaccharide pairs catalyzed by Aspergillus niger glucoamylase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 9-22 
    Details
    ISSN: 0006-3592
    Keywords: condensation reactions ; disaccharides ; equilibria ; glucoamylase ; kinetics ; monosaccharides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Arabinose, fructose, galactose, myo-inositol, lyxose, mannose, ribose, and xylose were incubated individually and with glucose in the presence of Aspergillus niger glucoamylase at pH 4.5 and 45°C. Glucoamylase condenses galactose, glucose, and mannose individually into disaccharides. It also produces mixed disaccharides when each of the eight carbohydrates is incubated with glucose. Many products were identified by gas chromatography of the derivatized reaction mixtures followed by mass spectroscopy of the individual chromatographic peaks. Galacto-, gluco-, or mannopyranosyl rings appear to be present at the nonreducing ends of all the disaccharides produced. Molecules linked through primary hydroxyl groups have the highest equilibrium constants of all products formed, since these bonds are thermodynamically favored. However, glucoamylase is capable of forming bonds with many available hydroxyl groups, as previously demonstrated when it was incubated with glucose alone. Formation rates of different bonds linking different residues vary widely. These results demonstrate that glucoamylase has a wide selectivity toward residues it will condense into disaccharides and toward bonds it will form between them. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 9-22, 1997.
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  • 11
    Electronic Resource
    Electronic Resource
    Effect of hypoxia duration on the oxygen-dependent production of a recombinant protein, β-galactosidase, by an animal cell line, F6D2, with a hypoxia-inducible enhancer (1997)
    Springer
    Cytotechnology 25 (1997), S. 71-77 
    Details
    ISSN: 1573-0778
    Keywords: hypoxia ; recombinant protein ; animal cells ; erythropoietin ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Expression of specific genes is a strategy of animal cells for adaptation to oxygen deficiency and the mechanism underlying the hypoxic activation of gene expression may be useful for efficient production of recombinant proteins by animal cells, because oxygen is a limiting factor in animal cell cultures. We prepared an animal cell line harboring the plasmid in which expression of a reporter gene, β-galactosidase, is controlled by an enhancer responsible for the hypoxic activation of gene transcription. The purpose of this paper is to understand this hypoxic production of recombinant proteins quantitatively by a mathematical model originally developed based on the following hypotheses; 1 lacZ (the reporter gene) is transcribed after HIF-1 protein complex is bound to the hypoxic enhancer, 2. β-galactosidase synthesis rate is limited at the transcription of lacZ, 3. HIF-1 is an inactive form under a normal oxygen concentration, 4. Oxygen works as a repressor in the synthesis of HIF-1 protein, 5. Both β-galactosidase and HIF-1 are decomposed according to the first order reaction. The effects of hypoxic duration as well as oxygen concentration on the β-galactosidase production were successfully predicated by the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007911816292
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  • 12
    Electronic Resource
    Electronic Resource
    Chlorine decay and bacterial inactivation kinetics in drinking water in the tropics (1996)
    Springer
    World journal of microbiology and biotechnology 12 (1996), S. 549-556 
    Details
    ISSN: 1573-0972
    Keywords: Bacteria inactivation ; chlorine decay ; combined chlorine ; drinking water ; free chlorine ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The decay of free chlorine (Cl2) and combined chlorine (mostly monochloramine: NH2Cl) and the inactivation of bacteria was examined in Dar es Salaam, Tanzania. Batch experiments, pilot-scale pipe experiments and full-scale pipe experiments were carried out to establish the kinetics for both decay and inactivation, and to compare the two disinfectants for use under tropical conditions. The decay of both disinfectants closely followed first order kinetics, with respect to the concentration of both disinfectant and disinfectant-consuming substances. Bacterial densities exhibited a kinetic pattern consisting of first order inactivation with respect to the density of the bacteria and the concentration of the disinfectant, and first order growth with respect to the bacterial density. The disinfection kinetic model takes the decaying concentration of the disinfectant into account. The decay rate constant for free chlorine was 114 lg-1h-1, while the decay rate constant for combined chlorine was 1.84 lg-1h-1 (1.6% of the decay rate for free chlorine). The average concentration of disinfectant consuming substances in the water phase was 2.6 mg Cl2/l for free chlorine and 5.6 mg NH2Cl/l for combined chlorine. The decay rate constant and the concentration of disinfectant consuming substances when water was pumped through pipes, depended on whether or not chlorination was continuous. Combined chlorine especially could clean the pipes of disinfectant consuming substances. The inactivation rate constant λ, was estimated at 3.06×104 lg-1h-1. Based on the inactivation rate constant, and a growth rate constant determined in a previous study, the critical concentration of free chlorine was found to be 0.08 mg Cl2/l. The critical concentration is a value below which growth rates dominate over inactivation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00419471
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  • 13
    Electronic Resource
    Electronic Resource
    A structured metabolic model for anaerobic and aerobic stoichiometry and kinetics of the biological phosphorus removal process (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 277-287 
    Details
    ISSN: 0006-3592
    Keywords: phosphorus removal ; biological ; kinetics ; metabolic model ; polyphosphate ; PHB ; glycogen ; batch reactor, sequenced ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A structured metabolic model is developed that describes the stoichiometry and kinetics of the biological P removal process. In this approach all relevant metabolic reactions underlying the metabolism, considering also components like adenosine triphosphate (ATP) and nic-otinamide-adenine dinucleotide (NADH2) are describedbased on biochemical pathways. As a consequence of the relations between the stoichiometry of the metabolic reactions and the reaction rates of components, the required number of kinetic relations to describe the process is reduced. The model describes the dynamics of the storage compounds which are considered separately from the active biomass. The model was validated in experiments at a constant sludge retention time of 8 days, over the anaerobic and aerobic phases in which the external oncentrations as well as the internal fractions of the relevant components involved in the P-removal process were monitored. These measurements include dissolved acetate, phosphate, and ammonium; oxygen consumption; poly-β-hydroxybutyrate (PHB); glycogen; and active biomass. The model satisfactorily describes the dynamic behavior of all components during the anaerobicand aerobic phases.© 1995 John Wiley & Sons, Inc
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470302
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  • 14
    Electronic Resource
    Electronic Resource
    Kinetics of phase separation for polyethylene glycol-phosphate two-phase systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 246-256 
    Details
    ISSN: 0006-3592
    Keywords: polyethylene glycol ; phosphate ; phase separation ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Phase separation times for polyethylene glycol (PEG)-4000-phosphate aqueous two-phase systems were studied, for small scale (5-g) and large scale (1300-g) systems, as a -function of the stability ratio. Profiles of dispersion height for both large and small scale systems were represented as a fraction of the initial height and were found to be independent of the geometrical dimensions of the separator. Furthermore, by plotting time as a fraction of the initial height the total time of separation can be calculated for a given height of system at a particular stability ratio. This generalization is important for the design of large scale aqueous two-phase separators. Phase separation times were also found to be dependent on which of the phases is continuous. A characteristic change in phase separation time was also observed at the phase inversion point (i.e., where the dispersed phase changes to a continuous phase and vice versa) and this point tends toward higher volume ratios as the tie-line length (TLL) is increased. Furthermore, the phase inversion point at each TLL corresponds to a fixed phosphate concentration. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480311
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  • 15
    Electronic Resource
    Electronic Resource
    Kinetics of nitrate inhibition of carbon tetrachloride transformation by a denitrifying consortia (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 279-284 
    Details
    ISSN: 0006-3592
    Keywords: carbon tetrachloride ; nitrate inhibition ; biodegradation ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of nitrate inhibition of carbon tetrachloride (CT) transformation were examined using a denitrifying consortium. Comparison of data from fed-batch experiments to the model reported by Hooker et al. indicate that the inhibition constant ranges between 3.2 and 21 mg/L, with an average of 8.8 mg/L. This range is much lower than the previously reported value of 169 mg/L. Simulations using the corrected parameter accurately reflect this new data and the data reported by Hooker et al. In contrast, the earlier reported coefficient value does not reflect the data reported in this work. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450314
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  • 16
    Electronic Resource
    Electronic Resource
    Catalytic behavior of Pseudomonas cepacia lipase in w/o microemulsions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 33-41 
    Details
    ISSN: 0006-3592
    Keywords: lipase ; reverse micelles ; surfactants ; esterification ; glycerides ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The activity of purified Pseudomonas cepacia lipase has been investigated in esterification reactions of various aliphatic alcohols with natural fatty acids. The reactions were carried out in microemulsions formed in isooctane by bis-(2-ethylhexyl)sulfosuccinate sodium salt (AOT). Kinetic studies showed that the reaction follows a ping-pong bi-bi mechanism with inhibition by both substrates. The apparent kinetic parameters of the reaction were found to be Km octanol = 310 mM, Km lauric acid = 78 mM, and Vmax = 250 μmol min-1 mg-1. The same system was used for the synthesis of mono- and diglycerides from glycerol and lauric acid, which was successful at very low wo values. The catalytic behavior of P. cepacia lipase was also studied in esterification reactions performed in a nonionic microemulsion system formulated by tetraethyleneglycoldodecylether (C12E4). The optimum activity was found at about wo = 8. The apparent values of Vmax app and Km app for octanol were calculated and found to be 100 μmol min-1 mg-1 and 76 mM, respectively. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450106
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  • 17
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    The Monod equation and mass transfer (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 91-94 
    Details
    ISSN: 0006-3592
    Keywords: mass transfer ; Monod equation ; growth rate ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An alternative interpretation of the growth rate-substrate concentration dependence is presented. This is based on the assumption that the main factors affecting growth rate are transfer of substrate from the medium and the maximum growth velocity, which is that observed when no substrate limitations occur. This approach allows the approximate prediction of one of the two kinetic constants required, and may be of great use, especially for continuous cultures. It is the first attempt to provide a phenomenological explanation for the large variations observed in the values of the Monod constant, Ks, reported in the literature. © 1995 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450113
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  • 18
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    Effect of yeast extract on growth kinetics during aerobic biodegradation of chlorobenzoic acids (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 227-233 
    Details
    ISSN: 0006-3592
    Keywords: chiorobenzoic acids ; yeast extract ; kinetics ; growth kinetics ; dechlorination ; biodegradation ; Pseudomonas ; Alcaligenes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Monod or Andrews kinetic parameters describing the growth of Pseudomonas sp. CPE2 strain on 2,5-dich!orobenzoic acid and 2-chlorobenzoic acid, and Al-caligenes sp. CPE3 strain on 3,4-dichlorobenzoic acid, 4-chlorobenzoic acid, and 3-chlorobenzoic acid were determined from batch and continuous growth experiments conducted in the presence or absence of yeast extract (50 mg/L). Strain CPE2 displayed inhibitory growth kinetics in the absence of yeast extract and a noninhibitory kinetics in the presence of yeast extract. Similar results were obtained for CPE3. The presence of yeast extract also resulted in a significant increase in the affinity of the strains for the chlorobenzoic acids they degraded. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260470214
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  • 19
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    The Use of RP-HPLC for measuring activation and cleavage of rFVIIa during purification (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 501-505 
    Details
    ISSN: 0006-3592
    Keywords: RP-HPLC ; rFVIIa ; activation ; cleavage ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A reverse phase HPLC (RP-HPLC) method for analysis of recombinant factor VIIa (rFVIIa) has been developed. The method discriminates between different forms of recombinant FVII (rFVII). To obtain separation of these closely related molecules the method has been optimized with respect to gradient profile and temperature. The method has been used for optimization of purification processes and for kinetic studies. EVidence for autolytic cleavage was obtained. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260480512
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  • 20
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    Determination of carbon dioxide evolution rate using on-line gas analysis during dynamic biodegradation experiments (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 243-252 
    Details
    ISSN: 0006-3592
    Keywords: carbon dioxide evolution rate ; mass transfer ; modeling ; biodegradation ; pH ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Respirometry is a precious tool for determining the activity of microbial populations. The measurement of oxygen uptake rate is commonly used but cannot be applied in anoxic or anaerobic conditions or for insoluble substrate. Carbon dioxide production can be measured accurately by gas balance techniques, especially with an on-line infrared analyzer. Unfortunately, in dynamic systems, and hence in the case of short-term batch experiments, chemical and physical transfer limitations for carbon dioxide can be sufficient to make the observed carbon dioxide evolution rate (OCER) deduced from direct gas analysis very different from the biological carbon dioxide evolution rate (CER).To take these transfer phenomena into account and calculate the real CER, a mathematical model based on mass balance equations is proposed. In this work, the chemical equilibrium involving carbon dioxide and the measured pH evolution of the liquid medium are considered. The mass transfer from the liquid to the gas phase is described, and the response time of the analysis system is evaluated.Global mass transfer coefficients (KLa) for carbon dioxide and oxygen are determined and compared to one another, improving the choice of hydrodynamic hypotheses. The equations presented are found to give good predictions of the disturbance of gaseous responses during pH changes.Finally, the mathematical model developed associated with a laboratory-scale reactor, is used successfully to determine the CER in nonstationary conditions, during batch experiments performed with microorganisms coming from an activated sludge system. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 243-252, 1997.
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    Identification of linearity in the biofilm process and its operational utility (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 253-258 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; deep biofilm reactor (DBFR) ; kinetics ; linearity ; operational control ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various reported field studies on the performance of biofilm reactors suggest that the linear control of the system is effective for maintaining the consistent treatment efficiency under changing environmental conditions. However, no theoretical basis is available in the literature to substantiate such a claim. In this article, inherent linearity of the biofilm process has been identified along with the conditions under which this linearity exists. Exploiting the linear state of the system, operational criteria for regulating the performance of the biofilm reactors are obtained. The utility and applicability of the developed criteria are numerically demonstrated. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 253-258, 1997.
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    Kinetics and modeling of GM-CSF production by recombinant yeast in a three-phase fluidized bed bioreactor (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 470-477 
    Details
    ISSN: 0006-3592
    Keywords: fluidized bed bioreactor ; recombinant ; yeast ; kinetics ; modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous production of a recombinant murine granulocyte-macrophage colony-stimulating factor (GM-CSF) by Saccharomyces cerevisiae strain XV2181 (a/a, Trp 1) containing plasmid pαADH2 and immobilized on porous glass beads in a fluidized bed bioreactor was studied. Kinetic models for plasmid stability, cell growth, and protein production in the three-phase fluidized bed bioreactor were developed and used to study the effects of solid loading or cell immobilization on plasmid stability and recombinant protein production. With increasing cell immobilization or solid loading in the bioreactor, plasmid stability and protein production improved significantly. The improvements could be attributed to the decreased θ value, which is the plasmid loss probability during cell division and is an indication of segregational instability of the recombinant cell, and the increased α value, which is the ratio of the specific growth rate of a plasmid-carrying cell to that of a plasmid-free cell and is indicative of competitive stability of the recombinant cell culture. θ decreased from 0.552 to 0.042 and α increased from 0.351 to 0.991 when solid loading in the bioreactor was increased from 5% (v/v) to 33%. The model simulation also showed that the specific growth rate of cells in the bioreactor was lower at higher solid loading. This indicated that there was significant mass transfer limitation, particularly for oxygen transfer, when the total cell density in the bioreactor was high at high solid loading. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 470-477, 1997.
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    Kinetics of U(VI) reduction by a dissimilatory Fe(III)-reducing bacterium under non-growth conditions (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 490-496 
    Details
    ISSN: 0006-3592
    Keywords: uranium ; kinetics ; precipitation ; shewanella ; metal reduction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dissimilatory metal-reducing microorganisms may be useful in processes designed for selective removal of uranium from aqueous streams. These bacteria can use U(VI) as an electron acceptor and thereby reduce soluble U(VI) to insoluble U(IV). While significant research has been devoted to demonstrating and describing the mechanism of dissimilatory metal reduction, the reaction kinetics necessary to apply this for remediation processes have not been adequately defined. In this study, pure culture Shewanella alga strain BrY reduced U(VI) under non-growth conditions in the presence of excess lactate as the electron donor. Initial U(VI) concentrations ranged from 13 to 1680 μM. A maximum specific U(VI) reduction rate of 2.37 μmole-U(VI)/(mg-biomass h) and Monod half-saturation coefficient of 132 μM-U(VI) were calculated from measured U(VI) reduction rates. U(VI) reduction activity was sustained at 60% of this rate for at least 80 h. The initial presence of oxygen at a concentration equal to atmospheric saturation at 22°C delays but does not prevent U(VI) reduction. The rate of U(VI) reduction by BrY is comparable or better than rates reported for other metal reducing species. BrY reduces U(VI) at a rate that is 30% of its Fe(III) reduction rate. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 490-496, 1997.
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    A rapid method for determining kinetic parameters of enzymes exhibiting nonlinear thermal inactivation bahavior (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 106-110 
    Details
    ISSN: 0006-3592
    Keywords: inactivation ; thermal inactivation ; enzymes ; alcohol dehydrogenase ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A rapid method is developed to analyze the kinetics of thermal inactivation of enzymes that exhibit a nonlinear biphasic log(activity)-time relationship. Thermal destruction experiments on alcohol dehydrogenase from baker's yeast demonstrate the applicability of the method. The method is based on physical considerations (as opposed to mathematical curve fitting/regression methods) and also serves as a quick check of results obtained using nonlinear regression. It is superior to fitting nonlinear enzyme inactivation data by first-order kinetics or taking the initial and final slopes of the inactivation data. In fact, the method is of general validity and can be applied to any decay process that can be represented by a sum of exponentials. © 1996 John Wiley & Sons, Inc.
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    Mass transfer and temperature effects on substrate utilization in brewery granules (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 465-475 
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    ISSN: 0006-3592
    Keywords: anaerobic granules ; mass transfer ; temperature effect ; kinetics ; acetate ; propionate ; ethanol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Liquid film and diffusional resistances of brewery granules during acetate, propionate, and ethanol utilization were investigated. Substrate utilization rate increased with decreased granule size. Effectiveness factors for acetate, propionate, and ethanol were calculated by comparing the maximum rates of substrate utilization of whole granules (1.8 to 3.0 mm) and fine flocs (20 to 75 μm) derived by disrupting whole granules. For acetate, propionate, and ethanol, maximum specific substrate utilization rates (km′ g/g VS · d) for the flocs, were 5.11, 6.25, and 5.49, respectively, and half-velocity coefficients (Kg′ mM) were 0.45, 0.40, and 3.37, respectively. Calculated effectiveness factors were 0.32, 0.41, and 0.75 for acetate, propionate, and ethanol, respectively. The effect of temperature on substrate utilization was examined at 26°C, 31°C, and 37°C using acetate as sole carbon source. Utilization rates increased with temperature. Flocs were most sensitive to temperature, and whole granules were least affected. The behavior of flocs was well described by the Van't Hoff-Arrhenius equation. Effectiveness factors for acetate utilization by the granules were 0.36, 0.35, and 0.32 at 26°C, 31°C, and 37°C, respectively, indicating little effect of temperature. Based on these results, we conclude that both liquid film and diffusional resistances influenced the rate of substrate utilization in a UASB reactor with granular sludge. Temperature effects were much less important than diffusional limitations within the granules. © 1995 John Wiley & Sons, Inc.
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    Kinetics and mass transfer for lactic acid recovered with anion exchange method in fermentation solution (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 1-7 
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    ISSN: 0006-3592
    Keywords: anion exchange ; lactic acid ; kinetics ; mass transfer ; exchange isotherm ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An anion exchange method for lactic acid recovered from lactic acid-glucose solution in an ion-exchange membrane-based extractive fermentation system was examined. The exchange isotherms of anion exchange resins for lactic acid recovered were measured batchwise, and the exchange-desorption kinetics of lactic acid passing through the exchange column was investigated. The determined typical breakthrough and elution curves were measured and simulated by conventional mode. The mass transfer coefficients were identified by numberical method. The effects of the velocity of the fluid on the dynamics were studied. Aqueous NaOH solution was found to be the best solvent for elution. An experiment on anioun exchange from clarified lactic acid fermentation broth was carried out to obtain knowledge of the performance of the ion exchange system from a borth. The ion-exchange mass-transfer coefficient and efficiency from the fermentation broth is found to be lower when compared with aqueous solutions of pure lactic acid. The results show that the separation method with anion exchange resins may be used in the production of lactic acid by fermentation.© 1995 John Wiley & Sons, Inc.
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    Fundamental denitrification kinetic studies with Pseudomonas denitrificans (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 26-41 
    Details
    ISSN: 0006-3592
    Keywords: nitrate ; nitrite ; denitrification ; kinetics ; T effects ; pH effects ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fundamental kinetic studies on the reduction of nitrate, nitrite, and their mixtures were performed with a strain of Pseudomonas denitrificans (ATCC 13867). Methanol served as the carbon source and was supplied in excess (2:1 mole ratio relative to nitrate and/or nitrite). Nitrate and nitrite served as terminal electron acceptors as well as sources of nitrogen for biomass synthesis. The results were explained under the assumption that respiration is a growth-associated process. It was found that the sequence of complete reduction of nitrate to nitrogen gas is via nitrite and nitrous oxide.It was found that the specific growth rate of the biomass on either nitrate or nitrite follows Andrews inhibitory kinetics and nitrite is more inhibitory than nitrate. It was also found that the culture has severe maintenance requirements which can be described by Herbert's model, i.e., by self-oxidation of portions of the biomass. The specific maintenance rates at 30°C and pH 7.1 were found to be equal to about 28% of the maximum specific growth rate on nitrate and 23% of the maximum specific growth rate on nitrite. Nitrate and nitrite were found to be involved in a cross-inhibitory noncompetitive kinetic interaction. The extent of this interaction is negligible when the presence of nitrite is low but is considerable when nitrite is present at levels above 15 mg/L.Studies on the effect of temperature have shown that the culture cannot grow at temperatures above 40°C. The optimal temperature for nitrate or nitrite reduction was found to be about 38°C. Using an Arrhenius expression to describe the effect of temperature on the specific growth rates, it was found that the activation energy for the use of nitrate by the culture is 8.6 kcal/mol and 7.21 kcal/mol for nitrite. Arrhenius-type expressions were also used in describing the effect of temperature on each of the parameters appearing in the specific growth rate expressions. Studies on the effect of pH at 30°C have shown that the culture reduces nitrate optimally at a pH between 7.4 and 7.6, and nitrite at a pH between 7.2 and 7.3. © 1995 John Wiley & Sons, Inc.
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    A comparative study of the purity, enzyme activity, and inactivation by hydrogen peroxide of commercially available horseradish peroxidase isoenzymes A and C (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 655-662 
    Details
    ISSN: 0006-3592
    Keywords: horseradish peroxidase ; peroxide ; kinetics ; inactivation ; suicide substrate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Horseradish peroxidase (HRP) is a commercially important enzyme that is available from a number of supply houses in a variety of grades of purity and isoenzymic combinations. The present article describes a comparative study made on nine HRP preparations. Six of these samples were predominantly composed of basic HRP, pl 8.5, and three of acidic HRP, pl 3.5. Two of the basic preparations were of lower purity than the others. The apparent molar catalytic activity of basic HRP with 0.5 mMABTS and 0.2 mM H2O2 was around 950 s-1 (about 770 s-1 for the less pure samples) and with a 5 mM guaiacol and 0.6 mM H2O2 was about 180 s-1 for all the samples. A similar value (approximately 1000 s-1) was observed for acidic HRP but only at higher concentrations of ABTS (20 mM). With 20 mM guaiacol the molar catalytic activity of the acid isoenzyme was 65 s-1. The apparent KM for ABTS of the acidic isoenzyme was 4 mM whereas for the basic isoenzyme it was 0.1 mM. All the enzymes were inactivated by H2O2 when it was supplied as the only substrate. Under these conditions the partition ratio (r = number of catalytic cycles given by the enzyme before its inactivation), apparent dissociation constant (Kl), and apparent rate constant of inactivation (kinact) were about twice as large for the acidic samples (1350, 2.6 mM, 9 · 10-3 s-1) as for the basic (650, 1.3 mM, 5 · 10-3 s-1). The apparent catalytic constant (kcat) was 3-4 times larger, and the efficiency of catalysis (kcat/Kl) was double for the acidic isoenzyme, but the efficiency of inactivation (kinact/Kl) was similar. The data obtained provide useful information for those using HRP isoenzymes for biotechnological applications (e.g., biosensors, bioreactors, or assays). © 1996 John Wiley & Sons, Inc.
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    Kinetics of chromate reduction during naphthalene degradation in a mixed culture (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 52 (1996), S. 357-363 
    Details
    ISSN: 0006-3592
    Keywords: chromium ; chromate ; naphthalene ; reduction ; kinetics ; model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mixed culture of Bacillus sp. K1 and Sphingomonas paucimobilis EPA 505 was exposed to chromate and naphthalene. Batch experiments showed that chromate was reduced and naphthalene was degraded by the mixed culture. Chromate reduction occurred initially at a high rate followed by a decrease in rate until chromate reduction ceased. Chromate reduction decreased in the mixed culture when a lower ratio of S. paucimobilis EPA 505 to Bacillus sp. K1 was utilized. A kinetic model incoporating a term for the cell density ratio is proposed to describe chromate reduction in the mixed culture under both chromate limited and electron donor limited conditions. The validity of the model, and its parameter values, was verified by experimental data generated under a variety of initial population compositions and a broad range of chromate concentrations. The consistent result of experimental data with model predictions implies that the model is useful for evaluating the interactions and the use of mixed culture for chromate removal. © 1996 John Wiley & Sons, Inc.
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    Determinants and rate laws of growth and death of hybridoma cells in continuous culture (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 642-654 
    Details
    ISSN: 0006-3592
    Keywords: animal cell culture ; growth ; cell death ; kinetics ; autoinhibitor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental data from six hybridoma cell lines grown under diverse experimental conditions in both normal continuous and perfusion cultures are analyzed with respect to the significance of nutrients and products in determining the growth and death rates of cells and with respect to their mathematical modeling. It is shown that neither nutrients (glucose and glutamine) nor the common products lactic acid, ammonia, and monoclonal antibody can be generally assumed to be the clear-limiting or inhibiting factors for most of the cultures. Correspondingly, none of the unstructured models existing in the literature can be generally applied to describe the experimental data obtained over a relatively wide range of cultivation conditions as considered in this work. Surprisingly, for all cultures the specific growth rate (μ) almost linearly correlates with the ratio of the viable cell concentration (NV) to the dilution (perfusion) rate (D). Similarly, the specific death rate (kd) is a function of the ratio of the total cell concentration (Nt) to the dilution (perfusion) rate. These results strongly suggest the formation of not yet identified critical factors or autoinhibitors that determine both the growth and death rates of hybridoma cells. Based on these observations, simple kinetic models are developed for μ and kd which describe the experimental data satisfactorily. Analysis of the experimental data with the kinetic models reveals that under the current cultivation conditions the formation rate of the autoinhibitor(s) or the sensitivity of cell growth and death to the autoinhibitor(s) is mainly affected by the medium composition. Irrespective of the cell lines, cells grown on serum-containing media have almost the same model parameters, which are distinctively different from those of cells grown on serum-free media. Furthermore, in contrast to the prevailing view, kd is shown to positively correlate with μ if the effects of cell concentration and dilution (perfusion) rate are considered. Several important implications of these findings are discussed for the optimization and control of animal cell culture. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 642-654, 1998
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    Applicability of competitive and noncompetitive kinetics to the reductive dechlorination of chlorinated ethenes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 751-755 
    Details
    ISSN: 0006-3592
    Keywords: PCE ; chlorinated ethenes ; kinetics ; bioremediation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Reductive dechlorination of chlorinated ethenes has typically been modeled using standard Michaelis-Menten kinetic equations, implying that each dechlorination step is catalyzed by a unique biological factor. An alternative kinetic model is based on the assumption that all steps are mediated by a single factor. These two options are considered in the context of chlorinated ethene degradation by a previously characterized anaerobic culture. Competitive kinetics afford better chi-squared and visual fits of the data set tested. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 751-755, 1998
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    A theoretical equation describing the time evolution of the concentration of a selected range of substrate molecular weights in depolymerization processes mediated by single-attack mechanism endo -enzymes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 387-393 
    Details
    ISSN: 0006-3592
    Keywords: depolymerization ; kinetics ; endo -enzymes ; theoretical equation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Monitoring the time evolution of the concentration of a selected range of molecular weights of substrate, referred to as “detectable” substrate, has been used to determine endo-enzymic activities in polysaccharide depolymerizing processes. In the methodologies based on the use of dye-labeled substrates, the “detectable” substrate extends from a given molecular weight threshold downward. On the contrary, in the fluorescent probe-flow injection analysis methodology, initially developed to determine (1 → 3)-(1 → 4)-β-d-glucanase activities, the “detectable” substrate extends from a given molecular weight threshold upward. Assuming that the time evolution of the molecular weight distribution of the substrate follows the most probable distribution (the enzymic attack is random and its mechanism is single attack), a theoretical equation describing the time evolution of the concentration of “detectable” substrate (from a given molecular weight threshold upward or downward) has been deduced. This equation, Wd = Wo · (1 + αt) · e-αt, where Wd is the concentration of “detectable” substrate, Wo is the initial concentration of the substrate, t is the depolymerization time, and α is a parameter correlated through a hyperbola with the initial concentrations of enzyme and substrate and the Michaelis-Menten constant, Km, has been tested against different (1 → 3)-(1 → 4)-β-d-glucan/(1 → 3)-(1 → 4)-β-d-glucanase systems using the fluorescent probe-flow injection analysis methodology and Calcofluor as the fluorescent probe. The most important predictions of the theoretical equation, which allow accurate determination of both endo-enzymic activities and kinetic constants, have been experimentally confirmed. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 387-393, 1998.
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    A structured model of dual-limitation kinetics (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 683-689 
    Details
    ISSN: 0006-3592
    Keywords: dual limitation ; cofactor responses ; kinetics ; multiplicative model ; structured model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A structured model of substrate-utilization kinetics that encompasses dual-limitation conditions, caused by simultaneously low concentrations of the electron donor and the electron acceptor, is developed by incorporating the internal cofactor responses into the kinetic variables. The structured model is based on an assumption that the maximum specific electron-donor-oxidation rate (qmd) is not a constant, but is linearly controlled by the intracellular chemical potentials, log(NAD/NADH) and log(ATP/ADP · Pi). Determination of the kinetic parameters for the dual-limitation model, using experimental data from the companion article, verifies that qmd varies and demonstrates that the NAD/NADH ratio affects qmd in a positive direction; thus, an increase of the ratio increases the rate of electron-donor utilization. Because the internal NAD/NADH ratio rises with an increase in Sar the specific electron-donor-utilization rate is accelerated by high Sa. Since the ratio also increases as the specific electron-donor-utilization rate falls, the specific rate is intrinsically accelerated by the cofactor response when it becomes low due to a depletion of electron donor. Because the cofactor responses upon changes of the external substrate concentrations are systematic, the dual-limitation model can be expressed as a function of only external concentrations of electron donor and electron acceptor, which results in a multiplicative (double-Monod) form. Thus, dual limitation by both substrates reduces the overall reaction rate below the rate expected from single limitation by only one, the most severely limiting, substrate. © 1996 John Wiley & Sons, Inc.
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    Kinetic characterization of mass transfer limited biodegradation of a low water soluble gas in batch experiments - Necessity for multiresponse fitting (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 511-519 
    Details
    ISSN: 0006-3592
    Keywords: ethene ; kinetics ; biodegradation ; mass transfer ; multiresponse fitting ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method was developed to characterize the kinetics of biodegradation of low water soluble gaseous compounds in batch experiments. The degradation of ethene by resting Mycobacterium E3 cells was used as a model system. The batch degradation data were recorded as the progress curve (i.e., the time course of the ethene concentration in the headspace of the batch vessel). The recorded progress curves, however, suffered gas:liquid mass transfer limitation. A new multiresponse fitting method had to be developed to allow unequivocal identification of both the affinity coefficient, Kaff, and the gas:liquid mass transfer coefficient, Kla, in the batch vessel from the mass transfer limited data. Simulation showed that the Kaff estimate obtained is influenced by the dimensionless (volumetric basis) ethene gas:liquid partitioning coefficient (H). In the fitting procedure, Monod, Teissier, and Blackman biokinetics were evaluated for characterization of the ethene biodegradation process. The fits obtained reflected the superiority of the Blackman biokinetic function. Overall, it appears that resting Mycobacterium E3 cells metabolizing ethene at 24°C have, using Blackman biokinetics, a maximum specific degradation rate, vmax, of 10.2 nmol C2H4 mg-1 CDW min-1, and an affinity coefficient, Kaff.g, expressed in equilibrium gas concentration units, of 61.9 ppm, when H is assumed equal to 8.309. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 511-519, 1997.
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    A unified model describing the role of hydrogen in the growth of Desulfovibrio vulgaris under different environmental conditions (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 732-746 
    Details
    ISSN: 0006-3592
    Keywords: Desulfovibrio vulgaris ; hydrogen cycling ; kinetics ; thermodynamics ; modeling ; anaerobic ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A unified model for the growth of Desulfovibrio vulgaris under different environmental conditions is presented. The model assumes the existence of two electron transport mechanisms functioning simultaneously. One mechanism results in the evolution and consumption of hydrogen, as in the hydrogen-cycling model. The second mechanism assumes a direct transport of electrons from the donor to the acceptor, without the participation of H2. A combination of kinetic and thermodynamic conditions control the flow of electrons through each pathway. The model was calibrated using batch experiments with D. vulgaris grown on lactate, in the presence and absence of sulfate, and was verified using additional batch experiments under different conditions. The model captured the general trends of consumption of substrates and accumulation of products, including the transient accumulation and consumption of H2. Furthermore, the model estimated that 48% of the electrons transported from lactate to sulfate involved H2 production, indicating that hydrogen cycling is a fundamental process in D. vulgaris. The presence of simultaneous electron transport mechanisms might provide D. vulgaris with important ecological advantages, because it facilitates a rapid response to changes in environmental conditions. This model increases our ability to study the microbial ecology of anaerobic environments and the role of Desulfovibrio species in a variety of environments. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:732-746, 1998.
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    Respirometric assay for biofilm kinetics estimation: Parameter identifiability and retrievability (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 35-45 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; attached growth ; respirometry ; parameter estimation ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Currently, no fast and accurate methods exist for measuring extant biokinetic parameters for biofilm systems. This article presents a new approach to measure extant biokinetic parameters of biofilms and examines the numerical feasibility of such a method. A completely mixed attached growth bioreactor is subjected to a pulse of substrate, and oxygen consumption is monitored by on-line measurement of dissolved oxygen concentration in the bulk liquid. The oxygen concentration profile is then fit with a mechanistic mathematical model for the biofilm to estimate biokinetic parameters. In this study a transient biofilm model is developed and solved to generate dissolved oxygen profiles in the bulk liquid. Sensitivity analysis of the model reveals that the dissolved oxygen profiles are sufficiently sensitive to the biokinetic parameters - the maximum specific growth rate coefficient (⁁μ) and the half-saturation coefficient (Ks) - to support parameter estimation if accurate estimates of other model parameters can be obtained. Monte Carlo simulations are conducted with the model to add typical measurement error to the generated dissolved oxygen profiles. Even with measurement error in the dissolved oxygen profile, a pair of biokinetic parameters is always retrievable. The geometric mean of the parameter estimates from the Monte Carlo simulations prove to be an accurate estimator for the true biokinetic values. Higher precision is obtained for ⁁μ estimates than for Ks estimates. In summary, this theoretical analysis reveals that an on-line respirometric assay holds promise for measuring extant biofilm kinetic parameters. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 35-45, 1998.
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    Biodegradation of 1,1,1-trichloroethane by a carbon tetrachloride-degrading denitrifying consortium (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 393-399 
    Details
    ISSN: 0006-3592
    Keywords: denitrification ; biodegradation ; kinetics ; 1,1,1-trichloroethane ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A denitrifying consortium capable of degrading carbon tetrachloride (CT) was shown to also degrade 1,1,1-trichloroethane (TCA). Fed-batch experiments demonstrated that the specific rate of TCA degradation by the consortium was comparable to the specific rate of CT degradation (approximately 0.01 L/gmol/min) and was independent of the limiting nutrient. Although previous work demonstrated that 4-50% of CT transformed by the consortium was converted to chloroform (CF), no reductive dechlorination products were detected during TCA degradation, regardless of the limiting nutrient. The lack of chlorinated TCA degradation products implies that the denitrifying consortium possesses an alternate pathway for the degradation of chlorinated solvents which does not involve reductive dechlorination. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:393-399, 1998.
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    Rapid biocatalytic polytransesterification: Reaction kinetics in an exothermic reaction (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 428-437 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; polyesters ; bulk polymerization ; calorimetry ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biocatalytic polytransesterification at high concentrations of monomers proceeds rapidly and is accompanied by an increase in the temperature of the reaction mixture due to liberation of heat of reaction during the initial phase. We have used principles of reaction calorimetry to monitor the kinetics of polymerization during this initial phase, thus relating the temperature to the extent of polymerization. Rate of polymerization increases with the concentration of monomers. This is also reflected by the increase in the temperature of the reaction mixture. Using time-temperature-conversion contours, a differential method of kinetic analysis was used to calculate the energy of activation (∼15.1 Kcal/mol). © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:428-437, 1998.
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    Mixing and phase hold-ups variations due to gas production in anaerobic fluidized-bed digesters: Influence on reactor performance (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 36-43 
    Details
    ISSN: 0006-3592
    Keywords: anaerobic fluidized bed ; hydrodynamics ; biogas production ; kinetics ; model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of mixing and phase hold-ups on gas-producing fluidized-bed reactors was investigated and compared with an ideal flow reactor performance (CSTR). The liquid flow in the anaerobic fluidized bed reactor could be described by the classical axially dispersed plug flow model according to measurements of residence time distribution. Gas effervescence in the fluidized bed was responsible for bed contraction and for important gas hold-up, which reduced the contact time between the liquid and the bioparticles. These results were used to support the modeling of large-scale fluidized-bed reactors. The biological kinetics were determined on a 180-L reactor treating wine distillery wastewater where the overall total organic carbon uptake velocity could be described by a Monod model. The outlet concentration and the concentration profile in the reactor appeared to be greatly influenced by hydrodynamic limitations. The biogas effervescence modifies the mixing characteristics and the phase hold-ups. Bed contraction and gas hold-up data are reported and correlated with liquid and gas velocities. It is shown that the reactor performance can be affected by 10% to 15%, depending on the mode of operation and recycle ratio used. At high organic loading rates, reactor performance is particularly sensitive to gas effervescence effects. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 36-43, 1998.
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    Shift from growth to nutrient-limited maintenance kinetics during biofilter acclimation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 330-339 
    Details
    ISSN: 0006-3592
    Keywords: biofilter ; kinetics ; maintenance metabolism ; acclimation ; biomass ; nutrient limitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During long-term operation of a biofilter, the mandatory absence of net cell growth forces the cells into maintenance metabolism, which is of relatively low rate compared to substrate consumption during the active growth of the acclimation phase. A model based on this shift in metabolism can explain the postacclimation decrease in activity sometimes reported for biofilters. The cessation of growth can be caused by nutrient depletion in the bed. Postacclimation nutrient addition increases activity primarily by allowing a return to the high substrate consumption rate of active growth, and only secondarily helps raise bed activity because of the ultimately higher amount of biomass in the bed. Simulations incorporating the acclimation period and the role of maintenance metabolism predict about 4 logarithms of growth during acclimation of a hexane biofilter, which was confirmed experimentally. Changes in a biofilter's biomass during the acclimation phase can be estimated from substrate conversion data using two approximate methods. The first follows the cumulative amount of substrate converted and uses the estimated yield of cells from substrate during active growth to estimate the total biomass created. The second method follows a rate constant for conversion of substrate in the bed. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 330-339, 1997.
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