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  • 1
    Digitale Medien
    Digitale Medien
    Modelling Xanthomonas campestris batch fermentations in a bubble column (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 394-405 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Rate and yield expressions relating to biomass and xanthan formation and to nitrogen, glucose, and oxygen consumption were established for Xanthomonas campestris batch fermentations in a bubble column. Microbial growth was described by the logistic rate equation, characterized by a maximum specific growth rate μM = 0.5 h-1 and a maximum attainable cell concentration provided by nitrogenous compounds. With regard to carbon metabolism, the decrease with time in experimental yields and in the experimental specific rates of xanthan production and glucose assimilation demonstrated the inadequacy of the Luedeking-Piret model. These decreases were connected to the simultaneous drop in dissolved-oxygen tension observed during xanthan synthesis. The knowledge of metabolic pathways and energetic balance were used to establish the relationships between substrate utilization, ATP generation, and xanthan production. The model was structured by assuming the oxygen limitation of both the respiration rate and the efficiency of the oxidative phosphorylation mechanism (P/O ratio). Consequently, the specific rates and yield expressions became dependent on the dissolved-oxygen tension, i.e., of the volumetric oxygen transfer in the fermentor.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260330404
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  • 2
    Digitale Medien
    Digitale Medien
    Modeling growth and succinoglucan production by Agrobacterium radiobacter NCIB 9042 in batch cultures (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 65-74 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Succinoglucan ; Agrobacterium radiobacter ; Structured model ; ATP ; cofactors balances ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Wild-type Agrobacterium radiobacter NCIB 9042 has been cultivated in batch cultures on a synthetic medium which was adapted for growth and succinoglucan production. Experiments were carried out in a 4-L stirred-tank aerated reactor. Glucose, biomass, polysaccharide, protein, and inorganic- and organic-nitrogen concentrations were measured, and oxygen consumption and CO2 production rates were obtained by a gas-balance technique. Nitrogen balance shows that inorganic nitrogen is entirely recovered into proteins. The carbon balance is satisfied with in ±5%. Stoichiometric equations for biomass growth and succinoglucan synthesis were established. The biosyntheticpolymer pathways including ATP and cofactor consumption were investigated. From previous studies, a (P/O) value of 1.66 is selected for oxygen sufficient cultures. The actual ATP requirements of 25.4 mmol ATP/g succinoglucan (38.5 mol ATP/mol succinoglucan), determined by a metabolic analysis, is 2.39 times the stoichiometric value. Experimental results were modeled by a system of differential equations. The exponential growth phase was described by a nitrogen-limited Monod equation. Subsequent succinoglucan synthesis followed a slightly modified Luedeking-Piret relation partitioning internal and external polysaccharide. Experimentally determined coefficients are compared with published results for continuous culture of A. radiobacter NCIB 11883.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260380109
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  • 3
    Digitale Medien
    Digitale Medien
    A structured model for simulation of cultures of the cyanobacterium Spirulina platensis in photobioreactors: II. Identification of kinetic parameters under light and mineral limitations (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 826-834 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Modeling ; kinetics ; cyanobacteria ; photobioreactors ; Spirulina platensis ; mineral limitations ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A structured model for the culture of cyanobacteria in photobioreactors is developed on the basis of Schuster's approximations for radiative light transfer. This model is therefore limited to monodimensional geometries and kinetic aspects.Light-harvesting pigments play a crucial role in defining the profile of radiative transfer inside the culture medium and in controlling the metabolism, particularly the metabolic deviations induced by mineral limitations. Modeling therefore requires the biomass to be divided into several compartments, among which the light-harvesting compartment allows a working illuminated volume to be defined within the photobioreactor. This volume may change during batch cultures, largely decreasing as pigment concentration increases during growth but increasing as pigments are consumed during mineral limitation. This approach enables, in photobioreactors of simple parallelepipedic, geometries, kinetic parameters to be determined with high accuracy; this may then be extended to vessels of more complex geometries, such as cylindrical photobioreactors.The model is applied to controlled batch cultures of the cyanobacterium Spirulina platensis in parallelepipedic photobioreactors to assess its ability to predict the behavior of these microorganisms in conditions of light and mineral limitations. Results allowed the study of optimal operating condition for continuous cultures to be approached © 1992 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260400710
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  • 4
    Digitale Medien
    Digitale Medien
    Conversion of radiant light energy in photobioreactors (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 1055-1066 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The conversion of radiant light energy into chemical affinity by microorganisms in photobioreactors is examined. The kinetics of entropy production in the system is theoretically established from entropy and energy balances for the material and photonic phases in the reactor. A negative chemical affinity term compensated for by a radiant energy term at a higher level of energy characterizes photosynthetic organisms. The local volumetric rate of radiant light energy absorbed, which appears in the dissipation function as an irreversible term, is calculated for monodimensional approximations providing analytical solutions and for general tridimensional equations requiring the solution of a new numerical algorithm. Solutions for the bluegreen alga Spirulina platensis cultivated in photoreactors with different geometries and light energy inputs are compared. Thermodynambic efficiency of the photosynthesis is calculated. The highest value of 15% found for low radiant energy absorption rates corresponds to a maximum quantum yield in the reactor.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690400616
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  • 5
    Digitale Medien
    Digitale Medien
    A structured model for simulation of cultures of the cyanobacterium Spirulina platensis in photobioreactors: I. Coupling between light transfer and growth kinetics (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 817-825 
    Details
    ISSN: 0006-3592
    Schlagwort(e): modeling ; kinetics ; cyanobacteria ; photobioreactors ; radiative transfer ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The study of the interactions between physical limitation by light and biological limitations in photobioreactors leads to very complex partial differential equations. Modeling of light transfer and kinetics and the assessment of radiant energy absorded in photoreactors require an equation including two parameters for light absorption and scattering in the culture medium. In this article, a simple model based on the simplified, monodimensional equation of Schuster for radiative transfer is discussed. This approach provides a simple way to determine a working illuminated volume in which growth occurs, therefore allowing indentification of kinetic parameters. These parameters might then be extended to the analysis of more complex geometries such as cylindrical reactors. Moreover, this model allows the behavior of batch or continuous cultures of cyanobacteria under light and mineral limitations to be predicted. © 1992 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260400709
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  • 6
    Digitale Medien
    Digitale Medien
    Metabolic flux distribution in Corynebacterium melassecola ATCC 17965 for various carbon sources (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 177-189 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Corynebacterium ; intracellular flux ; metabolism network ; growth phase ; mixture of carbon sources ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The distribution of carbon in the metabolic network of a bacterial cell was estimated by a mass-balance-based intracellular flux computation method. It was applied to the growth phase of Corynebacterium melassecola, a glutamic acid producing bacterium, using experimental production yields of biomass, lactate and acetate measured during batch cultures on glucose, fructose, and various mixtures of both sugars. This flux computation method identifies the direction of the 86 reactions that ensure proper metabolic function during the growth phase of C. melassecola. Flux ratios allow comparison of calculated and relevant experimental yields. The results highlight the key influence of the biomass production yield YX-O2 on the overall distribution of carbon; the proportion of carbon drained in the pentose-P pathway fell from a value in the range of 54% to 47% on media containing glucose (YX-O2 = 1.75 to 1.56 g X/g O2) to 37% on fructose medium (YX-O2 = 1.36 g X/g O2). The highest maintenance requirement was calculated on fructose medium (Jm = 290 mol ATP/100 mol fructose) which must be connected to a lower efficiency of cell multiplication observed on this substrate. Another important result was that the significant decreases in experimental values of production yields and rates observed on fructose medium which were related to the operation of the FBPase. In particular, it was estimated that, as long as the proportion of glucose in the carbon source remains above 22% (78% fructose), the operation of the FBPase is not necessary and the bacteria exhibit behavior similar to that observed on glucose alone; this result is consistent with experimental observations. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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