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  • 1
    Electronic Resource
    Electronic Resource
    Xanthan batch fermentations: compared performances of a bubble column and a stirred tank fermentor (1990)
    Springer
    Bioprocess and biosystems engineering 5 (1990), S. 107-114 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Fermentations of Xanthomonas campestris, NRRL B-1459, were carried out in a bubble column fermentor (BCF) and in a stirred tank fermentor (STF) to allow comparison of representative variables measured during the microbial growth and the gum production. The microbial growth phase was described by a logistic rate equation where maximum cell concentration was provided by nitrogenous compounds balance. The average value of the maximum specific growth rate was higher in the bubble column (μ M =0.5 h−1) than in the stirred reactor (μ M =0.4 h−1). The upper values of xanthan yield (Y g-x =0.65 kg xanthan/kg glucose; Y O 2−x xanthan/kg oxygen) and specific production rate (q x =0.26 kg xanthan/kg biomass · h) were measured when the oxygen transfer coefficient was kept up above 80 h−1 in the STF fermentor. In the bubble column the fermentation achieved in the same culture medium lasts two times longer than in the stirred aerated tank; this was attributed to the low value of the oxygen transfer coefficient (K L a =20 h−1) at the beginning of the gum synthesis phase. The results obtained in the stirred tank were the basis to estimate the optimal biomass concentration which enables to achieve a culture in non-limiting oxygen transfer conditions. Nevertheless, the transfer characteristics were more homogeneous in the bubble column than in the stirred tank where dead stagnant zones were observed. This is of primary importance when establishing fermentation kinetics models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388188
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of oxygen transfer and carbon source composition on the growth of Corynebacterium melassecola (1995)
    Springer
    Bioprocess and biosystems engineering 13 (1995), S. 197-204 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Corynebacterium melassecola, a glutamate producing bacteria, has been cultivated in a 4-l batch aerated fermentor with glucose and fructose mixtures of various proportions as carbon sources and mineral ammonium as nitrogen source. Experimental results are analysed in order to obtain the specific rates and the conversion yields. A data reconciliation technique is used to manage with the experiments performed in similar conditions. The redundant experimental informations are used to test the carbon, nitrogen, available electrons, phosphorus and protons balances. The measurement of dissolved oxygen tension and volumetric oxygen transfer coefficient indicates that oxygen was never a limiting substrate in the experimental device though the oxygen demand was up to 70 mmoles/l.h and the heterogeneity of the liquid phase. The highest specific growth rate (0.59 h−1) and the highest biomass production yield (0.48 gX/gS) are obtained with glucose as the sole carbon source. These two parameters progressively decrease with the increase of the proportion of fructose in the medium down to 0.43 h−1 and 0.38 gX/gS on fructose so that the specific carbon uptake rate remains constant and equal to 0.04 C-mole/gX h. From a metabolic point of view, this decrease of the carbon conversion efficiency into cellular material is correlated to a lower carbon flux through the pentose pathway as the fructose proportion is increased. This is correlated with an accumulation of fructose 1,6-biphosphate which further activates the lactate deshydrogenase resulting to lactate production though the metabolism remains strictly aerobic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367254
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  • 3
    Electronic Resource
    Electronic Resource
    Intra- and extracellular concentrations of glutamate, lactate and acetate during growth of Corynebacterium glutamicum on different media (1997)
    Springer
    Journal of industrial microbiology and biotechnology 18 (1997), S. 312-318 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: Corynebacterium glutamicum; glutamate; intracellular concentrations; carbon fluxes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Corynebacterium glutamicum ATCC 17965 was cultivated in a 4-L batch aerated fermentor with glucose, fructose and mixtures of these two sugars in various proportions as carbon sources and with different concentrations of minerals and vitamins. A multilayer centrifugation technique was devised to obtain cell extracts in order to assess intracellular production of glutamate and partitioning between intracellular and extracellular spaces for lactate and acetate, the main by-products produced during the growth phase. Glutamate production increased with the proportion of glucose in the carbon source. The average value for the intracellular concentration of glutamate obtained with basic glucose medium was increased three-fold when initial concentrations of vitamins and minerals were increased four-fold. In this case, overall production of glutamate (16.3 mM) reached the highest value obtained. Production of acetate was weak on all media types (〈 1.6 mm). it was the same for lactate synthesis in media where glucose remained the major carbon source (〈 2.3 mm). production of lactate was significantly higher on media where fructose was the main carbon source (〉 10 mM to 60 mM). The increase in lactate production and the decrease in glutamate production were correlated to a modification of carbon flux distribution between the metabolic pathways as the fructose proportion was increased. An increase in the concentration of minerals favoured production of glutamate during growth. This was correlated with an increase in the NADPH,H+ production rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900386
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  • 4
    Electronic Resource
    Electronic Resource
    Conversion of radiant light energy in photobioreactors (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 1055-1066 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400616
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  • 5
    Electronic Resource
    Electronic Resource
    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
    Keywords: modeling ; kinetics ; cyanobacteria ; photobioreactors ; radiative transfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400709
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  • 6
    Electronic Resource
    Electronic Resource
    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
    Keywords: Corynebacterium ; intracellular flux ; metabolism network ; growth phase ; mixture of carbon sources ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    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
    Keywords: Modeling ; kinetics ; cyanobacteria ; photobioreactors ; Spirulina platensis ; mineral limitations ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400710
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of oxygen transfer and carbon source composition on the growth of Corynebacterium melassecola (1995)
    Springer
    Bioprocess engineering 13 (1995), S. 197-204 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Corynebacterium melassecola, a glutamate producing bacteria, has been cultivated in a 4-l batch aerated fermentor with glucose and fructose mixtures of various proportions as carbon sources and mineral ammonium as nitrogen source. Experimental results are analysed in order to obtain the specific rates and the conversion yields. A data reconciliation technique is used to manage with the experiments performed in similar conditions. The redundant experimental informations are used to test the carbon, nitrogen, available electrons, phosphorus and protons balances. The measurement of dissolved oxygen tension and volumetric oxygen transfer coefficient indicates that oxygen was never a limiting substrate in the experimental device though the oxygen demand was up to 70 mmoles/l.h and the heterogeneity of the liquid phase. The highest specific growth rate (0.59 h-1) and the highest biomass production yield (0.48 gX/gS) are obtained with glucose as the sole carbon source. These two parameters progressively decrease with the increase of the proportion of fructose in the medium down to 0.43 h-1 and 0.38 gX/gS on fructose so that the specific carbon uptake rate remains constant and equal to 0.04 C-mole/gX h. From a metabolic point of view, this decrease of the carbon conversion efficiency into cellular material is correlated to a lower carbon flux through the pentose pathway as the fructose proportion is increased. This is correlated with an accumulation of fructose 1,6-biphosphate which further activates the lactate deshydrogenase resulting to lactate production though the metabolism remains strictly aerobic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367254
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  • 9
    Electronic Resource
    Electronic Resource
    Dynamic model of a nitrifying fixed bed column: Simulation of the biomass distribution of Nitrosomonas and Nitrobacter and of transient behaviour of the column (1999)
    Springer
    Bioprocess engineering 20 (1999), S. 209-221 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A dynamic model for a fixed bed nitrifying column with recirculation of the liquid and gas phases was developed. Liquid RTD experiments demonstrated that the liquid phase was perfectly mixed inside the column. Hete- rogeneity of biomass distribution on the solid phase (beads) was represented by an N-tanks in series model, and a back-mixing term was set to account for the well-mixed liquid phase throughout the column. In autotrophic conditions, competition for oxygen is the cause of the spatial segregation of the two species. Nitrosomonas is concentrated on beads at the bottom of the bed whereas Nitrobacter is more widely distributed. This is consistent with biomass distribution results reported by Cox et al. [17] in a nitrifying fixed bed column. Nitrification takes place at the bottom of the column, always in oxygen gas-liquid mass transfer limiting conditions. Nevertheless, considering the whole process, nitrification is complete (〉98% of NH3 oxidised) and there is no oxygen limitation (the outlet dissolved oxygen concentration is not limiting). The dynamic behaviour of the column, in conditions set up to avoid biofilm diffusion limitation, was simulated for different NH3-load variations and oxygen shutdowns. The simulated behaviour of the column can be compared to results reported by Bazin et al. [16]. This confirms that the output transient nitrite peaks are higher when changes in the process conditions produce a rearrangement of biomass distribution in the fixed bed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009045
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  • 10
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330404
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