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  • Biochemistry and Biotechnology  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Comprehensive modeling of methanogenic biofilms in fluidized bed systems: Mass transfer limitations and multisubstrate aspects (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 725-736 
    Details
    ISSN: 0006-3592
    Keywords: biofilms ; anaerobic digestion ; wastewater treatment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A cognitive model for anaerobic digestion in fluidized bed reactors is developed. The general pathway of the process is divided into five main reactions performed by different bacterial groups. Molecular diffusion of each substrate involved in the reaction scheme is described. Effectiveness factor calculations are performed in steady state for each bacterial group taken into account in the process. The case of a single substrate removal is discussed, and optimal biofilm sizes are found. Sequential substrate removal is investigated, and different kinetic regimes are characterized. The influence of biofilm size and primary substrate removal is discussed in the case of standard concentrations in the liquid phase. This study shows that, according to the theoretical model the limiting step of the process may be different and depends in a large way on mass transfer effects. Finally, importance of biofilm size is compared for acidogenic and methano-genic steps: each reaction is found to be optimized for different biofilm thicknesses. This result may be of interest for design purposes and further dynamic modeling. Concluding remarks concerning the validation of the model are made, and a comparison to experimental data from the literature is presented. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480622
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  • 2
    Electronic Resource
    Electronic Resource
    Yeast suspension filtration: Flux enhancement using an upward gas/liquid slug flow - application to continuous alcoholic fermentation with cell recycle (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 47-57 
    Details
    ISSN: 0006-3592
    Keywords: crossflow filtration ; tubular mineral membrane ; slug flow ; flux enhancement ; yeast suspension ; alcoholic fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study deals with the use of an upward gas/liquid slug flow to reduce tubular mineral membrane fouling. The injection of air into the feedstream is designed to create hydrodynamic conditions that destabilize the cake layer over the membrane surface inside the filtration module complex. Experimental study was carried out by filtering a biological suspension (yeast) through different tubular mineral membranes. The effects of operating parameters, including the nature of the membrane, liquid and gas flowrates, and transmembrane pressure, were examined. When external fouling was the main limiting phenomenon, flux enhancements of a factor of three could be achieved with gas sparging compared with single liquid phase crossflow filtration. The economic benefits of this unsteady technique have also been examined. To investigate the possibility of long-term operation of the two-phase flow principle, dense cell perfusion cultures of Saccharomyces cerevisiae were carried out in a fermentor coupled with an ultrafiltration module. The air injection allowed a high and stable flux to be maintained over 100 h of fermentation, with a final cell concentration of 150 g dry weight/L. At equal biomass level, a twofold gain in flux could be attained compared with classical steady crossflow filtration at half the cost. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:47-57, 1998.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    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.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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