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  • 1
    Electronic Resource
    Electronic Resource
    Growth and substrate consumption of Nitrobacter agilis cells immobilized in carrageenan: Part 2. Model evaluation (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 232-240 
    Details
    ISSN: 0006-3592
    Keywords: immobilized cell growth ; Nitrobacter ; biomass profile ; model evaluation ; nitrification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model that predicts substrate and biomass concentration profiles across gel beads and from that the overall substrate consumption rate by the gel beads containing growing cells was evaluated with immobilized Nitrobacter agilis cells in an airlift loop reactor with oxygen as the limiting substrate. The model predictions agreed well with the observed oxygen consumption rates at three different liquid phase oxygen concentrations. Image analysis showed that 90% of the immobilized cells after 42 days of cultivation was situated in the outer shells in a film of 140 μm, while the bead radius was about 1 mm. The maximum biomass concentration in the outmost film of 56 μm was 11 kg · m-3 gel.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380304
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of diffusion limitation on immobilized nitrifying microorganisms at low temperatures (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 1-9 
    Details
    ISSN: 0006-3592
    Keywords: nitrification ; immobilized cells ; activation energy ; diffusion limitation ; temperature ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Activation energies of suspended and immobilized nitrifying bacteria were determined and compared to determine if diffusion limitation results in decreased sensitivity for temperature. The activation energy for the respiration activity of suspended Nitrosomonas europaea and Nitrobacter agilis was found to be 86.4 and 58.4 kJ mol-1, respectively. The activation energy for oxygen diffusion in the support material, κ-carrageenan, determined from the effect of temperature on the effective diffusion coefficient (D), was 17.2 kJ mol-1. Consequently, the apparent actvation energy of diffusion limited cells should be lower. It was indeed shown that due to the effect of diffusion limitation and to temperature effects on the Monod constant Ks, the immobilized-cell activity was less sensitive to temperature. The apparent activation energy for immobilized Ns. europaea was between 28.6 and 94.2 kJ mol-1 and for immobilized Nb. agilis between 1.4 and 72.9 kJ mol-1, depending on the oxygen concentration and temperature. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450102
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Death rate in a small air-lift loop reactor of vero cells grown on solid microcarriers and in macroporous microcarriers (1996)
    Springer
    Cytotechnology 21 (1996), S. 45-59 
    Details
    ISSN: 1573-0778
    Keywords: air lift ; macroporous ; microcarrier ; shear ; sparging ; Vero cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The death rate of Vero cells grown on Cytodex-3 microcarriers was studied as a function of the gas flow rate in a small air-lift loop reactor. The death rate may be described by first-order death-rate kinetics. The first-order death-rate constant as calculated from the decrease in viable cells, the increase in dead cells and the increase in LDH activity is linear proportional to the gas flow rate, with a specific hypothetical killing volume in which all cells are killed of about 2·10−3 m3 liquid per m3 of air bubbles. In addition, an experiment was conducted in the same air-lift reactor with Vero cells grown inside porous Asahi microcarriers. The specific hypothetical killing volume calculated from this experiment has a value of 3·10−4 m3 liquid per m3 of air bubbles, which shows that the porous microcarriers were at least in part able to protect the cells against the detrimental hydrodynamic forces generated by the bubbles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00364836
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Oxygen gradients in small and big sparged insect-cell bioreactors (1996)
    Springer
    Cytotechnology 20 (1996), S. 231-238 
    Details
    ISSN: 1573-0778
    Keywords: air lift ; animal cell ; bubble column ; design ; oxygen gradients ; scaleup ; stirred vessel ; CSTR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Conclusions It should be clear from the above that the calculations described here are at best rough estimations yielding order-of-magnitude values. Even though, the following general conclusions can be drawn. The gradients in stagnant layers surrounding the particles which are characteristic for animal-cell bioreactors are relatively small as compared to the gradients which can be expected in the bulk-liquid phases of the three bioreactors considered, in particular to the gradients in the stagnant layer surrounding the air bubbles. It can be concluded that under almost all circumstances gradients are likely to exist and can be very steep in larger vessels and in particular at high cell densities. The effects of gradients, however, are largely unknown; therefore research on the effects of gradients on specific and volumetric productivities and product quality seems to be an interesting area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350403
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Death rate in a small air-lift loop reactor of vero cells grown on solid microcarriers and in macroporous microcarriers (1997)
    Springer
    Cytotechnology 23 (1997), S. 61-75 
    Details
    ISSN: 1573-0778
    Keywords: air lift ; macroporous ; microcarrier ; shear ; sparging ; Vero cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The death rate of Vero cells grown on Cytodex-3 microcarrierswas studied as a function of the gas flow rate in a smallair-lift loop reactor. The death rate may be described byfirst-order death-rate kinetics. The first-order death-rateconstant as calculated from the decrease in viable cells, theincrease in dead cells and the increase in LDH activity islinear proportional to the gas flow rate, with a specifichypothetical killing volume in which all cells are killed ofabout 2.10-3m3 liquid per m3 of air bubbles.In addition, an experiment was conducted in the sameair-lift reactor with Vero cells grown inside porous Asahimicrocarriers. The specific hypothetical killing volumecalculated from this experiment has a value of 3.10-4m3 liquid per m3 of air bubbles, which shows thatthe porous microcarriers were at least in part able to protectthe cells against the detrimental hydrodynamic forcesgenerated by the bubbles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/B:CYTO.0000010399.23373.65
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    Paper (German National Licenses)
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