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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1046-1052 
    ISSN: 0006-3592
    Keywords: fungus ; rheology ; morphology ; continuous culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aspergillus niger was grown in a 7-L chemostat at biomass levels of 7 to 9 gL-1; dilution rates of 0.03, 0.05, 0.075, and 0.009 h-1; and dissolved oxygen tensions of 7%, 12%, and 40% of air saturation. Broth rheological measurements were made on-line, while off-line image analysis was used to measure mycelial morphology, including characterization of mycelial aggregates (clumps). Under all conditions, more than 87% of the hyphase were in clumps, the shape of which determined the rheological characteristics of the broth. In particular, the power law consistency index could be correlated with the biomass concentration and the roughness factor of the clumps, which describes their hairiness. A decrease in specific growth rate decreased roughness, possibly due to changes in the amount of clump breakup. However, decreases of roughness with increasing dissolved oxygen tension might rather imply some effect on hyphal-hyphal interactions within the clumps. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0006-3592
    Keywords: Fusarium moniliforme ; hydrodynamics ; image analysis ; kinetic energy ; morphology stirred bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of two mixing geometries (at the same scale) with different flow energy distributions on the performance of the gibberellic acid fermentation and on the morphology of the producing fungus Fusarium moniliforme was investigated. Fermentations were performed using a turbine mixing system (TMS) and a counterflow mixing system (CMS), which were high and low power number mixing systems, respectively. Different agitator speed rate profiles were maintained to obtain equal specific power inputs to both mixing systems. Substantial differences in morphology and productivity of F. moniliforme were found. To investigate the causes of these differences, local values and spectra of the kinetic energy of flow fluctuations were measured during the fermentations using a stirring intensity measuring device (SIMD) and a frequency spectrum analyzer. Biomass and gibberellic acid concentrations were found to be higher in the TMS, where the energy distribution was less even, and Vi/here the main part of the energy was at small frequencies (large eddies). An automated image analysis method was used for quantitative characterization of F. moniliforme freely dispersed mycelia and clump morphology. A higher proportion of clumped mycelia with clumps of larger area, perimeter, and roughness was observed in the TMS. A correlation between the morphology and productivity was found, and TMS favored the development of more productive mycelia with longer and thinner hyphae. Introduced power was not a good parameter to characterize different impellers, even at a given scale. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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