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  • 1985-1989  (2)
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Materialart
Erscheinungszeitraum
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  • 1
    Digitale Medien
    Digitale Medien
    Rheological characterization of xanthan fermentation broths and their reconstituted solutions (1989)
    Springer
    Bioprocess and biosystems engineering 4 (1989), S. 113-117 
    Details
    ISSN: 1432-0797
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Two strains of X. campestris from a collection and a wild strain isolated from infected cabbage were cultured in a defined medium in a 25 dm3 fermenter. The rheological characteristics of the broth were measured using a Weissenberg rheogoniometer. The rheological behaviour over a wide range of shear rates could be described with the power law model and a yield stress was obtained using the Herschel-Bulkley equation. As expected, the broth's flow behaviour is highly influenced by gum concentration. In general, the rheological parameters during the fermentations varied within the following ranges: K (2–210 dyn-sn/cm2), n (0.2–0.9), τ y (0.02–50 dyn/ cm2), with strain 1459 reaching the maximum values as well as the highest gum concentration. Differences in flow behaviour could be associated with different molecular configurations of the polymers produced by the different strains. Heat treatment of the broths change the rheological characteristics, increasing K and decreasing n. Reconstituted solutions of all sterilized gums exhibited similar rheological characteristics and, at low concentrations, also similar to those of a commercial xanthan.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00369759
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Diffusion of sucrose in xanthan gum solutions (1989)
    Springer
    Bioprocess and biosystems engineering 4 (1989), S. 265-273 
    Details
    ISSN: 1432-0797
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Molecular diffusion of solutes, like sucrose in the xanthan gum fermentation, is important in order to understand the complex behavior of mass transfer mechanisms during the process. This work was focused to determine the diffusion coefficient of sucrose, a carbon source for xanthan production, using similar sucrose and xanthan concentrations to those occurring in a typical fermentation. The diaphragm cell method was used in experimental determinations. The data showed that diffusion coefficient of sucrose significantly decreases when xanthan gum concentration increases. Theoretical and semiempirical models were used to predict sucrose diffusivity in xanthan solutions. Molecular properties and rheological behavior of the system were considered in the modeling. The models tested fitted well the behavior of experimental data and that reported for oxygen in the same system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00368901
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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    Artikel (Nationallizenzen)
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