Bioprocess Engineering

, Volume 4, Issue 3, pp 113–117

Rheological characterization of xanthan fermentation broths and their reconstituted solutions

  • E. Galindo
  • B. Torrestiana
  • A. Garcia-Rejón
Originals

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), τy(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.

List of Symbols

Di m

impeller diameter

Dt m

tank diameter

A, B

constants in equation (4) of Thompson and Ollis [4]

K dyn-sn/cm2

consistency index

n

flow behaviour index

τ dyn/cm2

shear stress

\(\dot y\) s−1

shear rate

τy dyn/cm2

yield stress

KHB

Herschel-Bulkley equation constant

NHB

Herschel-Bulkley equation constant

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Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • E. Galindo
    • 1
  • B. Torrestiana
    • 1
  • A. Garcia-Rejón
    • 2
  1. 1.Dpto. de Bioingeniería Centro de Investigación sobre Ingeniería Genética y BiotecnologíaUniversidad Nacional Autónoma de MéxicoMéxico
  2. 2.Instituto de Investigaciones en MaterialesUniversidad Nacional Autónoma de MéxicoMéxico, D. F.
  3. 3.IMRI/NRC-CanadaBouchervilleCanada

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