Abstract:

A strain of Xanthomonas campestris was screened and cultured for the production of xanthan. Effects of xanthan
concentration, pH, sodium chloride content and temperature on viscosities were determined. Rheological behaviors, pyruvate
content, and molecular weight of xanthan were investigated for further application. The strain produced 28.4 g/L xanthan.
The viscosity of xanthan increased rapidly when the concentration was higher than 4.0 g/L, but remained stable in the pH
range of 3.0–10.0. The viscosity of 1.0 g/L xanthan was increased by 20% in response to an increase in NaCl concentration
from 10 to 70 g/L, but showed a decrease at high temperature (higher than 35 ℃). The xanthan contained 6.35% pyruvate
and had a viscosity-average molecular weight of 5.7 × 106 D. Coefficient and fluidity index of the xanthan prepared from
Xanthomonas campestris at different concentrations were 26.94 and 0.765 5 for 1.0 g/L, and 489.65 and 0.328 1 for 5.0 g/L,
respectively. In conclusion, this strain of Xanthomonas campestris has tremendous application potential.

Key words: Xanthomonas campestris, xanthan, viscosity, pseudo-plastic fluid, pyruvate content