Viscous behaviour of xanthan aqueous solutions from a variant strain of Xanthomonas campestris

Abstract

Xanthan gum produced by a variant strain of Xanthomonas campestris isolated in our laboratory (México) and subjected to a defined downstream process was characterized by low shear viscometry in the dilute regime. The downstream process included an enzymatic treatment. Chemical analysis of the native xanthan were also performed. Xanthan solutions from a commercial source were characterized for comparison purposes. The chemical results indicated that the native xanthan had a higher acetyl/pyruvic ratio. Nevertheless, both products showed to have similar intrinsic viscosities. A linear functionality in the reciprocal of the square root of the ionic strength was observed for the intrinsic viscosity. In general, the results showed good agreement with the literature in terms of the critical concentration ( C∗), linearity of both the Huggins and Kramer equations, and dependence of the intrinsic viscosity on the ionic strength. In the low ionic strength range, deviations from linearity in the Huggins equation were observed and these were explained by considering the polyelectrolyte nature of xanthan solutions. The results suggest that the native xanthan produced with the new strain is comparable to the xanthan from the commercial source.