Production of xanthan gum using immobilized Xanthomonas campestris cells: Effects of support type

The aim of this study was to compare the biofilm production of xanthan gum via immobilization of Xanthomonas campestris cells on different types of support, i.e. smooth small pore size metal support (N1), wavy large pore size metal support (N2) and plastic support (N3), and calcium alginate beads (N4), in a batch condition during 72 h fermentation. The results showed that the recovery of xanthan gum was increased by employing supports. The xanthan recovery was similar to 8 and 6 g/L for biofilms N3 and N2, respectively. The chemical structure of xanthan gum produced herein was confirmed by Fourier transform infrared spectrometry and proton nuclear magnetic resonance. Thermal analysis of xanthan using thermo gravimetric analysis gum indicated two fractures which attributed to dehydration and volatile compounds evaporation and degradation of the polysaccharide backbone. Rheological tests exhibited that the G' values were higher than the G '' values for all frequency, showing high elasticity of the xanthan gum. Furthermore, shear stress vs shear rate data was fitted to the rheological models of power law, Bingham and Casson which indicated the pseudoplastic behavior of xanthan gum solution. Increasing the shear rate from 3.84 to 176.64 (s(-1)) reduced the apparent viscosity from 2000 to 26 mPa.s.