Optimization study of xanthan gum production using response surface methodology

The cultural conditions for xanthan gum production by Xanthomonas campestris were investigated and optimized by response surface methodology, to maximize cell and xanthan production in batch experiments using a synthetic broth (Luria-Bertani plus glucose, LBG) without pH control. The individual and interactive effects of three independent variables (agitation rate (100–600 rpm), temperature (25–35 °C), time of cultivation (24–72 h)) on xanthan gum and biomass production were studied, using a face-centered composite design of experiments. A second ordered polynomial model was fitted and optimum conditions were estimated. Overall optimization allowed us to point out an optimal range of the three independent variables. Optimal xanthan gum production was found at 600 rpm 30 °C at 72 h and biomass at 600 rpm, 25 °C at 72 h. Furthermore, the consumption of substrate (glucose) and the variation of pH during the fermentation as well as the molecular weight and the pyruvate content of the formed polysaccharide are reported.