Xanthan Gum production from industrial wastes

Introduction: Xanthan gum is a polysaccharide whose unusual rheological properties contribute to its wide-range of industrial applications (e.g. suspending, stabilizing, thickening agente). Its synthesis by Xanthomonas campestris from glucose as carbon source makes its production more expensive for non-food purposes, such as its use in oil recovery. Therefore, the industrial waste use as substrate is a strategy to reduce this gum production cost. Thus, this study evaluated the glycerin from biodiesel production and oxidized biodiesel as substrate in the gum production, aiming at its application in drilling fluids. Methods: Assays were carried out in 50 mL of medium containing 2% substrate (oxidized biodiesel, glycerin or sucrose), supplemented with 0.01% urea and 0.1% KH2PO4, and X. campestris 629 at 28°C/250 min-1/120 h. Rheological data (apparent viscosity and shear rate) were fitted to the Ostwald-de-Waele model: μ = K (γ)n-1, using a regression analysis to ascertain the apparent viscosity (K, n and R2). FTIR gum analysis was measured in the spectral range between 4000-400 cm-1, 4 cm-1 resolution in KBr pellets, and TGA between 0-700°C (heating rate of 10°C/min in air atmosphere). Results: Alternative substrates showed potential for xanthan synthesis with yields of 7.23 and 12.89 g/L for glycerin and biodiesel, respectively. Rheologically, the gum from glycerin displayed a consistency index (K) of 650 mPa.s and flow rate (n) of 0.2068, while the gum from biodiesel, a K = 937.3 mPa.s = 0.61. All gums exibited a pseudoplastic behavior (n <1.0). Gum FTIR analysis indicated a spectral behavior analogous to that obtained from sucrose, indicative of chemical-structural similarity. The gum thermal degradation occurred above 400°C. Thermal resistance is a parameter related to the performance of drilling fluids. Conclusions: Therefore, these wastes have potential to be a cost-effective and promising alternative carbon sources for non-food grade xanthan gum production.