Increasing thermal resistance of the exoplosaccharide produced by Xanthominas campestris in presence of calcium cation: biopolymer enhancement for application in petroleum industry

Xanthan is one of the well-known polysaccharides which its industrial production began in the last century and yet is used in water-based drilling fluids for drilling oil wells, as well as other environmental applications such as increasing the resistance of building materials in geotechnics, in biochemical composition of barriers to prevent the spread of water pollution and soil cover to combat air pollutant fine-dust. This microbial biopolymer reduces water mobility by increasing viscosity and decreasing permeability, and each xanthan molecule binds countless water molecules. Despite its resistance to various stresses, increased resistance to high temperatures is required in petroleum biotechnology and other man-made environmental infrastructure. In this study, the culture of Xanthomonas campestris was investigated in the presence of salts and the extracted biopolymer was treated with different concentrations of the salt. The experiments showed that sulfite, which is used as an agent to increase temperature resistance, had no significant effect. However, calcium chloride solution with a final concentration of 10,000 mg/L increased the thermal resistance and at 120°C the viscosity of the treated xanthan was more than 1500 centipoise and higher than that of the untreated 1% xanthan solution. Calcium cation increased the thermal resistance of xanthan even at concentrations lower than 1000 mg/L. The time of exposure to calcium cations was effective in increasing the thermal resistance. Addition of calcium ions to the culture of Xanthomonas campestris bacteria also had similar effects. This effect is promising for the environmental applications of xanthan, especially its use in the composition of water-based drilling fluids.