Production of xanthan gum by Xanthomonas species using starch as carbon source

Aim. The main goal of the present study was to examine the possibility of using starch as the main substrate for microbial production of xanthan gum by Xanthomonas campestris and Xanthomonas pelargonii. Methods. The bacteria were cultivated on starch hydrolyzate and glucose (as a reference) at three different sugar concentrations of 20, 30, and 40 g/L. Samples were taken at different time intervals (24, 48, and 72 h) from cultivation broth and concentration of xanthan was determined. General linear regression method was employed to analyze the results. Results. For starch hydrolyzate and glucose, the highest xanthan concentration of 8.7 and 7.8 g/L, respectively, was achieved at 40 g/l of substrate concentration after 48 h for Xanthomonas campestris. For all substrate concentrations, maximum xanthan production was obtained after 48 h while prolonged cultivation time (72 h) reduced the concentration significantly. Generally, differences between product yields obtained in cultures containing glucose or starch hydrolyzate were not significant. Conclusion. This study showed that pure glucose can be replaced by inexpensive starch hydrolyzate in the process of fermentative xanthan production.