Microbial xanthan gum production from alkali-pretreated rice straw

Xanthan is the first polysaccharide commercially produced by abacterial fermentation using simple sugars. In this study, rice straw was introduced as an inexpensive and widely available carbon source for microbial xanthan gum production. The production yield was improved by pretreatment with NaOH and NaHCO3. The pretreatment with 2 M sodium hydroxide was performed at 0 and 100 degrees C, and the pretreatment with 0.25, 0.5, and 1 M NaHCO3 was conducted at 120, 150 and 180 degrees C. The results showed that xanthan yield was increased up to five times in the case of pretreatment with NaOH at 100 degrees C as well as 1 M NaHCO3 at 180 degrees C. Although the temperature considerably influenced xanthan yield in the pretreatment with NaOH, the yield was not affected by temperature and concentration in the case of NaHCO3. The quality of the produced xanthan was compared with its commercial equivalent using thermogravimetric thermal analysis, differential thermal analysis, and Fourier transform infrared spectroscopy. The comparison showed that the quality of the produced xanthan was close to the commercial one. It was concluded that rice straw can be a promising substrate for xanthan gum production after the pretreatments.