Microbial xanthan production from forage sorghum straw: Influence of substrate, strains, and process conditions on xanthan properties

Microbial production of xanthan gum from forage sorghum straw (FSS) was investigated. The important aspect investigated was the synthesis of xanthan gum using hemicellulose as a substrate (hemicellulose-derived xanthan), a process that has been relatively underexplored in the existing literature. Xanthomonas campestris ATCC 33913 and an isolated strain from orange peel, identified as X. axonopodis, were utilized for xanthan production. The FSS hydrolysate obtained by treatment under 120 °C for 30 min and overliming, yielded xanthan gum concentration of 7.1 g/L for X. campestris and 6.9 g/L for X. axonopodis. The lower molecular weights of xanthan gum produced from FSS (590 kDa for X. campestris and 550 kDa for the isolated X. axonopodis), compared to those from glucose suggest distinct advantages for specialized applications. Xanthan gum from FSS also possessed a higher ratio of acetate to pyruvate, ranging from 1.5:1 to 1.91:1 for X. axonopodis and from 1.33:1 to 1.75:1 for X. campestris. This characteristic renders it an attractive choice for certain applications in the food industry. By utilizing this strain, 11.71 g of hemicellulose-derived xanthan gum and 13.8 g of cellulose-derived xanthan gum per 100 g of FSS were obtained, indicating a conversion rate of 25.51 %.