Two-step economical welan gum production by Sphingomonas sp. HT-1 from sugar industrial by-products

A two-step fermentation strategy using glucose mother liquor (GML) for cell growth and xylose mother liquor (XML) for welan gum synthesis was used to alleviate uneconomic welan gum fermentation. This study revealed: (1) optimal initial GML concentration was 11.7 g/L (10 g/L sugars contained); (2) optimal XML feeding strategy was pseudo-exponential fed-batch and feeding time was 12th h–54th h, amounting to 25.7 g/L XML (20 g/L sugars contained); and (3) in a 7.5-L bioreactor, welan gum concentration was 22.68 ± 0.50 g/L and its yield reached 0.756 g/g sugars with trace residual sugars. Compared with the cost of batch fermentation using glucose as sole carbon source, the final carbon source costs decreased by 61.40% and the welan gum yield increased by 50%. GML and XML can be used as inexpensive carbon sources for welan gum production with higher yield, giving them industrial application potential to produce value-added chemicals.