Sustainable production and characterization of medium-molecular weight welan gum produced by a Sphingomonas sp. RW

Welan gum is widely used in food, concrete, and oil recovery for its excellent stability and unique rheological properties. This study describes an engineered Sphingomonas sp. RW strain deficient in the lyase gene (welR) and outlines its application in an industrial by-product fermentation strategy to produce welan gum. The yield of the engineered strain was enhanced to 25.11 ± 0.05 g/L, whereas the broth viscosity (2110 mPas) increased by 281.81%. The welan gum produced by Sphingomonas sp. RW was named medium-molecular weight welan gum (MMWG, ~350 kDa). FT-IR and monosaccharide composition analysis revealed that the MMWG was composed of l-mannose, l-rhamnose, glucuronic acid, and glucose (with mole ratios of 1:4.46:1.26:2.82). Significantly, MMWG had favorable hydroxyl radical scavenging activity and emulsifying capacity. These results provide a strategy for cost-effective welan gum production and enrich the properties of welan gum with different molecular weight.