A novel coupled fermentation system for low-molecular-weight xanthan gum with diverse biological activities

Xanthan gum (XG) is a bacterial exopolysaccharide widely used in various industries due to its stability and rheological properties. Low-molecular-weight xanthan gum (LXG) exhibits enhanced properties and broader applications, but current degradation methods are limited. This study introduces an innovative coupled fermentation system for the efficient production of LXG. Endo-xanthanase from Microbacterium sp. XT11 was expressed in Pichia pastoris GS115, exhibiting optimal activity at pH 6.0 and 40 °C, with broad pH tolerance. The optimized coupled fermentation system used bean sprouts juice as nitrogen source, the inoculation quantity of X. campestris: P. pastoris was 1: 3, and the pH was controlled at 6.0. In the bioreactor, the total sugar concentration reached 12.12 g/L, the reducing sugar concentration reached 5.32 g/L, and the endo-xanthanase activity increased to 1150.26 U/L, which were 2.13, 2.3, and 3.71 times higher than those at the shake flask level, respectively. The prepared LXG had a molecular weight of 1093 Da and a monosaccharide ratio of 2.0:1.57:0.89 (glucose, mannose, and glucuronic acid). Bioactivity analysis revealed its antioxidant and prebiotic properties, promoting the growth of beneficial intestinal microbiota and metabolite production. This suggests the potential of LXG as a functional ingredient in intestinal health-focused foods and supplements.