Enzymatic synthesis of oligodextran with prebiotic potential by a recombinant dextransucrase from Latilactobacillus...

Oligodextran exhibits considerable prebiotic potential and holds significant commercial promise for food and clinical applications. To facilitate its efficient production, the dextransucrase (Dex) gene from Latilactobacillus sakei L3 was heterologously expressed in Escherichia coli BL21(DE3). The recombinant enzyme demonstrated optimal activity at pH 5.0 and 30 °C, with its activity enhanced in the presence of Ca²⁺ or Mn²⁺ and inhibited by Cd²⁺, EDTA, and surfactants. Using 500 mM sucrose as the substrate, the Dex produced a polysaccharide (designated L3 OEPS) with a molecular weight of 5882 Da. Monosaccharide composition analysis confirmed L3 OEPS was composed exclusively of glucose. Structural characterization revealed a backbone predominantly consisting of α-1,6-glycosidic linkages with minor α-1,3-glycosidic branching. In vitro simulated digestion models showed that L3 OEPS resisted degradation by salivary, gastric, and small intestinal fluids. Conversely, during in vitro fecal fermentation, L3 OEPS was partially utilized by gut microbiota, leading to increased levels of acetic and propionic acids, particularly after 24 h. Furthermore, L3 OEPS modulated the gut microbial community structure, enhancing the abundance of beneficial genera such as Megamonas and Bifidobacterium to an extent comparable to inulin. These findings suggest that L3 OEPS holds promise as a novel prebiotic for improving gut health.