Physicochemical and bioactive modifications of lotus root polysaccharides associated with probiotic fermentation

The physicochemical properties and bioactivities of lotus root polysaccharides (LRP) were investigated by examining the effects of probiotic fermentation. Five polysaccharides, namely LRP, LRP-Pl, LRPRh, LRPPa, and LRPAc, were extracted from unfermented and fermented lotus roots using Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus paracasei and Lactobacillus acidophilus, respectively. The results revealed that the yield of LRP-Ac (3.28 %) was 3.34 times higher than that of LRP (0.98 %), with its total sugar content and glucose content in the monosaccharide composition being the highest among the five polysaccharides. Probiotic fermentation led to an increase in Mw, as well as alterations in surface morphology and glycosidic bonds of LRPs, depending on the bacterial strains. Moreover, the five polysaccharides showed differences in antioxidant, α-amylase/α-glucosidase inhibitory, prebiotic, and macrophage-stimulating activities. Specifically, LRP-Pl exhibited the strongest DPPH radical scavenging ability; LRP-Rh showed the highest ABTS radical scavenging ability along with FRAP capacities; LRP-Ac possessed the greatest α-glucosidase inhibitory as well as prebiotic activities. However, the fermented polysaccharides showed relatively weak macrophage-stimulating ability compared to unfermented ones. Finally, the structure-activity relationship analysis revealed a close correlation between the chemical composition, Mw, and monosaccharide composition of LRPs and their bioactivities. These results are useful for the preparation of high-value LRPs.