Dynamics of Structural and Functional Changes in Gut Microbiota during Treatment with a Microalgal β-Glucan, Paramylon and the Impact on Gut Inflammation

Previously, we have shown that oral administration of yeast derived β-1,3/1,6-d-glucan enhances immune regulation and alters the composition of the gut microbiota. However, it is not known if other structurally distinct β-glucans have similar properties. Here, using C57BL/6 mice, we show the potential of a microalgae derived β-1,3-d-glucan, paramylon (PM), in shaping the gut microbiota and modulating the susceptibility to colitis. The community structure within the gut microbiota showed progressive changes including selective enrichment of specific communities and lowered community richness and diversity during prolonged oral treatment with PM. Compared to control mice, the gut microbiota of PM-treated mice had significantly higher abundance of Verrucomicrobia and lower abundance of Firmicutes. Specific taxa that were significantly more abundant in PM-treated mice include Akkermansia muciniphila and several Bacteroides members. Predictive functional analysis revealed overrepresentation of carbohydrate metabolism function in the fecal microbiota of PM recipients compared to controls, and this function was linked to Bacteroides spp. Prolonged pretreatment with PM not only diminished susceptibility to dextran sulfate sodium induced colitis severity, but also caused enhanced immune regulation. Overall, this study demonstrates the prebiotic properties of PM and the potential benefits of its prolonged oral consumption to gut health.