Chemical and biological properties of the novel exopolysaccharide produced by a probiotic strain of Bifidobacterium longum

tBifidobacterium longum W11 is a commercialized probiotic that has an exopolysaccharide (EPS) layercovering its surface which could play a role in the beneficial properties attributed to the strain; thus, wehave carried out chemical and biological analyses of this polymer. The eps cluster putatively involved inthe polymer synthesis presented a unique structural organization not previously reported in bifidobac-teria. B. longum W11 produced a complex polysaccharide blend with the main component composedof glucose and galactose. An exhaustive structural analysis identified two different repeating units: onelinear [→6)--Galf-(1→3)--Galp-(1→] and one, more abundant, with the same backbone in which the-Galf is 5-substituted by a -Glcp unit. The antioxidant capability and the lack of toxicity of the wholeEPS W11 mixture, as well as some functional characteristics of the producing strain, such as the in vitroresistance to gastrointestinal conditions and the adhesion of colonocytes, were also determined.