Structural characterization and bifidogenic activity of polysaccharide from Dictyophora indusiata

Dictyophora indusiata is an edible and medicinal fungi with various nutritious, especially higher in carbohydrates. In this work, polysaccharide from Dictyophora indusiate (DIP) was extracted by the hot-water, and four polysaccharide fractions (DIP0, DIP1, DIP2 and DIP3) were obtained using cellulose DE-52 column. The objective of this study was to investigate the structure and bifidogenic activity of four polysaccharide fractions from Dictyophora indusiate. Structure of DIP was evaluated by HPLC, FT-IR and SEM, and the results indicated that four polysaccharide fractions from Dictyophora indusiate were consisted of mannose, glucose and galactose with almost the same functional groups. Remarkably, the DIP3 had significant differences in monosaccharide compositions, which additionally contains glucuronic acid. In addition, DIP0 exhibited a three-dimensional network structure formed by crosslinked chains, while DIP1, DIP2 and DIP3 displayed the irregular flake structure. During the periods of fermentation in vitro, a strong increase of Bifidobacterium longum was observed in the presence of DIP0, DIP1 and DIP2. In particular, Bifidobacterium longum produced more acetic acid in the medium with DIP0 as the carbon source during the fermentation, probably due to the fact that DIP0 contained higher mannose and lower glucose. These results suggest that DIP0 promoted the growth of Bifidobacterium longum and its metabolic synthesis of acetic acid, which would provide necessary information for the prebiotic studies of DIP.