Comparison of the Immunopotentiating Activity with Structural Characteristics among Water-soluble Polysaccharides Isolated from the Genus Bifidobacterium

The whole cells (WC) of three strains of bifidobacteria, Bifidobacterium adolescentis M101-4 (M101-4), B. pseudocatenulatum MBL8320 (MBL8320) and B. catenulatum MBL8318, were transformed into water-soluble and insoluble fractions (SF and IF, respectively) having mitogenic activity in murine splenocytes assay in vitro. A soluble high-molecular weight fraction (SHF) with mitogenic activity was successfully isolated from the SF by the following 6-step procedure: proteinase K treatment, ultrafiltration through a 50 kDa cut-off membrane filter, anion-exchange chromatography, dialysis, ultrafiltration through a 6 kDa cut-off membrane filter, and gel-filtration chromatography. The SHF obtained from the three strains were found to consist of polysaccharides containing -4Gal p 1-(and/or -5Gal f 1-) and -6Glc p 1- as the major residues, and Gal f 1- and -6Gal f 1- as characteristic galactofuranosyl residues by their analytical data. β- Glucosidase digestion of the high-molecular weight fractions after proteinase K treatment led to a decrease in the mitogenic activity for splenocytes, suggesting that β-glucosyl residue in the polysaccharides may play an important role in immunopotentiating activity.