Adhesion of bifidobacteria to granular starch and its implications in probiotic technologies

Adhesion of 19 Bifidobacterium strains to native maize, potato, oat, and ba rley starch granules was examined to investigate links between adhesion and substrate utilization and to determine if adhesion to starch could be expl oited in probiotic food technologies. Starch adhesion was not characteristi c of all the bifidobacteria tested. Adherent bacteria bound similarly to th e different types of starch, and the binding capacity of the starch (number of bacteria per gram) correlated to the surface area of the granules. High ly adherent strains were able to hydrolyze the granular starches, but not a ll amylolytic strains were adherent, indicating that starch adhesion is not a prerequisite for efficient substrate utilization for all bifidobacteria. Adhesion was mediated by a cell surface protein(s). For the model organism s tested (Bifidobacterium adolescentis VTT E-001561 and Bifidobacterium pse udolongum ATCC 25526), adhesion appeared to be specific for alpha -1,4-link ed glucose sugars, since adhesion was inhibited by maltose, maltodextrin, a mylose, and soluble starch but not by trehalose, cellobiose, or lactose. In an in vitro gastric model, adhesion was inhibited both by the action of pr otease and at pH values of less than or equal to3. Adhesion was not affecte d by bile, but the binding capacity of the starch was reduced by exposure t o pancreatin. It may be possible to exploit adhesion of probiotic bifidobac teria to starch granules in microencapsulation technology and for symbiotic food applications.