The mechanism of probiotic action of human milk N-glycome towards B. infantis ATCC 15697 and identification of the principal functional components.

Human milk N-glycome promotes the growth of Bifidobacterium longum subsp. infantis ATCC 15697. However, the action mode of, and the major functional components for, the bifidogenic function of human milk N-glycome remain unclear. In this study, we demonstrated that milk N-glycome was transferred in an intact form from culture into the bacterial cell and then decomposed intracellularly, evidenced by the following facts: (1) No UHPLC peak shift of N-glycome recovered from culture was observed. (2) No milk N-glycan specific monosugar was detected in culture supernatant. (3) High intracellular exoglycosidase activities were detected. (4) Fluorescently labeled N-glycans were found to be located intracellularly using Laser Scanning Confocal Microscopy (LSCM). Regarding the principal components identification, a novel sequential deglycosylation-based strategy was established. Degalactosylation, defucosylation-desialylation, and defucosylation-desialylation-degalactosylation treatments of human milk N-glycome showed that galactose-containing glycans were the principal components for the probiotic function of human milk N-glycome towards B. infantis ATCC 15697.