Commensal Relationship of Three Bifidobacterial Species Leads to Increase of Bifidobacterium in Vitro Fermentation of Sialylated Immunoglobulin G by Human Gut Microbiota

Sialylated immunoglobulin G (IgG) is an important immunoglobulin in breast milk, but its effect on adult gut microbiota is not yet clear due to digestion by pepsin. Based on our previous IgG protecting study, effects of sialylated IgG on gut microbiota were investigated by in vitro anaerobic fermentation in the present study. It was found that the addition of sialylated IgG could significantly promote the growth of Bifidobacterium. Meanwhile, three bifidobacterial species B. bifidum CCX 19061, Bembidion breve CCX 19041, and B. longum subsp. infantis CCX 19042 were isolated. Furthermore, B. breve CCX 19041 and B. longum subsp. infantis CCX 19042 showed co-culture growth property with B. bifidum CCX 19061 in a sialylated IgG-based medium, which was also supported by changes of free monosaccharides and N-glycan structure. These findings suggest that the increase of Bifidobacterium in vitro fermentation is attributed to the commensal relationship of the three bifidobacterial species by utilizing sugars released from sialylated IgG.