Impact of 2′-fucosyllactose on adult gut microbiota composition and metabolome based on colonic fermentation and prebiotic quantitative evaluation

2′-Fucosyllactose (2′-FL), a predominant human milk oligosaccharide, is widely employed as a commercial infant prebiotic. Nevertheless, the benefits of 2′-FL on complex gut microbiota need further exploration. The modulation of 2′-FL on adult gut microbiota composition and metabolome, particularly short-chain fatty acids (SCFAs) and tryptophan metabolism, was investigated via colonic fermentation, single bacterial strains cultivation, and prebiotic activity scoring evaluation. The 2′-FL fermentation in a complex microbial community indicated promising effects, including an increase in Bifidobacterium levels and changes in metabolic levels of tryptophan, SCFAs, and vitamins. Correlation analysis of microbiota and metabolome highlighted a positive correlation between Bifidobacterium and metabolites derived from SCFAs and indole. Scoring formulas for bacterial growth and substrate utilization were introduced to compare the overall response of 15 bacterial strains from key genera that were identified by 16S rRNA profiling to several prebiotics. In the cultivation of single bacterial strains, 2′-FL was selectively used by Bifidobacteria infantis and Enterococcus faecalis and was not degraded by potential pathogenic strains. This selective promotion of probiotics by 2′-FL was observed according to the scoring results, as 2′-FL showed higher scores for bacterial growth and substrate utilization when compared to galacto-oligosaccharides and fucose. This study demonstrated beneficial bifidogenic effect of 2′-FL in an adult complex microbial community and the potential of scoring evaluation as a quantitative tool for measuring the prebiotic effects of different oligosaccharides.