Prebiotic Galactooligosaccharide Metabolism by Probiotic Lactobacilli and Bifidobacteria.

Galactooligosaccharides (GOS) are bifidogenic and lactogenic prebiotics; however, GOS utilization is strain dependent. In this study, commercially available bifidobacteria and lactobacilli probiotic strains were evaluated for growth in the presence of GOS. Several bifidobacteria and lactobacilli grew on GOS; however, the specific GOS oligomers utilized for growth differed. A subset of probiotic bifidobacteria and lactobacilli revealed three different GOS utilization profiles delineated by the degrees of polymerization (DP) of GOS: (1) utilization of 2 DP GOS, (2) utilization of <= 3 DP GOS, and (3) utilization of all DP GOS. Specifically, Lactobacillus acidophilus NCFM (LA_NCFM) was found to efficiently consume all GOS oligomers. Extracellular beta-galactosidase activity in the cell-free supernatant of LA_NCFM correlated with accumulation of galactose. In a LacL-deficient LA_NCFM strain, GOS utilization was abolished. This is the first report of LacL's role in GOS metabolism in LA NCFM. In vitro GOS utilization should be considered when GOS are delivered with probiotic bifidobacteria and lactobacilli.