Different Utilization of Oligosaccharides and Distribution of Several Genes Associated with Oligosaccharide Metabolism in Bifidobacterium longum

The growth of 9 strains isolated from probiotic products and 18 strains from human feces belonging to Bifidobacterium longum biotype longum on media containing glucose or one of three oligosaccharides (i.e. lactulose, fructooligosacchrides, raffinose) as the sole carbohydrate source was compared in pure cultures. The strains differed in their growth profiles when tested on different oligosaccharides. Almost all probiotic isolates showed markedly poor growth on the oligosaccharides, especially lactulose and raffinose, as compared to the fecal isolates. Subsequent PCR assays targeting several genes associated with oligosaccharide metabolism showed an apparent lack of the gene BL0275 in the probiotic isolates; BL0275 encodes endogalactanase that liberates galactotrisaccharides from galactans and galactooligosaccharides in the probiotic isolates. The evidence suggests that most, if not all, of the probiotic isolates of B. longum biotype longum have a poor ability to utilize oligosaccharides.