The genus Bifidobacterium possesses a unique fructose-6-phosphate phosphoketolase pathway employed to ferment carbohydrates.
Much metabolic research on bifidobacteria has focused on oligosaccharide metabolism, as these carbohydrates are available in their otherwise nutrient-limited habitats. Interestingly, infant-associated bifidobacterial phylotypes appear to have evolved the ability to ferment milk oligosaccharides, whereas adult-associated species use plant oligosaccharides, consistent with what they encounter in their respective environments. As breast-fed infants often harbor bifidobacteria-dominated gut consortia, numerous applications attempt to mimic the bifidogenic properties of milk oligosaccharides. These are broadly classified as plant-derived fructo-oligosaccharides or dairy-derived galacto-oligosaccharides, which are differentially metabolized and distinct from milk oligosaccharide catabolism.