Bifidobacteria-accessible carbohydrates in milk

One of the most remarkable features of breast milk is its diversity and abundance of complex sugars (glycans), in particular human milk oligosaccharides (HMOs), which are indigestible to the infant and reach the colon intact. HMOs are preferred substrates for several species of gut bacteria and act as prebiotics, promoting the growth of beneficial intestinal flora and shaping the infant gut microbiome. Short-chain fatty acids, generated through the saccharolytic breakdown of HMOs by the gut microbiome, are critical for intestinal health. Bifidobacteria are frequently found as the most abundant colonizers in the gut of breast-fed infants, generally accounting for 50%–90% of the total bacterial population detected in the feces of breast-fed infants. This is believed to be due to their remarkable capacity to metabolize and consume HMOs. This chapter describes the current knowledge related to the genetic adaptation of particular members of the genus Bifidobacterium that enable them to metabolize various HMOs.