Answer:
Lots of bacteria are present as the microflora of a baby's gut which helps it to extract the nutrition from mother's milk and also helps the baby to maintain a low number of pathogenic bacteria in its gut.
Some bacteria present in the baby gut release enzymes like glycoside hydrolase which helps baby to digest carbohydrate present in the mother's milk.
Bacteria like Bifidobacterium, Streptococcus, Staphylococcus are already present in breast milk which helps in making gut microflora of baby and this gut microflora helps in extracting nutrients from mother's milk.