When a baby drinks milk, it does not only nourish the baby's own body. Some of the substances in this milk can also serve as food for the bacteria in the baby's gut. Several of them help form the “good bacteria”: the gut microbiome.
Researchers already know of sugars in breast milk that promote the development of certain bacteria. But other sugars remain attached to proteins. To benefit from them, a bacterium must first manage to detach them. This is precisely what a study published on November 2, 2026, has explained.
A mother breastfeeds her baby.
Helena Jankovičová Kováčová · Pexels
A team led by the University of Birmingham studied a bacterium called Bifidobacterium bifidum. It is one of the bacteria that can be found in infants’ intestines. Some of its strains have an enzyme called PNGaseA, which can separate sugars from the protein fragments to which they are attached.
An enzyme is a molecule that helps carry out a chemical transformation. This one has a particular feature: it works much better when the target protein has already been cut into small pieces. This is something that can happen during digestion, when food is gradually broken down.
To verify this, the scientists presented the enzyme with whole proteins, modified proteins and small fragments. They then measured the sugars released. The result: the small fragments were significantly easier for the enzyme to use, and therefore easier for the bacterium to exploit.
This helps explain how certain bacteria can find their food in a baby’s gut. Another interesting point is that these sugars attached to protein fragments are found in breast milk, but not in the infant formulas described by the researchers.
The researchers now hope to learn more about these substances in order to improve infant formulas in the future. In particular, they will need to determine how these sugars are used in a real intestine, and then check whether adding them provides a measurable benefit to the baby. The current study cannot yet answer this question.