Lacto-N-tetraose (LNT) is a linear tetrasaccharide human milk oligosaccharide composed of four monosaccharide units arranged in a defined sequence: galactose (Gal), N-acetylglucosamine (GlcNAc), a second galactose, and glucose (Glc). These units are connected by β-glycosidic bonds in the order Galβ1-3GlcNAcβ1-3Galβ1-4Glc, giving LNT the chemical formula C26H45NO21.
Structure and Composition
The structure of LNT features lactose (Galβ1-4Glc) at the reducing end, extended by lacto-N-biose (Galβ1-3GlcNAc) at the non-reducing end. This composition makes LNT a major intermediate oligosaccharide found in human milk. All glycosidic linkages are β-configured, contributing to its biochemical stability and functional properties.
Biological Functions
Lacto-N-tetraose plays essential roles in infant nutrition and early-life development. It acts as a prebiotic molecule, selectively promoting the growth of beneficial gut microorganisms such as Bifidobacteria, key contributors to a healthy infant gut microbiome. LNT is also linked to immune system modulation and enhanced protection against pathogens, participating in the well-established protective effects of human breast milk.
Synthesis and Production
LNT can be produced through enzymatic or chemical synthesis. Modern synthetic strategies rely on glycosylation reactions using lactose-, galactose-, and glucosamine-derived donors and acceptors. Advances in metabolic engineering have also enabled microbial biosynthesis of LNT, supporting its integration into infant formula and functional food products.
Safety and Applications
Scientific assessments confirm the safety of Lacto-N-tetraose as an ingredient in foods, including infant formula. Its incorporation aims to better replicate the complex oligosaccharide profile of human milk, providing non-breastfed infants with bioactive components essential for gut and immune development.
In summary, Lacto-N-tetraose is a structurally defined and biologically active human milk oligosaccharide that supports infant gut microbiota maturation and immune system development, with growing applications in nutritional and food sciences.
