Mannan is a hemicellulosic polysaccharide primarily composed of D-mannose residues linked by β-(1→4) glycosidic bonds in its linear form. It is commonly found in plant seeds, yeast cell walls, and certain algal sources, with structural variations such as glucomannans (mannose–glucose copolymers) and galactomannans (mannans containing galactose side chains).

Structural Features

Yeast mannans exhibit a complex architecture featuring an α-(1→6)-linked mannose backbone with short α-(1→2) and α-(1→3) side chains. They also possess an outer chain of mannose oligosaccharides bound to proteins, forming mannoproteins that support yeast cell wall stability. In plant sources such as ivory nut and konjac, mannans are characterized by linear, high–molecular weight chains that confer strong water-binding and gel-forming properties. These structural attributes enable biological interactions, particularly with mannose receptors on immune cells.

Health and Immunomodulatory Effects

Mannan activates macrophages and dendritic cells through mannose receptor engagement, stimulating endocytosis, phagocytosis, and cytokine secretion to strengthen innate immune responses. It promotes gastrointestinal health by binding pathogenic bacteria such as E. coli, preventing adhesion, modulating gut microbiota composition, and acting as a prebiotic to reduce inflammation while enhancing intestinal barrier integrity. Additional documented benefits include hypolipidemic activity via lipoprotein clearance, antioxidant effects, and anti-tumor potential through metastasis inhibition.

Applications in Nutrition and Therapy

As mannan-oligosaccharides (MOS), it is widely used in animal nutrition to improve growth, immune function, and overall performance, while reducing the impact of mycotoxins. In human health, mannan supplements support weight management, cholesterol reduction, and immune enhancement. Its excellent biocompatibility also supports emerging uses in cosmetics, drug delivery systems, and other therapeutic applications.