Plant mannans have β(1-4) linkages, occasionally with α(1-6) galactose branches, forming galactomannans.
An additional type is galactoglucomannan found in soft wood with a mixed mannose/glucose β(1-4) backbone.
The hydrolysis of the main mannan backbone is catalyzed by various enzymes including β-mannosidase, β-glucosidase, and β-mannase.
MOS by definition can be produced from either insoluble galactomannan or soluble glucomannan, although the latter type is more widely marketed.
[citation needed] From 'manna', produced by several species of tree and shrub e.g. Fraxinus ornus from whose secretions mannitol was originally isolated.