H-1-NMR AND C-13-NMR CHARACTERIZATION OF THE DIGALACTOSYLMANNOPENTAOSE LIBERATED FROM LEGUME SEED GALACTOMANNAN BY BETA-MANNANASE ACTION

Incubation of Locust bean gum with an Aspergillus niger beta-D-mannana se released a wide variety of galactomannan oligomers. A single heptas accharide, digalactosylmannopentaose, was obtained from fractionation of the mixture by size exclusion chromatography. The purity and chemic al composition of the sample was demonstrated using mass spectrometry, high performance anion-exchange chromatography and monosaccharide com position analysis. The primary structure of this heptasaccharide was u nambiguously identified using 2D H-1 and C-13 homonuclear and heteronu clear NMR. A complete assignment of the H-1 and C-13 signals of this o ligomer was achieved, producing an NMR dataset that will be of importa nce in the primary structure elucidation of larger and more complex ga lactomannan oligomers.