ACTION OF TRICHODERMA-REESEI MANNANASE ON GALACTOGLUCOMANNAN IN PINE KRAFT PULP

The di-, tri-and tetrasaccharides formed during Trichoderma reesei end o-beta-D-mannanase treatment of pine kraft pulp were studied. The olig osaccharides in the hydrolysate were fractionated using size-exclusion , anion exchange and activated carbon chromatography. The primary sequ ence of the purified oligomers was determined by two-dimensional NMR t echniques. The T. reesei mannanase cleaves the beta-1,4-glycosidic lin kage of D-mannosyl residues attached either to D-mannose or D-glucose. The D-mannosyl residue may also be substituted by a D-galactosyl grou p. The main disaccharide produced was mannobiose, but a significant am ount of 4-O-beta-D-glucopyranosyl-D-mannopyranose (GlcMan) was also pr oduced. After extensive hydrolysis the main trisaccharides produced we re nosyl-[6-O-alpha-galactopyranosyl]-D-mannopyranose (Glc(1)Man(2)) a nd opyranosyl-4-O-beta-glucopyranosyl-D-mannopyranose (Glc(2)Man). Som e mannotriose yranosyl-4-O-beta-D-mannopyranosyl-D-mannopyranose (GlcM an(2)) and nosyl-[6-O-alpha-galactopyranosyl]-D-mannopyranose (Gal(1)G lcMan) were also detected in the hydrolysate. The structures of two te trasaccharides were studied. They appeared to be yranosyl-4-O-beta-D-g lucopyranosyl-D-mannopyranose (Glc(3)Man) and yranosyl-4-O-beta-D-gluc opyranosyl-D-mannopyranose (Glc-ManGlcMan). According to the results o btained, the galactoglucomannan in pine contains regions in which two or three glucose units are linked together, which further means that i t may contain regions with several successive mannose residues. The ga lactose side groups were found to be attached only to mannose. (C) 199 7 Elsevier Science B.V.