Solubility galactoglucomannans

It was pointed out that direct attachment of the D-galactose residues to the hexosan framework is only one possibility. It was observed that the D-galactosidic linkage is quite labile to acids. Polysaccharides of similar composition were isolated from western hemlock and redwood Sequoia sempervirens), and it was suggested that water-soluble galactoglucomannans may be of general occurrence in softwoods. 

The ratios of the D-hexoses (D-galactopyranose, D-glucopyranose, and D-mannopyranose) in D-galactoglucomannans differ some results are summarized in Table VI. The proportion of D-galactose varies widely the solubility of the polysaccharide in water increases with increasing content of this D-hexose. The related polysaccharides, D-glu-... 

The galactoglucomannan of the holocellulose was degraded by the mannanase. The reaction was slow, but conversion showed a steady increase. After 80 hr of incubation, about 25% of the mannan was transformed into water-soluble products (Table I, Column 10). This figure was calculated on the basis of the mannose, glucose, and galactose present in the acid hydrolysate (cf. Experimental). 

Obviously, Meier s results may equally well be interpreted in terms of a triheteropolymer galactoglucomannan. Glucomannans are well known for their insolubility in water and their limited solubility in certain aqueous alkalis, whereas galactomannans are water-soluble. A glucomannan and a galactomannan, if really present, should be separable. It also appears... 

As will be discussed later (see p. 473), the alkali-soluble glucomannans in softwoods have now been shown to be partially 0-acetylated in their native state. If the 0-acetyl groups in softwoods are associated only with the D-mannose-containing hemicelluloses, experimental data indicate that the galactoglucomannans must also carry 0-acetyl groups. This conclusion is strengthened by the fact that the extracellular galactoglucomannans are partly 0-acetylated. 

Willfor, S., Rehn, P., Sundberg, A. et al. (2003) Recovery of water-soluble acetyl-galactoglucomannans from mechanical pulp of spruce. Tappi J., 2 (11), 27-32. 

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