Mannan content

The main carbohydrate components of isolated bakers yeast cell-walls are glucan (29%) and mannan (31%). The proportions vary with the strains and culture conditions for example, a marked decrease of mannan content occurs in inositol-starved cells. The structure of the cell wall is not known with certainty, but electron microscopy reveals two distinct layers, and it is believed that the outside surface consists of a charged, phosphorylated mannan layer (see the article by Northcote and references therein). 

Those species classed as softwoods (coniferous) generally show a higher mannan content and a lower xylan content than do those classed as hard-... 

In order to equate the consumption of lead tetraacetate to the mannan content of the pulp, Steinmann and coworkers analyzed a series of pulps for mannan, by hydrolysis and subsequent precipitation of mannose phenyl-hydrazone. A satisfactory correlation was observed between the two methods. Since this work was restricted to a study of acetylation-grade pulps, which are generally low in mannan, the correlation between consumption of lead tetraacetate and mannan content did not extend beyond 2 % of mannan. Further studies on this method, to determine whether or not it can be applied to less refined pulps, would be of great interest. 

Evidence for a chemical linkage between cellulose and mannan, at least in softwood pulps, continues to accumulate. In this connection, Steinmann and coworkers have observed that, during the normal preparation of cellulose acetate, a considerable part of the xylan may be lost (30 to 60%), whereas the mannan content is not greatly affected. These authors suggest that this may indicate that the mannan is bound to the anhydroglucose chain. According to these workers, certain differences in properties of cellulose acetate prepared from different samples of cellulose can be explained if a mannan-to-cellulose bond actually does exist. However, it must be realized that no definitive proof has been presented of a mannan-to-cellulose linkage in any preparation of wood cellulose. 

When the mannan content of wood pulps, as determined by lead tetraacetate oxidation (see page 294), was plotted against the viscosity ratio, the relationship in Fig. 1 was obtained. The correlation coefficient of the regression line was calculated to be 0.81, which is significant at the 1 % level. Xylan and carboxyl groups were considered to play a less important role in anomalous viscosity, since it was observed that pulps having similar... 

Fig. 1.—Relationship Between the Mannan Content of the Wood Pulps and the Viscosity Ratios of Corresponding Cellulose Acetates. "...

The effect of alkaline treatment on the mannan content of wood pulps... 

The starting material was spruce-chips with a mannan content of 12.9% (2). The heat-fractionation of milled spruce-chips was performed in a closed vessel in a microwave oven (MLS 1200 Microwave workstation. Milestone) with 9.1 g dry weight of wood chips in 100 ml of water solution (1, 2). Prior to the heat-fractionation, the milled spruce chips were impregnated (soaked) in either water or water solutions of sodium hydroxide (0.025-2%), potassium hydroxide (0.05%) or sulfuric acid (0.05%) (2). The heat-fractionation was performed at different temperatures and times, ranging from 170° to 220° C and 2 to 20 minutes, respectively. The solids were discarded by filtration and the filtrates were analyzed further. 

Assay and Purification of p-Mannanases. p-Mannanase can be specifically measured in crude enzyme mixtures with a dye-labelled carob galactomannan substrate (6), This substrate has a galactose content high enough (23%) to impart solubility to the substrate, but sufficiently low as not to interfere with the action of p-mannanases on the D-mannan backbone. The soluble dye-labelled substrate is incubated with enzyme preparation under controlled conditions and the reaction is terminated and unreacted dyed polysaccharide precipitated by ethanol addition. 

Fio. 3.—Fractions of the D-Mannan Chain of Hot-water-soluble Carob Galactomannan (18% Content of D-Galactose) that Occur as Unsubstituted and Substituted D-Mannosyl... 

Fig. 2. Time courses of straw stem components for upgrading stems using 44 mg of P. ostreatus/g of stems at a moisture content of 1.6 g of H20/g of stems. ( ) glucan (A) xylan ( ) lignin with extractives ( ) ash (O) sum of galactan, arabinan,and mannan.

The Percentage Content of N-Acetyl Groups in (2-Acetamido-2-deoxy-D-gluco)-mannans from Yeasts, Based on Magnitude of NAc Signals in Proton-N.m.r. Spectra... 

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