Holocellulose delignified

For all boards of mechanical or "therraomechanical pulp, the rate of isothermal heat evolution after an initiation period was maximum and then decreased with reaction time. For boards of delignified pulp, i.e. of holocellulose and bleached kraft, this rate reached an intial plateau and then increased with time at temperatures above 200°C whereas it remained almost constant at lower temperatures. The following parameters are evaluated as a function of temperature ... 

For the delignified boards of holocellulose or bleached kraft this evaluation of the rate of heat release with time was not possible. 

Some hemicelluloses are partially extractable with water, but they are usually extracted with alkaline solutions following removal of lipids and lignin. Delignified plant material is termed, holocellulose. Neutralization of the alkaline extract effects precipitation of the more linear and less acidic hemicelluloses, termed the hemicellulose A [63100-39-0] fraction. The more acidic and more branched material, termed hemicellulose B [63100-40-3], is precipitated with ethanol (70%). Hemicellulose B types type are usually water-soluble after extraction. 

Avicelases or Cellobiohydrolase C - - Mannanase. The action of mannanase on delignified sprucewood holocelluloses that were treated with avicelase 1, avicelase 2, or cellobiohydrolase C for 48 hr gave similar degradation patterns. The rate of total degradation increased rapidly when the mannanase was added the rate was most pronounced in the case of avicelase 1 (Figure 4). 

The xylanase hydrolyzed about half the xylan in the sprucewood holocellulose. This is in the range of the xylan degradation obtained in former studies with delignified beechwood (7,10,22). Boutelje et al. (5) reported only 20-30% xylan hydrolysis of sprucewood holocellulose by a xylanase, even after repeated treatments. They used the same holocellulose and a xylanase isolated from the same commercial enzyme preparation as were used in the mannanase treatment referred to above. The holocellulose contained only a low xylan portion and very little arabinose this could be the reason for the inferior degradation rate, and hence it is not surprising that no free arabinose was detected, in contrast to what... 

After exhaustive washing in water, the delignified material is dehydrated in acetone, dissected into shives (groups of adhering fibers) and embedded in Spurr resin. This material is designated as holocellulose. 

Pectic material exists in all woods and often appears in holocellulose preparations, although the amount is small in completely delignified holocellulose. Anderson prepared holocellulose containing 2% of lignin (by the method of Wise ) from Douglas fir and Western hemlock, and extracted the pectic substances with dilute ammonium hydroxide. The... 

By taking apart the cell wall of a modified wood specimen and separating the cell wall components from one another, it is possible to determine the distribution of bonded chemicals in the cell wall polymer. It is more difficult to delignify modified wood than unmodified wood, which means that the lignin has been substituted 122, 127, 128). This is true for wood reacted with both acetic anhydride and methyl isocyanate. Table IX shows that the lignin component is always more substituted than the holocellulose components 128). This would indicate that the lignin is either more accessible for reaction than holocellulose or that it is more reactive than holocellulose. Lignin was found to be more reactive than cellulose toward acetylation 129). 

By examination of the spectra in Figure 5, it is clear that polysaccharides (holocellulose, peaks at 72 and 106 ppm) are dominant in the delignified humin in the upper layers of peat but diminish in relative concentration with depth. This trend was also observed in the spectra of humin in Figure 2. At depth, the polysaccharides are minor compared to the paraffinic carbons (peak at 30 ppm). Thus, the paraffinic structures in humin are resistant to sodium chlorite oxidation, and their relative increase in concentration with... 

Figure 6. Nitrogen in partially delignified holocellulose samples from methyl isocyanate-modified...

Different separation and purification procedures have been proposed to isolate hemicelluloses from different raw materials. Extraction of hemicelluloses from different resources has been studied since a long time ago. Isolation of hemicelluloses using cost efficient extraction methods would be beneficial to increase the utilization of hemicelluloses. Alkaline aqueous solutions and organic solvents have been used to extract hemicelluloses from the original or delignified wood [holocellulose] [1,9,21,25,31,33,34,5 7]. 

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