Xylan beechwood

On treatment with periodatd ion, straw and beechwood xylan oxidize rapidly.104 As with other polysaccharides, the oxidation comes to a more definite end point in solutions which are buffered to pH 4-5. While somewhat more than the theoretical amount of periodate ion is consumed, the reaction apparently proceeds uniformly with oxidative cleavage of the 2,3 carbon bond to produce the structure indicated in Figure 4. In the course of the reaction the xylan passes into solution. The optical rotation of the oxidized product is surprisingly high (co. 100°). 

Fungus grown in medium containing AFEX-pretreated bagasse at 50 °C. Fungus grown in medium containing beechwood xylan at 50 C. 

Ebringerova, A., Srokova, 1. (2007). Preparation of beechwood xylan surfactants by microwave-assisted transesterification. Workshop Production and functionalization of hemicelluloses for... 

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... 

About a quarter of the mannan in the sprucewood holocellulose seems to be accessible to the mannanase. More mannan can be hydrolyzed only when the second hemicellulose becomes at least partly dissolved. The remaining mannan—less than half the initial amount— appears to be removable only together with cellulose degradation. In beechwood holocellulose, most of the main hemicellulose—i.e., the xylan —can be hydrolyzed rather selectively by the sole action of xylanase. This phenomenon could be due to the different molecular size of the two hemicellulases, mannanase about 24 A, xylanase about 18 A (JO), resulting in better diffusing conditions for the xylanase. However, the porosity of the... 

Analyses of the hemicelluloses of woods indicate the presence of a high proportion of D-xylose residues in association with those of a methyl ether of a hexuronic acid.64 The first evidence for the chemical structure of such wood xylans came from the isolation of xylobiose, xylotriose,65 and the aldobiouronic acid 0-(4-0-methyl-a-D-glucosyluronic)-(l —> 2)-D-xylose acid (IX)22 from partial hydrolyzates of aspen wood. The role of such oligosaccharide fragments in wood xylans became more apparent as the result of a study of a xylan from European beechwood,26 in which it was shown... 

Chromogenlc substrates Ostazln Brilliant Red hydroxyethylcellulose (OBR-HEC), a soluble covalently dyed cellulose derivative, a substrate specific for endo-l,4-3-glucanases (cellulases) [4] Remazol Brilliant Blue xylan (RBB-X), a soluble covalently dyed beechwood 4-0-methyl-D-glucurono-D-xylan, a specific substrate for endo-l,4-B-xylanases [4]. Both substrates are available on request from Chemapol Ltd., Praha, Czechoslovakia. 

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