Xylan degradation

The substitution pattern of arabinosyl side chains in AX from cereal flours and bran, based on the structural analysis of ohgomer fragments produced by xylan-degrading enzymes of known mode of action, was described by several authors [60-63], and various structural models were created [39,60]. fii a recent study [64] on the fine structure of wheat flour AX, a method was... 

Den Haan, R. Van Zyl, W. H. (2003). Enhanced xylan degradation and utilisation by Pichia stipitis overproducing fungal xylanolytic enzymes. Enzyme and Microbial Technology, Vol. 33, 5, (October 2003), pp. (620-628), ISSN 0141-0229... 

The xylan degradation rates relative to those of mannan ranged from 0.3 to 0.4 at the end of the experiment (80 hr). The same values were obtained before the additional action of mannanase on the samples treated with one of the three cellulases for 48 hr (Table III, Column 14). The corresponding values relative to the cellulose degradation rates ranged from 0.5 to 0.7 for the samples treated with cellulase only (48 hr) and after combined cellulase-mannase action (Table III, Column 15). 

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... 

Comparison of Cellulose/Hemicellulose, Glucan/Xylan, and Xylan Degradation/Glucan Degradation Ratios for Preliminary Tests (4) at 0.77 g of HzO/g of Dry Stems ... 

Higher conversions of xylan and glucan were seen with increases in both moisture content and inoculum size (Table 4), but no correlation was observed between the conversions and the relative amounts of inoculum and moisture (ratio of inoculum to moisture content not shown). Thus, it is unlikely that these two parameters comprise an interaction effect that is important to the operation of the system. Lower moisture contents gave lower overall amounts of degradation, but seemingly better selectivities for xylan degradation although coefficients of variation for conversions were... 

Christov, L. P., and Prior, B. A., Esterases of xylan-degrading microorganisms Production, properties, and significance. Enzyme Microb Technol 1993, 15 (6), 460-75. 

Castanares, A., Hay, A. J., Gordon, A. H., McCrae, S. I., and Wood, T. M., D-xylan-degrading enzyme system from the fungus Phanerochaete chrysosporium isolation and partial characterisation of an alpha-(4-0-methyl)-D-glucuronidase. J Biotechnol 1995, 43 (3), 183-94. 

Because of the heterogeneity of xylan, its hydrolysis requires the action of a xylanolytic enzyme system which is composed of P-l,4-endoxylanase (E.C. 3.2.1.8), P-xylosidase (E.C. 3.2.1.37), a-L-arabinofuranosidase (E.C. 3.2.1.55), a-glucuroni-dase (E.C. 3.2.1.-) and acetyl xylan esterase (E.C. 3.1.1.6) activities (Table 11.4-3). The concerted action of these enzymes converts xylan to its constituent sugars (Fig. 11.4-6). Xylan-degrading enzymes have been reported to be present in marine and... 

Plant polysaccharides are a major source of renewable substrates for the chemical, pharmaceutical and feed industries[1291. Xylan-degrading enzymes have considera-... 

Table 2 The effect of various carbon sources on production of xylan-degrading enzymes by different H. jecorina (T. reesei) strains. ...

Xylan-degrading enzymes, especially xylanases, have considerable potential in several biotechnological applications. In some processes, the use of purified enzymes is required. However, in other applications, the presence of additional enzyme activities is desired. Commercial applications suggested for xylanases involve the conversion of xylan, which is present in wastes from the agricultural and food industry, into xylose (2). Similarly, xylanases could be used for the clarification of juices, for the extraction of coffee, plant oils and starch and for the production of fuel and chemical feedstocks (3). 

The preparation of 4-thioxylobiose, which was used as a non-metabolized inducer of xylan-degrading enzymes, was based on reaction of 1-thio-D-xylose with l,2,3-tri-0 -benzoyl-6-L-arablno-pyranose i -triflate. 

Tuncer M., Ball A.S., Co-operative actions and degradation analysis of purified xylan-degrading enzymes from Thermomonosporafusca BD25 on oat-spelt xylan, J. Appl. Microbiol., 94(6), 2003,1030-1036. 

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