Xylan degrading enzymes

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... 

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. 

C15H26O13 414.363 Formed by a xylan degrading enzyme from the cells of Cryptococcus albidus. Syrup. Md -37.2 (c, 1.4 in H2O). 

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... 

Trichoderma (9-10). Much less is known about the concurrent production of the enzymes which cleave substituent groups of the xylan polymer. The presence of acetyl xylan esterases (11,12) and a-glucuronidases (13-15) in xylanolytic enzyme systems has only recently been pointed out. Although a-arabinosidases have mainly been studied as arabinan-degrading enzymes (16), they have also been shown to release arabinose from xylans (17). 

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... 

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

P-Xylosidases are being used commonly in paper industry for complete degradation of xylans. The enzymes used in the synthesis of xylose-containing compounds have also been reported. For example, Eneyskaya et al. (50) have used />-nitrophenyl P-D-xylopyranosides (XyiPpNP) as a donor and a 3-xylosidase ixom Aspergillus sp. in the synthesis of several 31,4-D-xylooli-gosaccharides as P-xylanase substrates. 

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