Xylanolytic enzyme

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... 

Xylanolytic enzymes free of cellulases can be applied in the pulp and paper, textile, and food industries and in basic research. However, most microorganisms grown under natural conditions produce both xylanases and cellulases. Strategies to produce xylanolytic systems free of cellulases are elimination of cellulase activity by separation or inhibition, selection and construction of cellulase-negative strains, and finding conditions for separate production of xylanolytic systems by cellulolytic strains. 

Pure xylanases can be useful in l ic research. They fmd application in analytical procedures designed to quantify specific xylan constituents 10) and to study xylan structure. They can be used to preparation of defined xylooligosacchaiides, eidia by hydrolysis of xylan 11-14) x by transglycosylation at high substrate concentrations 15,16). These products may serve as assay substrates and model compounds to study the mechanism of action of xylanolytic enzymes. Finally, xylanolytic eiuymes play an imptutant role in complex enzyme preparations used to the release of plant protoplasts. 

No doubt the cost of xylanolytic enzymes will be one of the factors determining their application in the pulp and paper industry as well as in other areas. Economically feasible xylanase production can be achieved in paper mills employing xylanase-positive transformants of common industrially used microorganisms that are capable of utilizing inexpensive carbon sources originating there. A substantial improvement in the production of xylanolytic systems can be expeaed from mutants of non-cellulolytic microorganisms that are resistant to catabolic repression. Such mutants usually exhibit hyperproduction of extracellular enzymes. 

Finally, attention should also be devoted to the elaboration of simple and reliable assays of xylanolytic enzymes that provide information on their efficiency in the application process. 

The xylanolytic enzyme system of Trichoderma reesei, a well-known producer of cellulolytic enzymes, is versatile and well suited for the total hydrolysis of different xylans. It consists of two major, specific and several non-specific xylanases, at least one / -xylosidase, a-arabinosidase and a-glucuronidase and at least two acetyl esterases. The hydrolysis of polymeric xylans starts by the action of endoxylanases. The side-groupcleaving enzymes have their highest activities towards soluble, short xylo-oligosaccharides, and make the substituted oligosaccharides again accessible for xylanases and / -xylosidase. 

Xylan is an essential constituent of hardwoods, softwoods, and annual plants. In enzymatic processing of lignocellulosic biomass, xylanolytic enzymes may be used either individually, in selected mixtures for specific effects on only the xylan component of the raw material, or in mixtures with cellulolytic, pectinolytic or amylolytic enzymes. 

POUTANEN puls Trichoderma Xylanolytic Enzyme System... 

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). 

Enzyme Purification. The purification of the xylanolytic enzymes began with adsorption on a cation exchanger (CM-Sepharose FF) at pH 4.0. The final purification was accomplished by another ion exchange step as described previously for xylanase (24), / -xylosidase (25), a-arabinosidase (26) and acetyl esterase (27). 

Table I. Xylanolytic Enzymes Isolated from Trichoderma reesei...

Synergism between the different xylanolytic enzymes was further demonstrated when a partially purified enzyme preparation was used as a source of xylanase activity (Table IV). This preparation, separated from... 

The xylanolytic enzyme system of T. reesei consists of several endoxy-lanases, at least three different exoglycosidases and at least two acetyl esterases. These enzymes contribute to the hydrolysis of plant cell walls in many of the applications of cellulolytic T. reesei enzyme preparations. A schematic figure of the suggested hydrolysis mechanism of xylans by the... 

Two broad areas of application for xylanolytic enzymes have been identified (1). The first involves the use of xylanases with other hydrolytic enzymes in the bioconversion of wastes such as those from the forest and agricultural industries, and in the clarification and liquification of juices, vegetables and fruits. For these purposes, the enzyme preparations need only to be filtered and concentrated as essentially no further purification is required. Several specific examples of applications involving crude xylanase preparations include bioconversion of cellulosic materials for subsequent fermentation (2) hydrolysis of pulp waste liquors and wood extractives to monomeric sugars for subsequent production of single cell protein (3-5). Xylose produced by the action of xylanases can be used for subsequent production of higher value compounds such as ethanol (6), xylulose (7) and xyIonic acid (8-9). 

Screening Genus Penicillium for Producers of Cellulolytic and Xylanolytic Enzymes... 

The highest EX and AF activities were measured after cultivation of T. reesei Rut C30 on xylan, (59 and 0.42 U/mL, respectively) (Table 3). These activities were with a few exceptions almost twice as high as any of the activities obtained after cultivation of the Penicillium species. BX activity reached by far the highest activity after cultivation of T. reesei Rut C30 on cellulose. This was not the case for the Penicillium species that had the highest BX activity when they were cultivated on xylan. XA activity could not, like FPA, be fully explained by the individual xylanolytic enzymes, as demonstrated in a comparison of T. reesei Rut C30 and P. simplicissimum IBT 15303 after growth on cellulose. 

The filamentous fungi investigated showed coinduction of cellulolytic and xylanolytic enzymes. During growth on cellulose, products from the hydrolysis of cellulose also induced production of xylanolytic enzymes, and during growth on xylan, products from the hydrolysis of xylan also induced the production of cellulolytic enzymes. 

Teunissen MJ, Smits AA, Op den Camp HJ, Huis in t Veld JH, Vogels GD (1991) Fermentation of cellulose and production of cellulolytic and xylanolytic enzymes by anaerobic fungi from ruminant and non-ruminant herbivores. Arch Microbiol 156 290-296 Tielens AG, Rotte C, van Hellemond JJ, Martin W (2002) Mitochondria as we don t know them. Trends Biochem Sci 27 564-572... 

Bailey, M. J. and Poutanen, K., Production of xylanolytic enzymes by strains of Aspergillus. Appl Microbiol Biotechnol 1989, 30 (1), 5-10. 

Dry citrus peels are rich in pectin, cellulose, and hemicellulose and may be used as a fermentation substrate. Production of multienzyme preparations containing pectinolytic, cellulolytic, and xylanolytic enzymes by the mesophilic fungi A. niger BTL, Fusarium oxysporum F3, Neurospora crassa DSM 1129, and Penicillium decumbens under SSF on dry orange peels was enhanced by optimization of initial pFI of the culture medium and initial moisture level (Mamma et al., 2008). Under optimal conditions A. niger... 

Baeck, Busch, Verschuere, Katrien Procter Gamble Cleaning compositions comprising xylanolytic enzymes Compositions have xylanase activity show an excellent boost in cleaning performance on fruit, vegetables, and mud or clay soils... 

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... 

Figure 11.4-6. (A) Action of xylanolytic enzymes on an hypothetical xylan structure. (B) Action of...

Lindner, C., Stulke, J., Hecker, M. (1994). Regulation of xylanolytic enzymes in Bacillus subtilis. Microbiology, 140, 753-757. 

Selig M, Adney W, Himmel M, Decker S. (2009). The impact of cell wall acetylation on corn stover hydrolysis by cellulolytic and xylanolytic enzymes. Cellulose, 16(4), 711-722. 

---