Xylanolytic activity

T ine structural studies on woody cell walls attacked by ectoenzymes of fungi in situ are numerous (cf. 1,2). In contrast, investigations on the selective degradation of cell walls by enzymes isolated from fungi are few. Jutte and Wardrop (3) attempted the use of crude commercial cellu-lase preparations to determine the degradation pattern of Valonia cellulose and beechwood fibers. Similar use of commercial preparations of enzymes was made by Reis and Roland (4) to evaluate the nature of diverse cell walls and to show the distribution of polysaccharides. An endo-/ -l,4-xylanase with specific xylanolytic activities was isolated from a commercial cellulase preparation using chromatographic methods and... 

Fig. 1. Cellulolytic and xylanolytic activities and extracellular protein during time course of the cultivation of P. brasilianum IBT 20888. (A) Cellulolytic activities on cellulose (B) cellulolytic activities on xylan (C) xylanase activities on cellulose and (D) xylanolytic activities on xylan. ( ) BG ( ) CBH ( T ) EG ( O ) BX ( O ) AF ( V ) EX (+) extracellular protein ( —) cultivation on cellulose and (----) cultivation on xylan.

Studies of 12 different Penicillium species have demonstrated that there was a coinduction between cellulolytic and xylanolytic activities whether the substrate was cellulose or xylan, whereas activities of cellulolytic enzymes were generally higher during growth on cellulose than on xylan [28]. The conclusion was further confirmed by our studies of P. decumbens (data not shown). Together with the above results of starch and protein experiments, it must be the high levels of water soluble cello-oligosaccharides... 

All the strains were found to utilize cellulose and produce extracellular cellulase and xylanase enzymes. F. oxysporum 841 was found to be a potential mould for direct conversion of cellulose to ethanol/acetic acid. Though other species, e.g. F. oxysporum 2018, 62287 and 62291 also produced comparable amounts of cellulase and xylanase enzymes, only traces of ethanol and acetic acid were detected in non-aerated cultures. Maximiun cellulase activity was observed after 96 h of bioconversion process. F. oxysporum VTT-D-80134, however, was not found to produce sufficient cellulolytic and xylanolytic activities to convert cellulose or hemicellulose directly into ethanol [81]. 

Lee SF, Forsberg CW, Gibbins LN (1985) Xylanolytic activity of Clostridium acetobuiyticum. Appl Environ Microbiol 50 1068—1076 Lee SF, Forsberg CW, ttrayJB (1987a) Purification and characterization of two endoxylanases from Clostridium acetobutylicum. ATCC 824. Appl Environ Microbiol 53 644—650... 

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. 

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. 

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 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. 

Of potential interest are also the cellulolytic, xylanolytic and pollulan-hydrolyzing activities detected in Thermophilum strains and in AN 1, a member of the Thermococcales [59]. An additional candidate for biotechnical application is also represented by the a-glucosidase from P. furiosus, which exhibits the highest thermostability (to.5(98°C) = 46-48 h) and temperature optimum for activity (105-115 C) compared to all enzymes investigated so far [60] (Table 1). 

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... 

N.N.M.E. van Peij, J. Brinkmann, M. Vrsanska, J. Visser and L.Hi de Graaff, 5-Xylosidase activity, encoded by xlnD, is essential for complete hydrolysis of xylan by Aspergillus niger but not for induction of the xylanolytic enzyme spectrum. Eur. J. Biochem., 1997, 245, 164-173. 

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