Saccharification of xylan by an amyloglucosidase of Termitomyces clypeatus and synergism in the presence of xylanase (original) (raw)
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Biotechnology Progress, 1995
An amyloglucosidase was purified to homogeneity from the culture filtrate of Termitomyces clypeatus, using the following steps: ammonium sulfate fractionation, DEAE-Sephadex chromatography, and HP-GPLC on a n Ultropac TSK-G3000 SWG column. The enzyme was a glycoprotein with a minimum molecular weight of 56 000. It had appreciable activity on glycogen and amylopectin, moderate activity on maltose, and little activity on panose. The enzyme, unlike fungal amyloglucosidase (Aspergillus niger), could liberate glucose from xylans. The enzyme had K, = 1.81 mg/mL and V, = 82.1 pmoVmidmg for starch hydrolysis and K , = 4.36 mg/mL and V, = 57.7 pmoV midmg for the hydrolysis of larch wood xylan. Among the different inhibitors, NBS and CDTA were the most potent. Previously the enzyme was shown [Khowala, S .; et al. Appl. Microbiol. Technol. 1992,37,287-2921 to have synergistic activity on xylan hydrolysis similar to other xylanolytic enzymes: a-arabinofuranosidase or a-glucuronidase. Since the amyloglucosidase was not active on cellulose, arabinogalactan, or P-glucans, which may be present as contaminants in xylan, the probable liberation of glucose directly from xylan by the enzyme was indicated.
Microbiology, 1985
The mushroom Termitomyces clypeatus produces a single endoxylanase (1,4-P-~-xylan xylanohydrolase, EC 3.2.1 .8) in the presence of either dextrin or xylan as sole source of carbon. The enzymes produced in the two conditions are different. The enzyme induced by xylan has been purified 67-fold from the culture filtrate of T. clypeatus. The enzyme preparation gave a single protein band on SDS-PAGE, corresponding to a molecular weight of about 24000. The enzyme has an isoelectric point at pH4-0 and acts on arabinoxylan and arabinogalactan, but not amylopectin or galactomannan. It shows maximum activity on xylan (I ,4-P-linked Dxylopyranose units) at pH 3.5 and 55 OC and is fairly stable up to 60 OC. The K , for xylan is 4 mg ml-l. Hg2+, Fe2+ and Ag+ are the most potent inhibitors of the enzyme. The pH optimum and molecular weight of this inducible xylanase differ from those of the enzyme produced by the same organism grown in dextrin medium.
Enzyme and Microbial Technology, 1988
The mushroom Termitomyces clypeatus produces two endoxylanases (D) and (X) when grown in media containing dextrin and xylan as carbon sources, respectively. Endoxylanase (D) showed wide variation in its activity on different lots of xylan preparations, and its activity was found to be dependent upon the composition of xylans. The xylose-liberating endoxylanase (X) did not discriminate between different xylans. The activity of xylanase (D) was found to decrease as the proportion of xylose in different xylan preparations increased. The dialyzable oligosaccharides from the digestion of xylan by enzyme (D) contained constituent sugars of xylan, whereas xylose was the main constituent sugar of the undialyzable fraction. Enzyme (D) also could not liberate any reducing group from carboxymethyl xylan (CMX), a suitable substrate for viscometric and colorimetric assays of endolytic activity of xylanases. CMX was found to be modified preferentially at the substituent sugars of xylan rather than at backbone residues. Thus CMX proved to be a specific substrate for colorimetric assay of true endoxylanase activity.
Xylanases from fungi: properties and industrial applications
Applied Microbiology and Biotechnology, 2005
Xylan is the principal type of hemicellulose. It is a linear polymer of β-D-xylopyranosyl units linked by (1-4) glycosidic bonds. In nature, the polysaccharide backbone may be added to 4-O-methyl-α-D-glucuronopyranosyl units, acetyl groups, α-L-arabinofuranosyl, etc., in variable proportions. An enzymatic complex is responsible for the hydrolysis of xylan, but the main enzymes involved are endo-1,4-β-xylanase and β-xylosidase. These enzymes are produced by fungi, bacteria, yeast, marine algae, protozoans, snails, crustaceans, insect, seeds, etc., but the principal commercial source is filamentous fungi. Recently, there has been much industrial interest in xylan and its hydrolytic enzymatic complex, as a supplement in animal feed, for the manufacture of bread, food and drinks, textiles, bleaching of cellulose pulp, ethanol and xylitol production. This review describes some properties of xylan and its metabolism, as well as the biochemical properties of xylanases and their commercial applications.
Bioprocess and Biosystems Engineering, 2012
Agroindustrial residues are materials often rich in cellulose and hemicellulose. The use of these substrates for the microbial production of enzymes of industrial interest is mainly due to their high availability associated with their low cost. In this work, corncob (CCs) particles decomposed to soluble compounds (liquor) were incorporated in the microbial growth medium through autohydrolysis, as a strategy to increase and undervalue xylanase and b-xylosidase production by Aspergillus terricola and Aspergillus ochraceus. The CCs autohydrolysis liquor produced at 200°C for 5, 15, 30 or 50 min was used as the sole carbon source or associated with untreated CC. The best condition for enzyme synthesis was observed with CCs submitted to 30 min of autohydrolysis. The enzymatic production with untreated CCs plus CC liquor was higher than with birchwood xylan for both microorganisms. A. terricola produced 750 total U of xylanase (144 h cultivation) and 30 total U of b-xylosidase (96-168 h) with 0.75% untreated CCs and 6% CCs liquor, against 650 total U of xylanase and 2 total U of b-xylosidase in xylan; A. ochraceus produced 605 total U of xylanase and 56 total U of b-xylosidase (168 h cultivation) with 1% untreated CCs and 10% CCs liquor against 400 total U of xylanase and 38 total U of b-xylosidase in xylan. These results indicate that the treatment of agroindustrial wastes through autohydrolysis can be a viable strategy in the production of high levels of xylanolytic enzymes.
International Biodeterioration & Biodegradation, 2009
Hemicellulose consists of non-cellulosic polysaccharides, with xylans and mannans as their main examples. In nature, xylan can be first degraded to xylooligosaccharides and finally to xylose by certain microorganisms. White-rot fungi basidiomycetes Pleurotus sp. BCCB068 and Pleurotus tailandia were used to degrade oat-spelts xylan under submerged fermentation for a period of 40 days. The study obtained activities of endo-1,4-β-xylanase and β-xylosidase and determination of xylan products by degradation. The fungi reached significant levels of xylan degradation by Pleurotus sp. BCCB068 (75.1%) and P. tailandia (73.4%), following formations of xylooligosaccharides and sugar monomers. These Pleurotus strains proved to be a feasible alternative for biotechnological processes related to degradation of hemicellulose sources.
Production of fungal xylanases
Bioresource Technology, 1996
Applications of xylanases can be found in the food, feed and pulp~paper industry. Filamentous fungi are particularly interesting producers of this enzyme from an industrial point of view, due to the fact that they excrete xylanases into the medium. Furthermore, xylanase levels from fungal cultures are generally much higher than those from yeasts or bacteria. In addition to xylanase, fungi typically produce several accessory xylanolytic enzymes, which are necessary for debranching substituted xylans. An important factor for efficient xylanase production is the choice of an appropriate inducing substrate, either insoluble or soluble, as well as optimization of the medium composition. In addition, the substrate can influence the concomitant formation of cellulolytic enzymes in certain organisms. Bioprocess parameters, that can affect activities and productivities of xylanase attained in a fermentation process, as well as the concurrent formation of cellulases, include the pH, temperature, or agitation. Xylanase activities produced by different organisms, including filamentous fungi and yeasts, are compared for both submerged and solid-state fermentations. When available, data on the concurrent formation of cellulolytic enzyme activities are included. On an industrial scale, xylanases are produced mainly by Aspergillus and Trichoderma spp. A list of commercially available xylanases and their potential applications is given.
Xylan is the principal type of hemicellulose. It is a linear polymer of β-D-xylopyranosyl units linked by (1-4) glycosidic bonds. In nature, the polysaccharide backbone may be added to 4-O-methyl-α-D-glucuronopyranosyl units, acetyl groups, α-L-arabinofuranosyl, etc., in variable proportions. An enzymatic complex is responsible for the hydrolysis of xylan, but the main enzymes involved are endo-1,4-β-xylanase and β-xylosidase. These enzymes are produced by fungi, bacteria, yeast, marine algae, protozoans, snails, crustaceans, insect, seeds, etc., but the principal commercial source is filamentous fungi. Recently, there has been much industrial interest in xylan and its hydrolytic enzymatic complex, as a supplement in animal feed, for the manufacture of bread, food and drinks, textiles, bleaching of cellulose pulp, ethanol and xylitol production. This review describes some properties of xylan and its metabolism, as well as the biochemical properties of xylanases and their commercial applications.