Showing papers on "Xylanase published in 1975"

Regulation of synthesis of cell wall degrading enzymes by Veticillium albo-atrum and Fusarium oxysporum f. sp. lycopersici☆

Abstract: Induction and catabolite repression of synthesis of cell wall degrading enzymes by the vascular wilt fungi Verticillium albo-atrum and Fusarium oxysporum f. sp. lycopersici have been studied. In cultures containing inorganic salts and tomato stem cell walls each fungus produced a range of extracellular, polysaccharide degrading enzymes. In V. albo-atrum cultures, the enzymes appeared sequentially over 2 to 9 days in the order endopolygalacturonase (endo-PG), exo-arabinanase, endo-pectin-trans-eliminase (endo-PTE), endoxylanase and cellulase; β- d -galactosidase, galactanase and β- d -glucosidase were also produced. Under similar conditions F. oxysporum produced endo-PG, endo-PTE, arabinanase, β- d -galactosidase, xylanase and cellulase. Synthesis of each enzyme was almost always induced specifically by the sugar or uronic acid unit predominant in the specific polymeric substrate for the enzyme. This became evident only when inducers were supplied at rates which prevented their accumulation in cultures. Exceptionally, cellulase was induced by cellobiose but not glucose, and β-galactosidase a and galactanase were induced both by d -galactose and the structurally related l -arabinase. Synthesis was repressed when inducers were present in slight excess of requirements for growth. Synthesis by V. albo-atrum of endo-PG and endo-PTE increased with inducer supply until inducer began to accumulate, then decreased sharply and was almost completely repressed at supply rates three times the optimal value. Synthesis of exo-arabinanase and β-galactosidase decreased as supply of arabinose increased above the optimum but remained at much higher levels relative to those for endo-PG and endo-PTE. Constitutive synthesis of enzymes by V. albo-atrum was also catabolite repressed but to a lesser degree. The significance of induction and catabolite repression in pathogenesis in vascular wilts is discussed.

On the Modes of Action of Three Xylanases Produced by a Strain of Aspergillus niger van Tieghem

Abstract: The modes of action of three xylanases (I, II and III) produced by Aspergillus niger van Tieghem on several substrates were investigated. Xylanase I possesed the strongest activity against xylooligosaccharides among the three enzymes and converted them into xylose and xylobiose. Xylanase II and III catalyzed a glycosylating reaction and produced higher polymerized xylooligosaccharides from xylotetraose or xylopentaose. Among three enzymes, xylanase II could split α1,3-arabinofuranosidic bond of arabinose-xylose mixed oligosaccharides.In the case of hydrolysis by three xylanases on xylan and arabinoxylan, the maximum hydrolysis degree and the reaction products were compared with each other. From the results, some speculation were made concerning the modes of action of the enzymes.

Studies on xylanase fromBasidiomycetes

Abstract: Formation of extracellular xylanase was studied in 10 strains of wood-destroying fungi belonging toBasidiomycetes during their submerged cultivation with willow sawdust. The highest enzyme activity was found in the fungusTrametes hirsuta (Wulf.) Pilat. The effect of sources of carbon and nitrogen, cultivation time and initial pH of the cultivation solution on the formation of xylanase by the fungusTrametes hirsuta was investigated. The highest production of the enzyme was reached during cultivation in the presence of willow sawdust, asparagine and at the initial pH of 5.0. The presence of xylanase, cellulase, mannanase and amylase as well as of beta-xylosidase, beta-glucosidase, beta-mannosidase and betagalactosidase was demonstrated in the enzyme preparation obtained after a 10-day submerged cultivation ofTrametes hirsuta under optimal conditions.

A New Method for Preparation of Xylobiose, Eliminating Xylose from Enzymatic Xylan Hydrolyzate by Yeast

Abstract: Establishment of a new method for preparation of xylobiose was investigated.When hardwood xylan was hydrolyzed by the xylanase system of Streptomyces sp. E–86, the hydrolyzate mainly consisted of xylose and xylobiose in an approximate ratio of 1: 1.Yeast strains selected in this paper, effectively and selectively metabolized all of xylose without any degradation of xylobiose.By successive treatments of xylan with Streptomyces xylanase system and xylose-metabolizable yeast, 70.4 g of crystalline xylobiose was obtained from 172 g of xylan.