title: Screening of fungal beta-xylanases for production of acidic xylooligosaccharides using in situ reduced 4-O-methylglucuronoxylan as substrate.
abstract: Fungal beta xylanases were screened for production of acidic xylooligomers from 4-O-methylglucuronoxylan. In situ reduced hardwood xylan was used as substrate because the products of neutral- and acidic-branched xylooligomers help define substrate specificity of the enzymes. Borohydride reduction in situ transformed 30% of 4-O-methyl-alpha-D-glucopyranosyluronic acid residues into 4-O-methyl-alpha-D-glucopyranosyl residues and reduced C-1 end groups in the xylan backbones. A total of ten beta-xylanase fractions from four fungi were partially purified by chromatography by anion exchange and molecular sieving, and graded qualitatively for enzymatic hydrolysis of the substrate. The yield of acidic xylooligomers was highly affected by whether alpha-glucuronidases were present in the beta-xylanase fractions. Some fractions gave free 4-O-methyl-alpha-D-glucopyranosyluronic acid, but none of the enzyme fractions could release free 4-O-methyl-alpha-D-glucose. Among the beta-xylanase fractions studied, xylanase II of Trichoderma viride was the best producer of aldotetraouronic acid [2-O-(4-O-methyl-alpha-D-glucopyranosyluronic acid)-D-xylotriose]. The results obtained suggested that there was a difference in the steric hindrance of the branch point on fungal beta-xylanases between 4-O-methyl-alpha-D-glucopyranosyl and 4-O-alpha-D-glucopyranosyluronic acid residues.
authors.affiliation: Forestry and Forest Products Research Institute, Tsukuba Norin Kenkyu Danchi-nai, Ibaraki, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ishihara
authors.forename: M
authors.initials: M
authors.lastname: Nojiri
authors.forename: N
authors.initials: N
authors.lastname: Hayashi
authors.forename: T
authors.initials: T
authors.lastname: Nishimura
authors.forename: K
authors.initials: K
authors.lastname: Shimizu
mesh_terms: D001487:Basidiomycota / Q000201:enzymology; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D005658:Fungi / Q000201:enzymology*; D006868:Hydrolysis; D006999:Hypocreales / Q000201:enzymology; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors; D014197:Trees; D014242:Trichoderma / Q000201:enzymology; D043325:Xylan Endo-1,3-beta-Xylosidase; D014990:Xylans / Q000737:chemistry / Q000378:metabolism*; D014995:Xylosidases / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D009844:Oligosaccharides; D014990:Xylans; D014995:Xylosidases; D043325:Xylan Endo-1,3-beta-Xylosidase