| Summary: | 碩士 === 國立屏東科技大學 === 生物科技研究所 === 94 === Xylan, the major component of the hemicellulose complex, is a heterogeneous polysaccharide, formed byβ-D-xylopyranosyl residues linked through β-1,4- glycosidic bonds. In general, depolymerization of xylan is accomplished by the action of β-D-xylanase (EC 3.2.1.8). Beta-D-xylanase hydrolyze β-1,4- glycosidic linkages of the xylan backbone to produce short chain xylooligo- saccharides of various lengths. Xylanase products have been applied in papermaking, food, feed and others. In present study, the xylanase was secreted by S. thermonitrificans NTU-88 after xylan induction, and the enzyme was further purified and characterized. The crude xylanase possessed optimal pH and temperature at pH7.0 and 70℃, respectively. The products of xylan hydrolyzed by unpurified enzyme were xylose, xylobiose and xylotriose. The crude enzyme was further purified by hydrophobic interaction chromatography, ion exchange chromatography and gel filtration chromatography and two separated fraction, xylanaseⅠ and xylanaseⅡ, with xylanase activity were obtained. The Mw and pI of two fractions were 28KDa, 5.2 and 25KDa, 5.5, respectively. The purified enzymes demonstrated optimal pH and temperature at pH6.5, 70℃ and pH5.0, 70℃, respectively. These two enzymes belonged to endo xylanase was also confirmed by hydrolysis products. The xylanaseⅠ was further identified by LC/MS/MS, and the amino acid sequences of xylanaseⅠwere similar to those of GH10.
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