Abstract: Endoxylanases from Trichoderma viride were separated from each other by selective adsorption with insoluble oat xylan. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), both xylanases reached electrophoretically pure. The molecular weights of the bounded (XynⅡ) and the unbounded (XynⅠ) components were 26.5 and 29.5ku respectively, and their K_m s toward birch xylan were 1.73 and 3.16g/L, respectively. The hydrolysates from oat xylan using XynⅠ,XynⅡ and their mixture for hydrolysis were analysed by HPLC. It was showed that Xyn Ⅰ hydrolyzed mainly the unsubstituted regions of oat xylan, and hydrolytes were high xylooligosaccharides; whereas XynⅡexhibited greater catalytic versatility than XynⅠand were able to attack substituted regions of the polysaccharide and showed greater activity to low xylooligosaccharides than XynⅠ to give xylobiose as the main hydrolysate. The purified xylanases were acidic enzymes. XynⅡ was sensitive to pH value, and XynⅠ was stable in the wide range of pH values. The optimal reaction temperatures of XynⅠ and XynⅡ were 45 and 55℃ respectively, and their optimal pH values were 4.5 and 5.5 respectively.

Key words: oat xylan, endoxylanases