Purification and properties of thermostable xylanases from mesophilic fungus strain Y-94.

Abstract

A mesophilic fungal strain Y-94 produced three types of thermostable endo-xylanases accompanied by the formation of a large amount of cellulase. These xylanases were separated from the cellulase by heat treatment at 65°C for 2.5 hr and purified by DEAE-Toyopearl chromatog-raphy, chromatography on an anion exchanger (PBE 94), and Bio-Gel A 0.5 m gel filtration. The molecular weights of the three types of xylanase, designated as xylanase A, B and C, were 51,000, 48,000, and 35,000, respectively. All three enzymes showed highest activity at pH 4.9 and 80°C in lOmin of incubation, and had the same hydrolysis pattern of larch wood xylan with the end- products of xylobiose and xylose. Thus their activities appear essentially the same but not their stabilities. Xylanase A and B were stable from pH 2.5 to 9.0 but xylanase C was unstable above pH 5.5. Xylanase C was unstable at 70°C where other two were stable.