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 chromatography, chromatography on an anion exchanger (PBE 94), and Bio-Gel A 0.5m 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 10min of incubation, and had the same hydrolysis pattern of larch wood xylan with the endproducts 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.