Purification and characterization of two xylanases from Chaetomium thermophile var. coprophile

Abstract

Two xylanases (I and II) out of several extracellular xylanases produced by the thermophilic fungus Chaetomium thermophile var. coprophile were purified to homogeneity by a combination of ion exchange and gel filtration chromatographic procedures. They had molecular weights of 26 000 (xylanase I) and 7000 (xylanase II). The temperature optima for xylanase I and II were 70 and 60 °C, and they were optimally active at pH 4.8–6.4 and 5.4–6.0, respectively. Xylanase I was found to be comparatively more stable than xylanase II at higher temperatures. Amino acid composition indicated that xylanase I contained high amounts of glycine, threonine, and low amounts of histidine and sulphur-containing amino acids. Each enzyme released different hydrolysis products from larch wood xylan. Xylanase I produced mainly xylobiose and xylotriose whereas xylanase II produced mainly xylobiose.Key words: Xylanase, enzyme purification, characterization, Chaetomium thermophile.