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This paper deals with the characterization of extracellular thermostable xylanase produced by Chaetomium globosum, an ascomycete fungus. The crude extracellular enzyme was found to have temperature and pH optima of 60°C and 5.0 respectively. The enzyme hydrolyses xylan to a mixture of xylo-oligomers. Xylobiose and xylose are the major breakdown products.

Localisation of endo p-1 -4-xylan xylanohydrolase and p-xylosidase was studied in Chaetomium globosum when the fungus was grown on 1 % (w/v) birchwood xylan. Although both enzymes are present in the soluble fraction of the cell, xylanase activity was membrane bound whereas B-xylosidase activity was associated with the cell wall. Xylanase andp-xylosidase acted synergistically on the xylan backbone with the appearance of xylo-oligosaccharides, xylobiose and xylose.Chuetomium globosum is an ascomycete fungus that is capable of utilizing both untreated cellulosic and lignocellulosic substrates as the sole source of carbon. This suggests that the fungus secretes both cellulases and hemicellulases. These enzymes play an important role in both fungal nutrition and the invasion of higher plant tissues containing lignocellulose.