Thermostable xylanase from Talaromyces byssochlamydoides YH-50 was fractionated into three components, tentatively named X-a, X-b-I and X-b-II during the purification steps. X-a, X-b-I and X-b-II were further purified by consecutive column chromatographies until found to be in homogeneous states on disc electrophoresis. X-a, X-b-I and X-b-II contained 36.6%, 31.5% and 14.2% carbohydrate residues, respectively. The carbohydrate residues were glucose, mannose and fucose. X-a, X-b-I and X-b-II were optimally active at 70~75°C and pH 4.5~5.5. X-a, X-b-I and X-b-II retained 65, 54 and 30%, respectively, of the original activity after heating at 95°C for 5 min. The activities of X-a, X-b-I and X-b-II were considerably inhibited by HgCl2 and KMnO4. The hydrolysis products from xylan with X-a were xylose, arabinose, glucose, xylobiose and other xylooligosaccharides, whereas the hydrolysis products from xylan with X-b-I and X-b-II were xylose and xylobiose.

A fungus identified as Fusarium equiseti was isolated from soil and found to carry out 7,3-hydroxylation of lithocholic acid to ursodeoxycholic acid (35% yield; 350 mg/liter) in 112 h.

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Strain YH-50 from a thermophilic fungus isolated from compost heaps produced the highest amount of thermostable xylanase among 1 80 isolates tested. This xylanase-producing strain YH-50 was identified as Talaromyces byssochlamydoides Stolk & Samson by taxonomical characteristics. Whenit was cultivated in solid wheat bran mediumcontaining xylan as an additive carbon source, the maximalamount of thermostable xylanase was produced after 3 days at 50°C. This culture filtrate hydrolyzed 90%ofxylan as xylose, and the sugars formed were xylose, arabinose, glucose and galactose. The optimal pH and temperature were 5.5 and 70°C, respectively. The enzyme was quite stable after heating at 65°C for 5 min and retained 55% of original activity after heating at 95°C for 5 min. Wehave been considered that thermophilic fungi are useful for the production of industrial enzyme because of the rapid growth and prevention of comtamination. Enzymes responsible for the decomposition of plant materials, i.e., xellulase,1* /?-glucosidase,2)3)

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