Thermoascus aurantiacus showed the best growth on medium containing pectin as a carbon source. The enzyme involved in the production of catalase in the fungus was alcohol oxidase. Formaldehyde dehydrogenase and formate dehydrogenase, in addition to alcohol oxidase and catalase, were detected in the cells grown on pectin. Alcohol oxidase was alkali resistant (pH 7 to 11), and was comparatively heat stable (55° C).