Abstract

The thermophilic fungus Thermoascus aurantiacus 179-5 produced large quantities of a glucosidase which preferentially hydrolyzed maltose over starch. Enzyme production was high in submerged fermentation, with a maximal activity of 30 U/ml after 336 h of fermentation. In solid-state fermentation, the activity of the enzyme was 22 U/ml at 144 h in medium containing wheat bran and 5.8 U/ml at 48 h when cassava pulp was used as the culture medium. The enzyme was specific for maltose, very slowly hydrolyzed starch, dextrins (2-7G) and the synthetic substrate (α-PNPG), and did not hydrolyze sucrose. These properties suggest that the enzyme is a type II α-glucosidase. The optimum temperature of the enzyme was 70?. In addition, the enzyme was highly thermostable (100% stability for 10 h at 60? and a half-life of 15 min at 80?), and stable within a wide pH range.

• Keywords: glucosidase; Thermoascus; submerged fermentation; solid-state fermentation; thermophilic; thermostable