A HIGHLY THERMOSTABLE BETA-GLUCOSIDASE ACTIVITY FROM THE THERMOPHILICFUNGUS HUMICOLA-GRISEA VAR THERMOIDEA - PURIFICATION AND BIOCHEMICAL-CHARACTERIZATION

Humicola grisea var. thermoidea grown in sugar cane bagasse produced a nd secreted two major protein components exhibiting beta-D-glycosidase activities (forms I and II). Form I was purified to apparent homogene ity (PAGE and SDS-PAGE) by a three-step procedure involving acetone pr ecipitation, DEAE-cellulose chromatography and filtration in Bio-Gel P -100. The purified enzyme was a glycoprotein of 35% carbohydrate conte nt and apparent molecular mass of 55 kDa (SDS-PAGE and gel filtration) , Optima of temperature and pH were 50-60 degrees C and 6.0, respectiv ely. The enzyme activity was stable at 60 degrees C and exhibited a ha lf-life of 30 min at 70 degrees C. The enzyme hydrolyzed p-nitrophenyl beta-D-glucopyranoside, cellobiose, xylobiose, p-nitrophenyl beta-D-x ylopyranoside and CM-cellulose. Kinetic studies indicated that these s ubstrates were hydrolyzed at the same catalytic site.