Simultaneous production of high activities of thermostable endoglucanase and beta-glucosidase by the wild thermophilic fungus Thermoascus aurantiacus

The culture-medium composition was optimised, on a shake-flask scale, for s imultaneous production of high activities of endoglucanase and beta-glucosi dase by Thermoascus aurantiacus using statistical factorial designs. The op timised medium containing 40.2 g l(-1) Solka Flee as the carbon source and 9 g l(-1) soymeal as the organic nitrogen source yielded 1130 nkat ml(-1) e ndoglucanase and 116 nkat ml(-1) beta-glucosidase activities after 264 h as shake cultures. In addition, good levels of beta-xylanase (3479 nkat ml(-1 )) and low levels of filter-paper cellulase, beta-xylosidase, alpha-L-arabi nofuranosidase, beta-mannanase, beta-mannosidase, alpha-galactosidase and b eta-galactosidase were detected. Batch fermentation in a 5-1 laboratory fer menter using the optimised medium allowed the production of 940 nkat ml(-1) endoglucanase and 102 nkat ml(-1) beta-glucosidase in 192 h. Endoglucanase and beta-glucosidase showed optimum activity at pH 4.5 and pH 5, respectiv ely, and they displayed optimum activity at 75 degrees C. Endoglucanase and beta-glucosidase showed good stability at pH values 4-8 and 4-7, respectiv ely, after a prolonged incubation (48 h at 50 degrees C). Endoglucanase had half-lives of 98 h at 70 degrees C and 4.1 h at 75 degrees C, while beta-g lucosidase had half-lives of 23.5 h at 70 degrees C and 1.7 h at 75 degrees C. Alkali-treated bagasse, steam-treated wheat straw, Solka flee and Sigma cell 50 were 66, 48.5, 33.5 and 14.4% hydrolysed by a crude enzyme complex of T. aurantiacus in 50 h.