Cellulases from Chaetomium thermophile var. dissitum.

Abstract

When cultivated in a liquid medium with cellulose, Chaetomium thermophile var. dissitum produced extracellular cellulolytic enzymes. By concentration of the culture filtrate, followed by ion‐exchange chromatography on DEAE‐Sephadex A‐50 and gel filtration on Biogel P‐100, three electrophoretically pure components were obtained. Of these, one was a typical Cx enzyme (endoglucanase) causing rapid decrease of the viscosity of carboxymethylcellulose solutions, while showing low effect on native cellulose.The other was active towards native cellulose, but had little effect on the viscosity of carboxymethylcellulose. It is concluded that this enzyme is an exoglucanase (C1 enzyme), possibly a cellobiohydrolase.The third component showed only cellobiase (β‐glucosidase) activity, and had no effect on cotton or carboxymethylcellulose. The three components, when mixed, showed synergistic effects on highly ordered cellulose. The endo‐ and exoglucanases were characterized with regard to molecular size and iso‐electric point (pI). Both cellulases had pI near 4.55, but their molecular weights were different: 67 000 (exoglucanase) and 41 000 (endoglucanase). The effect of temperature on the activity of the cellulases was examined with both cotton and carboxymethylcellulose as substrate. Arrhenius activation energies, Q10, and temperature optima for the different reactions were determined.