THE CELLULASES ENDOGLUCANASE-I AND CELLOBIOHYDROLASE-II OF TRICHODERMA-REESEI ACT SYNERGISTICALLY TO SOLUBILIZE NATIVE COTTON CELLULOSE BUTNOT TO DECREASE ITS MOLECULAR-SIZE

Degradation of cotton cellulose by Trichoderma reesei endoglucanase I (EGI) and cellobiohydrolase II (CBHII) was investigated by analyzing t he insoluble cellulose fragments remaining after enzymatic hydrolysis, Changes in the molecular-size distribution of cellulose after attack by EGI, alone and in combination with CBHII, were determined by size e xclusion chromatography of the tricarbanilate derivatives, Cotton cell ulose incubated with EGI exhibited a single major peak, which with tim e shifted to progressively lower degrees of polymerization (DP; number of glucosyl residues per cellulose chain), In the later stages of deg radation (8 days), this peak was eventually centered over a DP of 200 to 300 and was accompanied by a second peak (DP, approximate to 15); a final weight loss of 34% was observed. Although CBHII solubilized app roximately 40% of bacterial microcrystalline cellulose, the cellobiohy drolase did not depolymerize or significantly hydrolyze native cotton cellulose, Furthermore, molecular-size distributions of cellulose incu bated with EGI together with CBHII did not differ from those attacked solely by EGI. However, a synergistic effect was observed in the reduc ing-sugar production by the cellulase mixture, From these results we c onclude that EGI of T. reesei degrades cotton cellulose by selectively cleaving through the microfibrils at the amorphous sites, whereas CBH II releases soluble sugars from the EGI-degraded cotton cellulose and from the more crystalline bacterial microcrystalline cellulose.