The mode of action of two thermostable endoglucanases from Thermoascus aurantiacus and Clostridum thermocellum on CM-celulose with varying viscosities and ddegrees of substitution was studied. Both endoglucanages randomly attacked all the CM-celluloses tested, but the action of these two endoglucanases decreased with increasing degree of substitution (DS) of CM-cellulose. Thus, the DS rather than viscosity of CM-cellulose apperaed to influence the action of both endoglucanases. Further, HPLC analysis showed that the hydrolysis products released from all CM-celluoses were mainly unsubstituted cellobiose and cellotriose together with small amounts of higher cello-oligosaccharides. These results revealed that the endoglucanases not only attacked the glycosidic bonds between unsubstituted glucose residues, but also preferred less substituted CM-cellulose.
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