Dependence of the content of unsubstituted (cellulosic) regions in prehydrolysed xanthans on the rate of hydrolysis by Trichoderma reesei endoglucanase.

Removal of side chains from the bacterial polysaccharides xanthan and xylinan (acetan) results in the formation of unsubstituted cellulosic regions that are susceptible to hydrolysis by cellulases (beta-1,4-endoglucanases). In contrast to cellulose derivatives, low degrees of substitution (DS) may be obtained in xanthan without affecting the solubility in water, and longer unsubstituted regions are obtained for the same DS due to the regular distribution of side chains. By varying the fraction of cellobiosic residues carrying a side chain from 1.0 to 0.54, the viscosimetrically detected rate of hydrolysis by cellulase of conformationally disordered xanthan, increased by 4 orders of magnitude. An increase was also obtained by removing side chains from xylinan. An analysis of the kinetic data suggests that very long unsubstituted regions (more than 10 glucose residues) are required for maximum rate of hydrolysis by cellulase.