Abstract
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-enrloglucanases).
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.
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