The TEM image of the nanofiber suspension subjected to ET
evidenced less pure nanofibers and bundles as compared with the
suspension obtained by CT. On the basis of the study by Pelissari
et al. (2014), incomplete hemicelluloses and lignin removal during
treatment and interfibrillar hydrogen bonds formation
accounted for the residual nanofiber bundles. ET did not remove
these amorphous components as effectively as CT, which generated
a barrier of cementing materials around the fiber bundles and
hindered enzyme penetration into the cellulose chains. Consequently,
impurities and bundles existed in the CNFs isolated by ET.
Treatment with xylanase partially removed hemicelluloses. This
happened because this enzyme usually removes the xylan fraction,
since it has specific action and works mainly to degrade hemicelluloses
to soluble oligosaccharides (Hassan et al., 2010).