Increased CNFs degree of crystallinity stems from partial
hemicelluloses and lignin elimination from the fiber during the
alkali and bleaching pretreatment steps. CNFs isolation involved
either acid or enzymatic hydrolysis, and these steps removed
amorphous cellulosic domains (Siqueira et al., 2010a). The higher
crystallinity of the CT-treated CNFs was a consequence of the
bleaching step, which removed most of the lignin present in the bran. Mussatto, Fernandes, Milagres, and Roberto (2008) stated
that removal of hemicelluloses and lignin fractions extensively
altered the structure of natural fibers, increasing the crystal surface
area and the accessibility of the hydrolytic agent to the cellulose.
The bran sample crystallinity improved by 300 and 200% after CT
and ET, respectively.