3.3. Morphological structure of enzymatically treated
samples
Because the effectiveness of pretreatments in enhancing the
hydrolysis rate may be due to structural modification [26], scanning
electronic microscopies of the different BSG samples were
obtained to verify the material structural changes caused by
the pretreatments. Note that untreated BSG exhibited rigid and
highly ordered fibrils (Fig. 2A). The hemicellulose removal
modified the material structure, but the main structure was not
broken down (Fig. 2C). When the lignin was also removed
(Fig. 2E), the material structure was strongly modified resulting
in a structure very different from the other two, untreated and
cellulignin. In this case the cellulose fibers were separated from
the initial connected structure and fully exposed, thus increasing
the external surface area and the porosity. Consequently, these
fibers were more susceptible to the enzymatic attack than those
of the other two BSG samples. This is in agreement with the
findings of Ooshima et al. [29], who observed that more severe
pretreatment caused an increase in the surface area of cellulose
available to enzyme.