Analyses of untreated pretreated solid biomass and
The enzymatic hydrolysis of OS pretreated hemp hurds was performed using the industrial cellulase blend CTec2. As given in Table 3, OS pretreatment increased enzymatic susceptibility of residual solids as a function of the CS. An almost eightfold increase in glucan to VTP-27999 conversion, compared to untreated hemp hurds, was achieved at CS 1.7. Although the highest glucan hydrolysis was observed for the CS 1.7, maximum overall glucose recovery (66.0%) was obtained from CS 1.3. This was due to the higher residual solids recovery obtained (Table 1). Interestingly, as seen in Fig. 2, enzymatic hydrolysis showed a linear increase when AIL was reduced from 25 to 13%, while a further delignification did not improve hydrolysis. Even though it is well known that lignin impedes enzyme access to glucan chains by unproductive binding and steric hindrance (Chang and Holtzapple, 2000), according to our results, only 50–60% of lignin should be removed from hemp hurds to obtain high levels of hydrolysis by CTec2. Although other authors stated the need of higher delignification degrees, to achieve satisfactory enzymatic hydrolysis levels (Choi et al., 2013 and Siqueira et al., 2013), the extent of delignification required seems to be dependent on biomass source.