4A and B, the glucose conversion was not affected significantly in the presence of the Tween 80 when the enzyme loading and hydrolysis time were varied (P = 0.05). This indicates that xylose might be the major factor limiting enzymatic hydrolysis. For the extruded corncobs with 80% xylose removal, the see more effect of Tween 80 was very small at 24 h ( Fig. 4C). However, when the hydrolysis time was prolonged to 72 h ( Fig. 4D), increasing Tween 80 concentration resulted in a significant increase in glucose conversion at a high level of enzyme

loading (P < 0.05). However as the hydrolysis time increases it would be expected to see a decrease of the hydrolysis rate due to cellulosic substrate decrease, increase of potentially inhibitory end- and by-products and general I-BET-762 concentration enzyme deactivation [13]; potentially more evident at low enzyme loadings. The plot shows that a higher hydrolysis yield was obtained in the presence of a high level of Tween 80 concentration. For example, the difference in the glucose conversion was changed from 36% to 42% when the enzyme loading was 2%, and a higher difference was obtained from 80% to 88% when the Tween 80 concentration increased to 6% at an enzyme loading of 8%. In addition,

the surfactant also could prevent the unproductive binding of cellulase to lignin by absorbing into the surface of lignin. This enabled the more active enzyme to only react with cellulose to improve the glucose conversion [10]. The combined effect of enzyme loading and hydrolysis time at fixed Tween 80 concentration (3%) is shown in Fig. 5. As can be seen from Fig. 5A, the conversion of glucose PD-1 inhibitor increased from 22% to 29% at an enzyme loading of 2% with extruded corncobs with 7% xylose removal, but increased from 51% to 68% at 8% enzyme loading when increasing hydrolysis time from 24 to 72 h. The effects of hydrolysis time on the glucose conversion of extruded corncobs with 80% xylose removal were also observed (Fig. 5B). When enzyme loading was at 2%, glucose conversion was only 28% at the hydrolysis time of 24 h. Increasing the amount of cellulase significantly

improved the glucose conversion to 59% when enzyme loading increased from 2% to 8%. Enzyme crowding on the cellulose surface, an effect that can result in lower hydrolysis rates at increasing enzyme concentrations [37], was not observed under the experimental conditions. An increase in hydrolysis time from 24 to 72 h at 2% enzyme loading only resulted in a slight increase in the glucose conversion. This might be due to not enough cellulase reaching adsorption saturation for a certain amount of cellulose hydrolysis in the reaction mixture. Further increases in the enzyme loading would slow down the glucose conversion due to more unused cellulase in the mixture solution. Thus, as expected, glucose conversion could be increased with longer hydrolysis times at a higher enzyme loading.