The optimum solids loading obtained from the batch enzymatic
hydrolysis was 12%, which was set as the concentration for the
fed-batch process. Firstly, to identify the mode of adding enzyme,
fed-batch processes, ‘‘a’’ and ‘‘b’’ were carried out. 7% of fresh
substrates was fed after 6 h for a final solids loading of 19%, with
an enzyme loading of 10 FPU/ (g substrate) for both tests. For
‘‘a’’, all cellulase was completely added into the solution at the
beginning of hydrolysis according to 19% DM. In contrast, for
experiment ‘‘b’’, cellulase was added along with the corresponding
amount of substrate. Secondly, to further increase the concentration of reducing sugar, more fresh solids were fed and the final solids loading reached 33%. 21% solids were separated into different
amounts and fed to the enzymatic hydrolysis systems at different
times. The first feeding time was set at 6 h. And other feeding times
and feeding amounts of DM were determined. The other enzymatic