requires 2.4-fold more steam than from a 12% fermented broth [9].
Therefore, increasing the ethanol concentration is important to
decrease the energy consumed during distillation and dehydration;
this requires a high biomass loading. Nevertheless, a cellulosic substrate
is always of low density, and has strong hygroscopicity;
moreover, cellulosic slurries become progressively more paste-like
and difficult to handle at solid concentrations exceeding 15 wt%
[10]. This can be solved by using fed-batch SSF, in which a pretreated
substrate is fed continuously or by scheduled additions in
order to minimize the non-uniformity of the system [11]. A
fed-batch process has been applied successfully for enzymatic
saccharification and/or SSF of various pretreated substrates to
obtain relatively high concentrations of sugar and ethanol
[12–15]. Despite many advances in pretreatment technologies,
achieving an ethanol concentration of >5 wt% is challenging,
because the pretreated biomass loaded in the hydrolysis or SSF
process is relatively low.
This study aimed to investigate the enzymatic digestibility and
fermentability of pretreated Miscanthus, applied as a high-concentration
biomass in SSF, using a continuous feeding system connected
to the bottom of the bioreactor and a particular type of
impeller.