High processing cost is still the major technical barrier to cellulosic ethanol production at commercial scales (Lynd et al., 2008).
One reason for the high cost is the high steam energy consumption
in the distillation of fermentation broth with low ethanol titer
when lignocellulose materials are used as feedstock (Galbe et al.,
2007). Increasing the cellulose content in the fermentation system
is a direct way for increasing ethanol titer and the utilization of the
lignocellulose material with high cellulose content is a proper
option