초록
<P><B>Abstract</B></P> <P>Sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL) was applied to poplar NE222 chips in a range of chemical loadings, temperatures, and times. The combined hydrolysis factor (<I>CHF</I>) as a pretreatment severity accurately predicted xylan dissolution by SPORL. Good correlations between <I>CHF</I> and pretreated solids enzymatic digestibility, sugar yield, and the formations of furfural and acetic acid were obtained. Therefore, <I>CHF</I> was used to balance sugar yield with the formation of fermentation inhibitors for high titer ethanol production without detoxification. The results indicated that optimal sugar yield can be achieved at <I>CHF</I> =3.1, however, fermentation using un-detoxified whole slurries of NE222 pretreated at different severities by SPORL indicated <I>CHF</I> ≈2 produced best results. An ethanol titer of 41g/L was achieved at total solids of approximately 20wt% without detoxification with a low cellulase loading of 15FPU/g glucan (27mL/kg untreated wood).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Combined hydrolysis factor for optimizing sulfite pretreatment. </LI> <LI> High ethanol titer at 41g/L from poplar by sulfite without detoxification. </LI> <LI> Low cellulase loading of 15FPU/g glucan (27mL/kg wood). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>