that with 3% NaOH. Higher NaOH concentrations and longer pretreatment
times during the pretreatment resulted in lower solid
recovery, although they had higher lignin removal (Table 1), thus
leading to less reducing sugars yield. As shown in figure, hot water
pretreatment (control) of CBG at 121 C did not work at all with regards
to enhancing sugar yield. Based on this experiment, the highest
total reducing sugar yield (approximately 77% of the theoretical
maximum) was obtained with 1% NaOH for a pretreatment time of
30 min. The pretreated CBG with 0.5% NaOH had much lower
digestibility than that with 0.75% and 1% NaOH, simply due to
the significantly less lignin removal for pretreatments with 0.5%
NaOH. Although pretreatments with 1% NaOH gave significantly
higher lignin removal than those with 0.75% NaOH, no statistical
difference in sugar yield was observed among the pretreatments
with 0.75% and 1% NaOH for 15 and 30 min.
Analyses of glucose and xylose yields after hydrolysis were
summarized in Table 2. It was noted that the overall glucan conversion
efficiency slightly decreased as pretreatment time and
NaOH concentration increased. Comparing the total reducing sugar
production in Fig. 1 and overall yield of xylose in Table 2, it was noticed
that the amount of reducing sugar released after hydrolysis
was highly associated with the xylose yield. With the increase of
NaOH concentration from 1% to 3%, the overall xylose yield was
significantly reduced while the overall glucose yield was fairly constant