3.2. Effect of NaOH pretreatment on compositional changes of CBG
Lignin removal during sodium hydroxide pretreatment of CBG is
shown in Table 1. Pretreatment time of 30 min was sufficient to
achieve a significant amount of total lignin removal as long as the
sodium hydroxide concentration was equal or over 1%. On the other
hand, decreasing sodium hydroxide concentration from 1% to 0.5%
significantly reduced total lignin removal, but there was no significant
difference in lignin removal between 2% and 3% NaOH.
Unlike lignin, glucan content of CBG decreased by a fairly small
percentage (less than 10%) during sodium hydroxide pretreatment.
Hemicellulose solubilization displayed an obvious difference from
cellulose degradation during sodium hydroxide pretreatment of
CBG, mainly because hemicellulose is more vulnerable by chemical
pretreatments than cellulose (Schmidt and Thomsen, 1998). The
results indicate that lignin removal and xylan degradation account
for the major parts of total solid loss during sodium hydroxide pretreatment
of CBG.