ABSTRACT
The mechanism of alkaline hydrolysis is believed to be
saponification of intermolecular ester bonds cross-
linking lignin and carbohydrates (e.g., arabinoxylans).
The porosity of the lignocellulosic material increases
with the removal of the cross-links. The major effect of
the alkali pretreatment is the removal of lignin, thereby
improving the reactivity of the remaining polysacchar-
ides. Sodium hydroxide is the most studied alkali among
sodium, potassium, calcium, and ammonium hydroxides;
lime; and hydrogen peroxide used as pretreatment
agents. Saccharification is enhanced as a result of
delignification and structural swelling, increase of the
internal area, and reduction in the degree of polymeriza-
tion and crystallinity. Rice straw pretreated with 2%
NaOH at 85C for 60 minutes with 1:4 solid-to-liquid ratio[3] results in an increase of cellulose by 54.83% and
a decrease in hemicellulose and lignin by 61.07% and
36.24%, respectively.
