Dependence of Enzymatic Saccharification on Residual Lignin Structure in Sugarcane Bagasse Pretreated with Alkaline Sulfite

摘要

Effects of residuaHignin structure—expressed as the syringaldehyde to vanillin (S/V) ratio—on the enzymatic saccharification rate was studied as a key step of bio-ethanol production. Alkaline sulfite-anthraqui-none (AS-AQ) and soda-AQ cooking methods were applied to delignification of sugarcane bagasse (SB) and oil palm trunk- (OPT), and the resulting pulp samples were subjected to enzymatic saccharification. The S/V ratios of residual lignin in the pulp were determined by the nitrobenzene oxidation method. This study showed that the AS-AQ method is more suitable for delignification of SB than the soda-AQ method is. SB pulp released more glucose than OPT pulp did under the same conditions of cooking and saccharification. A decrease in the kappa number (residual lignin content) significantly increased the saccharification, rate. In a comparison of AS-AQ pulp samples at the same kappa number (20), the SB pulp with a lower S/V ratio (0.68) yielded a higher saccharification rate (0.0327), whereas the OPT pulp (S/V ratio : 2.56) yielded a lower saccharification rate (0:0252). In a comparison of SB and OPT, we found that syringyl-rich lignin kept in pulp results in a lower saccharification rate of the pulp samples prepared by the AS-AQ cooking method.