Impact of Lignin Content on the Sweet Sorghum Bagasse Enzymatic Hydrolysis

Lignin has been considered as an important factor to effect the enzymatic hydrolysis of lignocellulose. In this study, impact of lignin content on enzymatic hydrolysis was investigated using sweet sorghum bagasse (SSB) delignified by NaOH or Ca(OH)(2) pretreatment. For NaOH pretreated samples, a negative correlation between cellulose conversion rate and the residual lignin content has been found when the lignin content is between 18.93 % and 8.72 %. Further delignification of sample can't increase efficiency of enzymatic hydrolysis anymore. For Ca(OH)(2) pretreatment, there is no correlation between lignin content and cellulose conversion rate. More interesting is that the lignin content of SSB pretreated with 10 % NaOH (17.32 %) is closed to that pretreated with 10 % Ca(OH)(2) (16.42 %), but the cellulose conversion rate of the latter was 1.71 times of the former. While the surface lignin content of 10 % NaOH pretreated SSB was 1.52 times higher than Ca(OH)(2) pretreated SSB. These results demonstrated that the impact of lignin content on enzymatic hydrolysis of NaOH and Ca(OH)(2) pretreated SSB was different. The lignin removal is mainly contributed to the enzymatic hydrolysis of SSB treated with NaOH, while the contribution of Ca(OH)(2) to the enzymatic hydrolysis of SSB was complex and needed to be studied further. (C) 2014 The Authors. Published by Elsevier Ltd.