Comparative study on the properties of lignin isolated from different pretreated sugarcane bagasse and its inhibitory effects on enzymatic hydrolysis.

Five sugarcane bagasse lignin samples, namely, dilute sulfuric acid (DSAL), sodium hydroxide (SHL), ethanol (EL), hot liquid water (HLWL)-pretreated residual solids, and raw material (cellulolytic enzyme lignin, CEL), were extracted. Comparative studies on the physicochemical properties of isolated lignin, nonproductive adsorption of cellulase by lignin, and its effect on enzymatic hydrolysis was performed. Results showed that the molecular weight and homogeneity of lignin remarkably decreased after pretreatment compared with CEL. Lignin with low negative zeta potential, high phenolic hydroxyl group content and hydrophobicity exhibited strong nonproductive adsorption performance to cellulase. This phenomenon was positively correlated with it's inhibitory effect on enzymatic hydrolysis. Compared with the control (without lignin), the Avicel conversion rate (40 mg lignin/200 mg Avicel) decreased by 10.74%, 9.28%, 8.73%, 4.22%, and 2.80% after digestion of Avicel for 72 h with the presence of EL, SHL, CEL, HLWL, and DSAL, respectively.