Structural Changes in Lignin During Different Pretreatment Ways of Bamboo Biomass and the Effect on Enzymatic Hydrolysis

Bamboo biomass is a renewable feedstock for biorefinery and value-added applications in many areas. As a potential raw material for phenol monomer and polymer resin, lignin is a key block material in the hydrolysis of lignocellulose and needs to be investigated. In this study, p-TsOH (p-toluenesulfonic acid), DES (Deep eutectic solvent) and CAOSA (cooking with active oxygen and solid alkali) pretreatment were used to extract lignin from bamboo biomass, and the effect of pretreatment on lignin structure was compared by FT-IR, TGA, GPC and NMR. The results implied that the average molecular weight (AMW) of lignin fractions reduced with the increase of pretreatment temperature in all the processes. 2D-HSQC illustrated that the β-O-4 linkages, Aα and Aβ(G) of all the lignin fractions were obviously broken. Lignin extracted with p-TsOH at 110 ℃ only possesses methoxy group, Aγ and Cγ units. The content of aliphatic hydroxyl group in lignin extracted by DES was higher. The lignin extracted by CAOSA exhibited lower molecular weight and narrow (PDI) polydispersities (1.49~1.25). After CAOSA treatment, the glucose concentration after cellulase hydrolysis is 14.3 g/L and the efficiency is 95.57%.