Effect of structural changes of lignin during the microwave-assisted alkaline/ethanol pretreatment on cotton stalk for an effective enzymatic hydrolysis

Effective delignification of lignocellulosic biomass is an important factor to improve the efficiency of enzymatic hydrolysis and ensure the economic feasibility of bio-refining. Cotton stalk (CS) was treated by a microwave-assisted alkaline/ethanol pretreatment (MAAP) (at 160 degrees C for 15 min) process to separate high-purity lignin and digestible cellulose-rich residue. Results showed that the MAAP process resulted in homogeneous lignin fractions with narrow polydispersity index (PI), and the isolated lignin fragments exhibited relatively smaller molecular weights and numerous phenolic OH groups than those in MWL. The crystallization index of cellulose-rich substrates was increased after the MAAP integrated process. Meanwhile, the glucose yield of the integrated residue reached the maximum (82.41%) after enzymatic hydrolysis. The utilization of MAAP process was a beneficial and promising scheme for the generation of lignin fractions with satisfactory purity and chemical reactivity, which will facilitate the value-added application of CS in the future biorefinery. (C) 2022 Elsevier Ltd. All rights reserved.