Mild fractionation of sugarcane bagasse into fermentable sugars and β-O-4 linkage-rich lignin based on acid-catalysed crude glycerol pretreatment

Acid-catalysed crude glycerol (ACG) pretreatment was carried out at 110 degrees C and 130 degrees C for mild fractionation of sugarcane bagasse into fermentable sugars and high-quality lignin. ACG pretreatment at 110 degrees C led to sugar yields of 71%-74%, comparable to those with acid-catalysed reagent-grade glycerol (AG). ACG pretreatment removed more lignin (53%-75%) than AG pretreatment (38%-49%), likely due to the presence of organic impurities in ACG. Hence, 28% more lignin was recovered from ACG pretreatment hydrolysate than with the AG pretreatment. NMR analysis revealed that recovered lignin was modified by glycerol through etherification of beta aryl ethers and esterification of hydroxycinnamic acids, which prevented lignin condensation and led to the generation of beta-O-4 linkage-rich lignin at mild conditions (110 degrees C for 3 h and 5 h). This study suggests that crude glycerol is a suitable low-cost solvent for mild fractionation of lignocellulosic biomass into fermentable sugars and high-quality lignin for value-adding applications.