Unveiling the potential of water as a co-solvent in microwave-assisted delignification of sugarcane bagasse using ternary deep eutectic solvents.

Deep eutectic solvents (DESs) have become popular owing to their biodegradability and recyclability. In this study, the influence of water as a co-solvent is demonstrated to enhance the properties of choline based ternary DESs. A fast and energy-efficient microwave-assisted pre-treatment process was developed for delignification of sugarcane bagasse (SB). The effectiveness of SB fractionation was revealed by incorporating Lewis acids (MgCl2.6H20, NiCl2.6H20) with the DESs for pre-treatment and Choline chloride: Ethylene glycol: NiCl2.6H20 (CC:EG:NI) at a molar ratio 1:2:0.016 with 20w% water as a co-solvent provided the most promising result, with 84% delignification and 99% enzyme digestibility. Water was also employed as an anti-solvent to facilitate lignin solubility and exhibited up to 26w% lignin yield from DES liquor with maximum DES recovery of 95% (w/w). Water distinctly affects the density, viscosity, and intermolecular hydrogen bonding of the DES and its impact on the process dynamics is worth further exploration.

Improving enzymatic digestibility of sugarcane bagasse from different varieties of sugarcane using deep eutectic solvent pretreatment.

Sugarcane bagasse, a fundamental by-product of the sugar industry, was utilised to improve its digestibility for bioenergy applications. Choline chloride based deep eutectic solvents (DESs) were used for pretreatment of five different varieties of sugarcane bagasse (SRA1, SRA5, Q208, MA239, ISB) and a comparative study of compositional and morphological changes was performed. Three eutectic mixtures - choline chloride: malonic acid (1:1), choline chloride: glycerol (1:2) and choline chloride: lactic acid (1:5) were used to selectively remove lignin and improve saccharification efficiency. Physico-chemical characterizations performed using FE-SEM, FTIR, TGA and XRD analysis consistently indicated disruption of bagasse structure after DES pretreatment. Glucose recovery was predominantly influenced by the glucose content, as SRA1 variety showed the highest recovery of 92.8% for choline chloride: glycerol DES pretreatment. Choline chloride: lactic acid DES pretreatment demonstrated the most efficient lignin removal of 81.6% for ISB variety and the enzyme amenability was prominently increased to 98.5%.