Insights into the chemical structure and composition of bio-based deep eutectic solvent (DES) in biomass pretreatment

A renewable and effective system has been developed for biomass conversion. Approaches using deep eutectic solvents (DESs) have emerged as a novel solvent to separate and extract useful components in various areas, achieving a successful techno-economy. The combinations of hydrogen bonding acceptor (HBA) and hydrogen bonding donor (HBD) determine the quality of biomass pretreatment. Among them, bio-based DESs have been investigated as promising agents to fractionate the biomass component. The methoxy groups are present in various types of natural phenolic structures, which can be derived from lignin. Therefore, in this study, the bio-based DESs containing the methoxy-substituted phenols were tested for biomass pretreatment. The thermal properties of DESs were measured with differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The rheometer was used to predict the viscosities of DESs. The correlations between the compositional and structural properties of HBDs and the DES pretreatment performance were investigated by analyzing physicochemical properties and composition as well as measuring the enzymatic digestibility of the biomass.