Recent advances in hydrotropic solvent systems for lignocellulosic biomass utilization

In deconstructing lignocellulosic biomass, processing solvents directly and indirectly influence the process efficiency by reducing recalcitrance, fractionating target components, preserving/modifying biomass components, etc. Hydrotropic solvents have shown effective biomass fractionation performance due to their unique amphiphilic structure. In particular, these hydrotropes effectively separate lignin from the cellulose-rich fraction with minimum modification and maximum recovery, which aligns well with the biorefinery strategy by enhancing the recovered lignin quality and quantity. Hydrotropic solvent functions as a catalyst in biomass fractionation/degradation and also as a solvent via aggregation and clustering for the dissolution of target components such as lignin. Moreover, this solvent approach has great potential in eco-friendly manufacturing in plant biomass utilization because of aqueous processing. In this review, chemical structure, amphiphilicity, roles and mechanism of hydrotropic solvents are discussed along with their recent applications in plant biomass utilization. Current challenges in their industrial applications and perspectives on the direction of future research directions are presented. Hydrotropic solvents are a promising solvent in biomass processing due to their unique amphiphilic structure. This review summarizes recent advances in hydrotropic solvent systems with their chemical structure, amphiphilicity, roles, and mechanism.