Optimization and characterization of a biphasic solvent system for vinegar residue pretreatment: Enhanced fractionation efficiency, propionic acid production, and sustainability

Abstract

This study introduces a novel biphasic solvent system composed of phenoxyethanol and p-Toluenesulfonic acid (p-TsOH) for the pretreatment of vinegar residue (VR). The system achieves high cellulose retention (80.15 %) and effective removal of hemicellulose (97.10 %) and lignin (88.31 %) under mild conditions (127°C, 1.9 h). Structural changes in pretreated VR were analyzed, revealing significant improvements in enzymatic hydrolysis yield, achieving nearly 90 % conversion.The hydrolysate supports fermentation by Acidpropionibacterium jensenii, leading to efficient propionic acid production. The sugar-to-acid conversion rate of 28.15 % highlights the hydrolysate’s quality for lignocellulosic biotransformation. Density functional theory and molecular dynamics simulations confirm stable lignin interactions in the system, driven by hydrogen bonding, van der Waals forces, and π-π stacking, which promote lignin removal. Recycling phenoxyethanol over four cycles maintains high cellulose digestibility (84–95 %) and consistent delignification rates (88–89 %). The mass balance validated the efficient fractionation of biomass. A comprehensive analysis was conducted on the sustainability, safety, and environmental impact of the system. In conclusion, this study presents a novel biphasic solvent system that effectively fractions biomass, enhances solvent recovery, and reduces environmental impact. This system demonstrates broad applicability to different lignocellulosic biomasses, contributing to both economic and ecological sustainability.