Pulsed electric field-assisted biorefinery of soybean hulls for sequential recovery of phenolics, proteins, cellulose, hemicellulose and lignin

Lignocellulosic biomass recalcitrance remains one of the main barriers to the development of efficient integrated biorefineries. In this study, pulsed electric fields (PEF) were investigated as a structural pretreatment to enhance the sequential fractionation of soybean hulls into phenolics, proteins, pectin-related fractions, cellulose, hemicellulose, and lignin. PEF was applied at electric field strengths of 0.5-2 kV/cm prior to a sequential extraction process involving hydroethanolic extraction, citric acid extraction, and alkaline delignification. PEF significantly increased the extraction of pectin (up to 55%) and proteins (up to 61%) and improved phenolic recovery by enhancing mass transfer during hydroethanolic extraction. Structural analyses (FTIR, SEM, and TGA) indicated that PEF promoted partial disorganization of the lignocellulosic matrix and weakened lignin-carbohydrate interactions, increasing the accessibility of amorphous fractions while largely preserving cellulose structure and thermal stability. Moderate electric field strength (1 kV/cm) provided the best balance between fraction recovery and structural preservation. These results demonstrate that PEF reduces biomass recalcitrance without compromising the structural integrity of the polysaccharide matrix, acting as a mild structural pretreatment that improves the efficiency and selectivity of sequential lignocellulosic fractionation. This approach reinforces the potential of PEF as an enabling technology for carbohydrate-oriented biorefinery platforms.