Unraveling lignin extraction: molecular dynamics insights into effective biomass valorization using a p-toluenesulfonic acid/solvents system

Abstract

Extraction of native-like lignin from lignocellulose is crucial for maximizing the value of all three major components of biomass. In this study, molecular dynamics was employed to reveal the essence of lignin condensation during the pretreatment of biomass with a promising acidic hydrotropic solution (AHS) at the molecular level. Diols were discovered to effectively suppress the excessive acidity of p-toluenesulfonic acid (pTsOH) in AHS while maintaining its solubilizing effect below a minimal hydrotropic concentration (MHC). The experimental results confirmed that the combined use of 1,4-butanediol and pTsOH can extract native-like lignin under mild conditions. The retention of lignin's β-O-4 linkages can exceed 90%, and the lignin extraction rate was over 80%. The obtained lignin can enhance the efficacy of chemical sunscreens, doubling the sun protection factor (SPF). Simultaneously, the residual cellulose was readily hydrolyzed into glucose by cellulase. This strategy demonstrates excellent adaptability to various biomass sources, including herbaceous species, hardwoods, and highly recalcitrant softwoods. The work lays the theoretical foundation for the precise control of biomass component separation using AHS, contributing to the development of mild and efficient component separation technologies in the future.