Enhancement of cellulose conversion efficiency in corn straw via lignin modification using 2-hydroxy-1-naphthoic acid (2H1NA)-assisted dilute acid pretreatment

During dilute acid pretreatment of lignocellulosic materials, condensation reactions of lignin lead to non-productive adsorption of cellulase, which hinders the enzymatic conversion of cellulose. In this study, 2-naphthol and its derivatives were employed to assist the dilute acid pretreatment of corn straw, markedly improving cellulose conversion efficiency. In particular, the dilute acid pretreatment method assisted by 2-hydroxy-1-naphthoic acid (2H1NA) achieved a cellulose conversion rate of 79.05%, which was 47.02% higher than that of unassisted dilute acid pretreatment. The chemical composition, surface structure and cellulose accessibility analyses of the pretreated corn straw demonstrated that 2H1NA-assisted pretreatment reduced the surface lignin content, promoted lignin removal and improved cellulose accessibility. According to heteronuclear single quantum coherence (HSQC) and 31 P nuclear magnetic resonance (NMR) analyses of the residual lignin, the addition of 2H1NA reduced the contents of β-O-4, β-β, and β-5 linkages, accompanied by elevated carboxyl group content in lignin. These changes confirmed the incorporation of the additive into the structure of lignin during the pretreatment process, which effectively impeded lignin repolymerization. Overall, this work offers a feasible strategy for targeted lignin modification in agricultural wastes such as corn straw to achieve efficient biomass conversion.