4-hydroxybenzoic acid-assisted formic acid preserves lignin structure during efficient hemicellulose removal in bamboo biorefinery

This study developed a technology for pretreating bamboo biomass using a synergistic system of 4-hydroxybenzoic acid (4-HA) and formic acid (FA). By optimizing reaction temperature, reaction time, and acid concentration parameters, the bamboo hemicellulose removal yield of 99.53% was achieved, whilst glucose and lignin removal yield were only 9.28% and 9.69%, respectively. Characterization results indicated that the surface morphology of the pretreated solid residue exhibited disordered features, with significantly enhanced crystallinity and thermal stability. Subsequent experiments with model lignin compounds confirmed that 4-HA addition effectively inhibited lignin degradation. Nuclear magnetic resonance (NMR) analysis indicated reductions in S and G units alongside an increase in H units. Combining density functional theory (DFT) calculations with molecular dynamics simulations (MDS) elucidated the synergistic mechanism of 4-HA and FA in hemicellulose removal and lignin depolymerization inhibition. Enzymatic hydrolysis achieved separation of the three major components. This strategy offered novel insights for precise hemicellulose removal during biorefinery.