Multiscale analysis reveals cellulose structural features as primary determinants in bamboo (Dendrocalamus farinosus) cell wall recalcitrance

Abstract

Bamboo represents a promising energy crop; however, its industrial utilization is limited by the complex recalcitrance of its cell walls. A comprehensive understanding of bamboo recalcitrance mechanisms and their biosynthetic regulation is essential for efficient lignocellulosic conversion. Here, we employed paraffin sectioning, confocal Raman imaging, 2D HSQC NMR, and transcriptomic profiling to investigate the recalcitrance dynamics across different developmental stages and strains of D. farinosus. The results revealed that enhanced recalcitrance is primarily attributed to the migration of high-concentration enzymatic substrates and increased cell wall compactness. Additionally, lignin polymerization and the formation of C-C bonds contribute to resistance, whereas increased hemicellulose side chains tend to weaken recalcitrance. Cellulose structure emerged as the core determinant of recalcitrance, with increased cellulose crystallinity (XK8 increased by −4.5 %, XK12 increased by 16.4 %, XK23 increased by 31.9 %) significantly enhancing recalcitrance. This indicates that cellulose structure defines the recalcitrance of D. farinosus. Transcriptomic analysis further demonstrated that upregulated structural polysaccharide biosynthesis pathways may enhance cellulose crystallinity, thereby reducing enzymatic saccharification efficiency. Notably, Deep Eutectic Solvent (DES) treatment reconstructed cellulose matrices, significantly weakening recalcitrance. These findings provide a theoretical foundation for breeding low-recalcitrance bamboo germplasms and advancing bamboo biorefinery technologies.