Mechanical gradient-guided separation of bamboo fibers and parenchyma cells via selective alkali-induced weakening of labile lignin linkages

Efficient separation of bamboo fibers and parenchyma cells is essential for sustainable utilization of lignocellulosic biomass, yet conventional non-selective processes cause substantial loss of parenchyma resources. The separation of bamboo fibers and parenchyma cells is fundamentally constrained by the structural heterogeneity of cell wall interfaces. Here we show that dilute alkali treatment selectively acts on the lignin–carbohydrate complex network in parenchyma cells, which is enriched in labile β-O-4 ether bonds and phenolic ester linkages, while preserving the more condensed structure of fiber cells. This molecular-level selective deconstruction induces a pronounced cell-scale mechanical gradient: the elastic modulus of parenchyma cell walls decreases from 8.35 to 3.14 GPa, whereas that of fiber cell walls remains at approximately 16 GPa. During subsequent hydraulic shearing, this mechanical heterogeneity directs crack propagation along weakened interfaces, enabling a transition from stochastic fracture to controllable cellular dissociation. The yields of both components increase by approximately 10% compared to conventional methods. This work establishes a direct causal link from molecular bond cleavage to macroscopic separation behavior, providing a paradigm for utilizing intrinsic structural heterogeneity rather than combating it. The recovered high-integrity fibers are well suited as discontinuous reinforcements in structural biocomposites, while the intact parenchyma cells can serve as bio-based microcarriers for controlled release. This mechanism-driven approach provides an efficient, low-consumption, and sustainable pathway for the high-value utilization of bamboo biomass.