Mechanically Mediated Enzymatic Saccharification of Lignocellulosic Biomass: From Fundamental Mechanisms to Process Intensification
Mechanical force offers a distinctive nonequilibrium mode of energy input for lignocellulosic biomass valorization through localized, transient action. This review systematically examines the multiscale physicochemical effects of mechanical force, its synergistic coupling with chemical pretreatments, and its role in enhancing enzymatic hydrolysis. The principal contribution of mechanical force is not merely particle-size reduction, but the exposure of active sites and improvement in substrate accessibility at the molecular level. Coupling mechanical force with chemical pretreatment enables the efficient component fractionation under mild conditions while mitigating irreversible lignin condensation. In high-solids enzymatic hydrolysis, a periodic mechanical energy input can tear fiber bundles, release constrained water, and renew reaction interfaces, thereby allowing enzymes to sustain a high catalytic efficiency at extremely low liquid-to-solid ratios and reducing the dependence on large amounts of free water. An economic analysis indicates that feedstock and enzyme costs dominate the overall process economics. Accordingly, mechanical-force strategies should prioritize the maximized sugar yield and reduced enzyme loading under a controlled energy input. Future research should focus on continuous operation, the balance between mechanical deconstruction and lignin structural integrity, and multidimensional evaluation frameworks that integrate the energy consumption, sugar yield, enzyme dosage, and full-process energy balance.