An Antibacterial and Toughening Strategy Based on Carbonaceous Nano-Lamellae Applying for Food Preservation

Integrating walnut green husk-derived carbonaceous nano-lamellae (WCNL) into casein films (CF) addresses the challenge of combining mechanical strength, barrier performance, and antibacterial activity in sustainable food packaging. The hydrothermally synthesized WCNL features defect-rich hierarchical networks that induces strong interfacial hydrogen bonding, creating a nano-confined network, which dramatically improves mechanical strength (563% increase in tensile strength) and reduces water vapor permeability by 22.77% of CF-WCNL, while offering excellent UV shielding and antioxidant activity. Standardized colony-counting assays demonstrated antibacterial efficiencies approaching 100% against both E. coli and S. aureus under the tested conditions. Time-kill kinetic analysis and live/dead fluorescence staining further reveal a pronounced time-dependent loss of bacterial viability, supporting a bactericidal rather than merely bacteriostatic effect. It is posited that the antibacterial behavior may be comprised of multiple concurrent processes, including edge-mediated membrane disruption, physical immobilization by the interconnected WCNL architecture, and ROS-induced oxidative stress. This hypothesis is supported by bacterial morphological observations and ROS analyses. These findings demonstrate the potential of biomass-derived carbonaceous nano-lamellae for developing mechanically robust and multifunctional bio-based food-packaging films.