Closed-loop valorization of bamboo agro-waste into multifunctional cellulose–pullulan films for active food packaging

This study upcycles bamboo shoot–shell waste into cellulose and nitrogen-doped carbon dots and co-assembles them with pullulan to form multifunctional PCN films, establishing a one-material, dual-use, closed-loop route for sustainable packaging. Nitrogen doping strengthens hydrogen-bonding and electronic interactions with the polysaccharide matrix, evidenced by FTIR redshifts and SEM-observed densification. Rheology shows shear-thinning flow and enhanced viscoelasticity, with an optimum at 5 wt% NCDs. At this loading, the films reach a tensile strength of ∼42 MPa, which exceeds typical biopolymer ranges, and they exhibit improved barrier performance, slightly higher hydrophobicity, and robust UV blocking below 400 nm. Antibacterial assays reveal >96% inhibition of Escherichia coli and ∼99% of Staphylococcus aureus . SEM reveals contact-induced envelope damage, and light-dependent assays confirm a photooxidative pathway. The films are non-cytotoxic to L929 fibroblasts and biodegrade rapidly in soil-simulating tests, achieving >98% mass loss within 12 days. As active packaging, they extend strawberry shelf life by reducing weight loss, suppressing microbial growth, and preserving acidity, vitamin C, and soluble solids. This bamboo-derived synthesis strategy combines high performance, cytocompatibility, and rapid biodegradation, exemplifying a one-material, dual-use, closed-loop valorization of agricultural residues for sustainable food packaging. • Closed-loop upcycling of bamboo shells into cellulose and N-doped carbon dots. • One-material, dual-use route yields strong PCN films. • Robust UV blocking, improved barriers, and L929 cytocompatibility. • Antibacterial: E. coli >96%, S. aureus ∼99%; photooxidation confirmed. • Fast biodegradation and extended strawberry shelf life.