Toward Circular Bioplastics: A Holistic Reinforcement Strategy for Functional Chitosan Films Using Lignin, Cellulose, and Chitin Nanocrystals

Abstract

The development of biodegradable packaging from renewable resources has become a central focus for both academia and industry. Marine crustacean waste constitutes an abundant source of chitin for the production of sustainable packaging materials. However, designing chitosan-based bioplastics that are simultaneously multifunctional, mechanically robust, water-resistant, and environmentally compatible remains a significant challenge. Herein, we explore the use of cellulose nanocrystals (CNCs), chitosan nanocrystals (ChNCs), and lignin nanoparticles (LNPs), as reinforcement agents for violacein-containing chitosan bioplastics. All nanofillers improved the dispersion of violacein within the chitosan matrix, with CNC markedly enhancing mechanical properties (tensile strength of 68 MPa), ChNC promoting antibacterial activity (significant reductions of ∼2.01 log(CFU/mL) for Staphylocossus aureus and ∼2.11 log(CFU/mL) for Esherichia coli), and LNP imparting strong antioxidant properties (up to 57.7% antioxidant activity). Building on these findings, we next crafted ternary-reinforced nanocomposite films incorporating all three nanofillers. The resulting holistic bioplastic, referred to as CS@Vio^3%-(CNC_ChNC_LNP)-f, exhibited a complementary combination of properties, with concurrent improvements in mechanical strength, antibacterial efficacy, and antioxidant activity. Beyond supporting circular economy principles through the valorization of bio-based resources, this work provides a holistic strategy for designing high-performance chitosan-based packaging materials.