Sustainable and multifunctional cellulose-lignin films with excellent antibacterial and UV-shielding for active food packaging

The natural biopolymers hold substantial prospects as food packaging materials due to the integrated advantages of excellent film-forming properties, biodegradability and appropriate mechanical properties. However, it remains a challenge to simultaneously endow antimicrobial, UV-shielding, water vapor and oxygen barrier properties of films. Herein, sustainable and multifunctional films were fabricated by constructing ε-polylysine (ε-PL) antimicrobial surface on the phenolated lignin/cellulose films (RCPL30). It is found that the fine control of electrostatic interactions and hydrogen bonding in anionic phenolated lignin/cellulose and cationic ε-PL is efficient for tailoring the structure and films performance. The addition of ε-PL effectively enhanced the antibacterial property, hydrophobicity, water vapor and oxygen barrier ability of the phenolated lignin/cellulose films. Antibacterial cellulose-lignin films with a high lignin content (30%) were developed. In particular, the bactericidal rate reached almost 100% when the ε-PL concentration was 3% (LRCPL30-3). The water vapor permeability and oxygen permeability of LRCPL30-3 were as low as (3.21 ± 0.06) × 10−11 g m−1 s−1 Pa−1, (4.15 ± 0.13) × 10−16 cm3 cm/cm2 s Pa, respectively. Moreover, the phenolated lignin provided an exceptional UV shielding properties (100% for UVB and 99.91% for UVA for LRCPL30-3 sample) with high thermal stability and antioxidant activities. More importantly, the as prepared LRCPL30-3 still showed high tensile strength (75.90 MPa). Based on these outstanding properties, LRCPL30-3 were used for shrimp package, which effectively extended shelf-life. Overall, the study highlights the benefits of biopolymers valorization and provides evidence of potential applicability of sustainable films (specially LRCPL30-3) as candidates for active food packaging.