Multifunctional Bacterial Cellulose Films Enabled by Deep Eutectic Solvent-Extracted Lignin

Inspired by natural plant cells, lignin is utilized as a filler and a functional agent to modify bacterial cellulose (BC). By mimicking the lignin-carbohydrate structure, deep eutectic solvent (DES)-extracted lignin serves as a glue to strength the BC films and endows the films with diverse functionality. The lignin isolated by the DES (formed by choline chloride and lactic acid) is rich in phenol hydroxyl groups (5.5 mmol/g) and exhibits a narrow molecular weight distribution. A good interface compatibility can be obtained in the composite film, and lignin fills the void/gaps between BC fibrils. The integration of lignin endows the films with enhanced water-proof, mechanical, UV shielding, gas barrier, and antioxidant abilities. The BC/lignin composite film with 0.4 g of lignin addition (BL-0.4) exhibits an oxygen permeability and a water vapor transmission rate of 0.4 mL/m²/day/Pa and 0.9 g/m²/day, respectively. The multifunctional films are promising candidates for packing materials and exhibit a broad application prospect in the field of petroleum-based polymer replacement.