Strong and ductile cellulose film improved by the in situ incorporation of a genetically engineered protein conjugated synthetic polymer during bacterial cellulose growth

Bacterial cellulose (BC) has been extensively applied to fabricate advanced biomaterials, although it remains challenging due to its poor toughness and water stability. Herein a genetically engineered protein-conjugated synthetic polymer is designed to improve BC film's strength and flexibility. Initially, the hybrid polymer is constructed by grafting Family 3 carbohydrate-binding modules (CBM3) to amphoteric polyacrylamide polymer (AmPAM), one of the paper industry's most widely used dry-strength agents. Then, the conjugated polymer is added to the culture medium of BC growth, enabling it to incorporate into the matrix of cellulose chains. The results show that the BC film modified by CBM3-AmPAM exhibits superior mechanical properties, registering 9.94 % in strain and 13.8 MJ/m 3 in toughness, 12.1 and 8.0 folds over the sample with AmPAM addition only. Additionally, the BC film improved by CBM3-AmPAM has excellent gas resistance, thermal stability, and environmental endurance. The adsorption of CBM3-AmPAM on BC film revealed by quartz crystal microbalance with dissipation monitoring indicates that the adsorbed layer is thin and rigid, suggesting the strong interaction between the conjugated polymer and BC substrate. As a result of this reinforcing strategy, BC composites can be used in a wider range of applications.