Sustainable Grafting of (Ligno)Cellulose-Based Powders with Antibacterial Functionalities: Effect of Biomass Type and Synthesis Conditions

The problem of microbial resistance to antibiotics makes it necessary to develop new materials capable of overcoming the resistance to the chemicals currently used. Herein, the antibacterial properties of modified bamboo powder are tested and compared with modified cellulose isolated from soybean hulls. Such biomasses are functionalized in a water solution with (3-aminopropyl)triethoxysilane to introduce primary amino groups, and two different functionalization procedures are adopted: the first requires conventional heating steps, whereas the second implies microwave radiation use. The main outcomes from the characterizations evidence that the materials prepared with the thermal treatment are stabler than those obtained by the microwave-assisted procedure and that bamboo-derived samples react with the (3-aminopropyl)triethoxysilane through different functionalities other than hydroxyl groups. Finally, the antibacterial activity measured against Escherichia coli and Staphylococcus aureus shows that all the functionalized samples could efficiently remove Gram-positive and Gram-negative bacteria (removal > 93%). Moreover, active filters are realized by packing the material powders: when the bacterial inoculum passes through them in a continuous flow, some differences are observed between cellulose and bamboo-based materials, but the overall performances show that after 17 min and five recirculation cycles, both the samples reach an excellent Escherichia coli removal of about 100%.