2.4. Antibacterial tests
Approximatively 74 x 106 colony forming units CFU.mL−1 of each bacteria species (E. coli andB. subtilis 168) with a cell density of 0.5 at 600 nm was loaded on LBA plates. The antimicrobial behavior of the as-prepared samples was evaluated by diffusion and zone Inhibitory tests towards E. coliand B. subtilis bacterial strains. The assay is a semi-quantitative method where samples (1-9 mg) containing silver or copper metal were put in direct contact on LBA plate pre-seeded by bacteria strains. Negative controls were included in each assay. After 24 h of incubation at 37 °C, the diffusion zone where bacteria proliferation was inhibited was measured. The antibacterial property was evaluated by the application of 5 mg (Organoclays) or 1×0.5 mm2 (CT) of the synthesized clay-based materials or tissue of cellulose-based samples, respectively. All experiments were performed in triplicate (three independent growth cultures) with at least two technical replicates.