2.6. Bactericidal Effect
The E. coli strain of KCTC 1039 was used as the test bacteria, cultivated in Luria-Bertani (LB) broth (Sigma-Aldrich, St. Louis, MO, USA) for 2 h at 250 rpm. For application of E. coli to respirator layers, 10 μL of bacterial culture, corresponding to ~5 × 106 CFU of E. coli (concentration; 5 × 108 CFU/mL), was injected into the center area of 2.5 cm × 2.5 cm of front side of a respirator, using a micropipette. The bacteria-loaded samples were subject to different disinfection treatments, and the CFUs of cells were quantified, using a staining method [39,40]. The quantification procedure is illustrated in Figure S2.