2.2. Bacterial culture preparation
E. coli K-12 was used as a testing organism for photocatalytic disinfection because it was safe to use and easy to grow. The bacterial cells were cultured in nutrient broth at 37 C and agitated at 200 rpm for 16 h. The cultures were then washed twice with 0.9% NaCl solution by centrifugation at 24,000 g for 5 min, and the cell pellet was re-suspended in saline solution. Finally, the cell concentration was adjusted to final cell density of 107 cfu mL-1 in the reaction mixture.