4.7. Thermal, pH, and Chloroform Stability Tests

The phage suspensions in normal saline with a titer of 5 × 10⁷ were incubated at various temperatures (0 to 80 °C) and aliquot (100 μL) were collected after 1 h, respectively. Then, the double-layer agar and spot test were used to evaluate the thermal stability of Henu2. To evaluate the pH stability of the Henu2 phage, the pH of the phage buffer was adjusted in wide range from 2 to 12. After incubating at 30 °C for 1 h, the amount of phage Henu2 was diluted and two-layer agar method was used to count the phage titer. To test the effect of chloroform, 10 μL chloroform was added to 1ml of Henu2 suspension with a titer of 1 × 10⁶. The solution was gently mixed and incubated for 1 h at room temperature. Then, the phage titer was determined by the double agar-layer agar method. Phage Henu2 was exposed to UV at 50 J/m². The titer was determined every 10 min for 2 h using the double agar-layer agar method. A total of 3 replicates were performed.