Encapsulation of Phage Cocktail

The encapsulation of a phage cocktail—S4lw and D5lw—was conducted as previously described with minor modification^{29 (link)}. First, phages S4lw and D5lw at approximately 10⁹ PFU/mL were mixed together at a 1:1 ratio as a phage cocktail. A total of 100 mL of phage cocktail in SM buffer was added with 0.02 M Na₂CO₃ (Sigma-Aldrich, Oakville, Ontario, Canada) and around 1.2—1.8% sodium alginate (Buchi, Switzerland), depending on nozzle sizes used for the encapsulation. After alginate was dissolved, the phage-alginate mixture was subject to encapsulation using a Buchi B-390 encapsulator (Buchi, Switzerland) with different nozzle sizes (200, 300, 450, 750, and 1000 μm) accordingly. At the same time, a clean beaker containing 200 mL of 1.8% CaCl₂ (Sigma-Aldrich, Oakville, Ontario, Canada) with a low-rate spinning stir bar was used to catch and harden the resulting phage-encapsulated beads from the encapsulator. After solidifying, the beads were separated from the solution and washed with SM buffer (three times) to remove any free phages. The beads were stored in the SM buffer at 4 °C for further experiments.