2.6. Extracellular Enzyme Activity and Aggregation Capacity

The extracellular enzyme activity of the strains was evaluated qualitatively using starch agar, CMC-Na agar, and skim milk agar, as described by Zhou et al. [32]. The presence of a halo or clear zone indicated a positive result.

Auto-aggregation and co-aggregation assays were described by Mustafa et al. [33]. The isolated strains were incubated in LB medium for 24 h at 37 °C and centrifuged at 5000 rpm for 10 min. The pellet was washed twice in phosphate-buffered saline (PBS) and then adjusted to a cell concentration of 10⁸ CFU/mL. The auto-aggregation rate was calculated as follows:

The isolated strains and V. parahaemolyticus were mixed for 10 s in a 15 mL conical tube, followed by incubation at 37 °C for 2 and 24 h. The co-aggregation rate was calculated as follows: