Abstract
Properties of hemolysin produced by β-hemolytic Streptococcus sp., isolated from yellowtail (Seriola quinqueradiata) were investigated using the culture supernatant. The hemolytic activity of the toxin against sheep red blood cells reached a maximum after incubation at 25°C for 90 min or at 37 or 50°C for 30 min. The toxin showed higher activity at pH 5.5-6.0 and was intensively inactivated by papain and subtilisin (Bacillus subtilis protease) but was only slightly inhibited by pepsin and β-amylase. Sheep red blood cells were more sensitive to the toxin than rabbit, white-spotted char (Salvelinus leucomaenis) and rainbow trout (Oncorhynchus mykiss) red blood cells.
