Bacillus velezensis suppression on the growth of Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease in marine shrimp

This study evaluated the inhibitory function of probiotics isolated from three commercial products used in shrimp farming management. Five species of probiotics were isolated from the commercial products, which were B. subtilis, B. megaterium, B. velezensis, B. licheniformis, and B. amyloliquefaciens. The inhibitory function of the isolated probiotics on the growth of an acute hepatopancreatic necrosis disease (AHPND)-causing V. parahaemolyticus (VPAHPND), nonpathogenic V. parahaemolyticus, and Vibrio spp. isolated from shrimp farming samples were examined by disc diffusion and bacteriocin-like inhibitory substance test. Disc diffusion and bacteriocin-like inhibitory substance screening indicated that only B. velezensis could inhibit all Vibrio spp. Inhibitory efficiency of B. velezensis was further evaluated in the liquid media using the co-culture technique. With the assistance of a growth curve-monitoring system, we could examine multiple co-culture factors that affected the probiotic efficiency in the same experiment. The results demonstrated that the inhibitory efficiency of B. velezensis was increased with its concentration. The inhibitory efficiency of B. velezensis incubating in tryptic soy broth at pH 7.4 with 2% NaCl (TSB+) and Luria-Bertani broth at pH 7.4 with 1% NaCl (LB) was better than in alkaline peptone water broth at pH 8 with 2% NaCl (APW).