Safety evaluation for the use of Bacillus amyloliquefaciens in freshwater fish cultures

Abstract

The primary objective of this work was to assess the effect of Bacillus amyloliquefaciens on the microbiota in polyculture tanks stocked with grass carp, gibel carp and sliver carp. The B. amyloliquefaciens showed high biosafety toward freshwater fish. The addition of B. amyloliquefaciens to the tanks significantly reduced ammonia, total nitrogen, total phosphorus and chemical oxygen demand (p ＜ 0.05) although nitrites increased (p ＜ 0.05). Bacterial diversity in the tanks was greatest in the un-inoculated tanks where Proteobacteria, Actinobacteria, Cyanobacteria, Verrucomicrobia and Bacteroidetes dominated. In the presence of added B. amyloliquefaciens, Proteobacteria and Bacteroidetes levels increased while Actinobacteria decreased. The classes and genera between controls and treatment groups differed although Bacillus levels did not increase in the inoculated tanks. We conclude that supplementation with B. amyloliquefaciens in aquaculture water had many advantages but also potential safety risks.