Isolation, identification and characterization of two strains of Bacillus subtilis

Objective  To explore potential probiotics in order to develop microecological agents for aquiculture.

Method  Bacillus stains were isolated from the pond sediment and healthy carp (Carassius auratus) intestine. The strains were identified by the morphological, physiological and biochemical characteristics and 16S rRNA sequence analysis. The safety, high temperature tolerance, pH tolerance, antagonistic effects and enzyme production of the strains were studied.

Result  Two Bacillus strains were isolated and named B1 and B2. They were identified as B. subtilis by morphology, physiological and biochemical characteristics and 16S rRNA sequence analysis. The B1 and B2 strains had good safety, high temperature tolerance and strong tolerance of acid. They had good antibacterial activity against pathogenic Escherichia coli, Staphylococcus aureus, Aeromonas hydrophila and A. sobria in vitro, and had the ability to produce lipase, amylase, protease and cellulase.

Conclusion  Two B. subtilis strains were isolated, and both can be used as candidates for developing microecological agents for aquiculture.