Characterization of<i>Bacillus</i>spp. isolated from intestine of<i>Labeo rohita</i>—Towards identifying novel probiotics for aquaculture

Abstract

The aim of the study was to evaluate the probiotic potential of two bacterial strains, Bacillus licheniformis COFCAU_BLP2 and B. subtilis COFCAU_BSP3, isolated from the intestine of a freshwater teleost fish rohu (Labeo rohita). The beneficial properties of the strains were evaluated using a range of in vitro tests, along with in vivo safety analysis. Among the two isolates, COFCAU_BSP3 showed effective antimicrobial response against several pathogenic bacteria and high tolerance to a wide range of pH (2–9), and bile salt concentration (2.5%–10%). Among the adhesion properties, COFCAU_BSP3 showed significantly higher (p < .05) in vitro adhesion to mucus, cell surface hydrophobicity and auto-aggregation capacity, compared to COFCAU_BLP2. The strain COFCAU_BSP3 was non-haemolytic, showed significantly higher (p < .05) antioxidative response than COFCAU_BLP2 and could produce extracellular enzymes. In vivo challenge study in rohu revealed the strain COFCAU_BSP3 as non-pathogenic. Overall, the in vitro assessments and safety study identified B. subtilis COFCAU_BSP3 as a potential probiotic from an autochthonous source and that it has the potential to be used in the aquaculture industry.