Title : Production of recombinant Bacillus subtilis expressing L-gulonolactone oxidase and its efficacy on innate immune responses in Nile tilapia
In recent years, various probiotic strains have been applied in the aquaculture industry as acceptable strategies for prevention and treatment of aquatic animal diseases. However, conventional probiotic applications have limitations. Therefore, in this study, the recombinant probiotic B. subtilis expressing L-gulonolactone oxidase was constructed to provide a promising approach to stimulate an immune response in Nile tilapia. Three experimental diets, including 1.) basal diet as a control, 2.) basal diet supplemented with native B. subtilis and 3.) basal diet supplemented with recombinant B. subtilis expressing L-gulonolactone oxidase were fed to Nile tilapia for 30 days, and its efficacy on innate immune responses were evaluated. The results showed that total immunoglobulin and alternative complement 50 activity (ACH50) of fish fed with diets supplemented with native B. subtilis and recombinant B. subtilis expressing L-gulonolactone oxidase were significantly higher than those of the control (P<0.05) but had no significant effects on lysozyme activity. Therefore, our results suggest that feed supplemented with B. subtilis and recombinant B. subtilis expressing L-gulonolactone oxidase could promote health in Nile tiaplia. Further study should be explored their probiotic effects under pathogen challenge conditions.