Growth promoting activity of Penaeus indicus by secondary metabolite producing probiotic bacterium Bacillus subtilis isolated from the shrimp gut

In this study, 104 bacteria were isolated from the gut of Penaeus indicus. The morphologically different bacterial isolates were screened for probiotic properties. The strain D5 showed potent activity against various bacteria. The isolated strain Bacillus subtilis showed 17 mm zone of inhibition against Bacillus sp., 19 mm against Pseudomonas sp., 22 mm against Vibrio sp., and 22 mm against Micrococcus sp. The bacterial growth and bacterocin production in relation with incubation time was evaluated. Bacteriocin production was found to be high at the stationary phase and reduced considerably after fifth day. Bacterial growth and bacterocin production was maximum at pH 7.0 and optimum between pH 6.0 and 8.0. Incubation temperature is one of the important factors which significantly influences on the growth and production of bacteriocin. Bacterial growth and bacterocin production (17 ± 2 mm) were maximum at 30 °C. Glucose stimulated growth and bacterocin production (21 ± 3 mm). Among the supplemented nitrogen sources, glycine positively influenced on growth and metabolite production. In this study, bacteriocin supplemented diet enhanced the growth than control shrimp Bacteriocin was administered at various doses ranged between 10 and 50 mg/100 gm level. Shrimp length was 3.3 ± 0.13 cm and shrimp weight was 9.7 ± 0.12 g in 100 mg. The present finding revealed enhanced growth at high bacteriocin concentration. At 2 × 102 CFU/100 g probiotics in feed, the juvenile shrimp attained 16.8 ± 0.11 g after 40 days. The weight gain was 16.8 ± 0.11 CFU/100 g at 10 × 102 CFU/100 g probiotic concentration.