Response surface optimization of the cultivation conditions and medium composition a novel probiotic strain Bacillus pumilus STF26

Probiotics have been widely used in aquaculture as a controlling disease, enhancing immune responses, providing nutrients, and improving water quality. The use of Bacillus species as probiotics is expanding rapidly with increasing number of studies. Optimization of cultivation conditions and the medium composition for the improvement of novel potential probiotic strain Bacillus pumilus STF26 was performed by using response surface methodology (RSM). Factors optimized were temperature, pH and the concentrations of dextrose, yeast extract, KH₂PO₄ and MgSO₄.7H₂O. The optimum values are found as 30.9°C, 6.9, 20% (w/v), for temperature, pH and the concentrations of dextrose and 1.526% (w/v), 0.1% (w/v) and 0.5% (w/v), for yeast extract, KH₂PO₄ and MgSO₄.7H₂O, respectively. As a result, maximum biomass at optimum conditions was 10.42 g/L, which is nearly 2.5 times higher when compared to the one obtained by using Luria Broth medium at optimized temperature and pH values.