Optimization of Sporulation Conditions for Bacillus subtilis BSNK-5

Bacillus subtilis spores have important biological applications; however, high spore-cell densities and sporulation efficiencies in fermentation is poorly reported. This study systematically analyzed the spore densities and formation efficiency of B. subtilis BSNK-5 in different culture substrates. A response surface regression equation was established based on the results of single factor and Box-Behnken experimental designs. The optimal medium formulation, as predicted from the equation, consisted of soluble starch at 3 g.L-1, soybean flour at 12 g.L-1, and MgSO 4 at 5 g.L-1. The spore yield reached 2.43 x 10(9) CFU.mL(-1), and the sporulation rate was 83.3%, which was nearly three times higher than before optimization using an optimized medium at 36 degrees C and 200 rpm for 60 h.