Optimization of Culture Conditions for the Growth of Bacillus subtilis natto Utilizing Soybean Meal as Nitrogen Source

Cell suspension turbidity(optical density at 660 nm,OD660 nm) was measured using an automated growth curve analyzer to investigate the growth of Bacillus subtilis natto during incubation in a liquid culture medium composed of soybean meal as nitrogen source and glucose as carbon source.The optimal concentrations of soybean meal and glucose were found to be 50 g/L and 10 g/L,respectively.Using one-factor-at-a-time combined with orthogonal array design method,temperature,pH and time were identify as major factors that influence the growth of Bacillus subtilis natto.Further,Box-Behnken experimental design was used to optimize the main influencing factors.Bacillus subtilis natto achieved the highest biomass after 13 h of incubation at initial pH 6.16 and 35.5 ℃ in the presence of soybean meal treated by ultrasonic for 4.32 min,and the cell suspension turbidity was 1.635 under these conditions.