Relationship of Bacillus Thuringiensis Fermentation Level and Dissolved Oxygen

Based the fermentation physiology study for Bacillus thuringiensis (B.t), The results show that the concentration of dissolved oxygen (DO) in the fermentation broth is the key factor affecting fermentation level in B.t fermentation process. In the experiments of 12 L glass fermentor, the fermentation level (number of living gemmae) increases through improving the condition of oxygen supply. For example, raising the agitation speed from 300 r/min to 600 r/min, the unmber of bacteria (NB) will be increased 47.1%. Enlarging the agitator diameter properly, NB will be increased 13.6%. When the speed control in the whole fermentation process is variable, NB is increased 36% in comparing with that of the constant speed control (CSC). Furthermore, the shaft Power assumption is saved 50% in comparing with that in the CSC at 600 r/min. In the amplified experiments of 20 m~3 fermentor, after adjusting the inner structure; DO is increased and NB is also increased 15.3% in comparing with that in the original structure.