Batch fermentation and optimization of media for Bacillus thuringiensis.

The composition of No. II medium obtained with shaking cultivation contained three factors: nitrogen source, carbon source, and inorganic salts. The relationship between component factors (x(i)) of the media and spore numbers (y) of Bacillus thuringiensis (Bt) was demonstrated by the orthogonal-rotation-combination test. A response surface equation was formed as follows: y = 384 - 7.245x1 + 11.705x2 + 15.475x3 + 14.039x1(2) + 41.831x2(2) - 79.49x3(2) - 35.375x1x2 - 3.375x1x3 - 106.625x2x3. The results showed that this method is simple, practical, and rapid enough for selecting fermentation media for Bt. In addition, the whole course of batch fermentation was also investigated.