In the early stage of the fermentation, the bigger the inoculum sizes are, the faster the reducing sugar degrades; these data were showed in Fig. 2. After 36 h fermentation, the reducing sugar declined slowly in all situations, 72h later the reducing sugar dropped to 7.68g/L in the medium when inoculated 0.4 %, and at the same time it got the maximum reducing sugar using ratio in the system. But for the output of δ-endotoxin, the inoculum size arrived to 0.3%, the δ-endotoxin accumulated up to 952ug/ml, which increased by 52%, 8% and 28%, respectively, when the inoculum sizes were 0.1 %, 0.2% and 0.4%. That is to say, the inoculum size was not the more the better, the more