51. Application of Orthogonal Design to Optimize Fermentation Conditions of Bacillus amyloliquefaciens BI₂

Bacillus amyloliquefaciens BI₂, isolated from corn straw silage, exhibits to be antagonistic against many kinds of molds, especially Aspergillus flavus. In this work, optimization of the medium and culture conditions was studied by adopting the combining single-factor tests and an orthogonal experiment. On the study of the medium optimization, yeast powder, monosodium glutamate, sodium nitrate, and the proportion of starch and maltose were selected as four factors at three levels each. On the study of the optimizing culture conditions, medium volume, culture temperature, fermentation time, and inoculums size were used as four factors at three levels each. The results demonstrated that yeast powder and monosodium glutamate have significant effects on medium optimization; medium volume, culture temperature, and fermentation time give crucial influences on culture conditions, and the influences of the other factors are not remarkable. The optimized medium results shown by the interaction tests were as following: yeast powder 1.5 %, monosodium glutamate 2 %, sodium nitrate 0.8 %, starch 0.17 %, and maltose 0.33 %; the optimal culture conditions were displayed as following: medium volume 60 mL, culture temperature 30 °C, inoculums size 2 %, and fermentation time 36 h.