Screening Of Media For Shaking Flask Fermentation Of Bacillus Thuringiensis

This study mainly concerns the screening of media for shaking flask fermentation of Bt WB7 by different experiment design and how to write a program for the algorithm.Media which was mainly composed of dextrose and peptone were screened with shake flask fermentation and orthogonal test. Results indicated that spore numbers were mainly influenced by dextrose and peptone. The interactions between dextrose and peptone also affected the production of spores. Among inorganic salts, the influence of MgSO4 7H2O is more noticeable than others. The most appropriate fermentative media is composed of dextrose 1%, peptone 1%, yeast extract paste 0.6%, KH2PO4 0.2%, FeSO4 7H2O 0.002%, ZnSO4 7H2O 0.005%, MnSO4 H2O 0.005% and MgSO4 7H2O 0.03%.The effects of cultivation media compositions including carbon source (dextrose), nitrogen source (peptone and yeast extract) and phosphorus source (KH2PO4) for the spore numbers were accessed by using quadratic-orthogonal-rotational-combinational test. A response-plane equation was formed as follows:y=20.84+2.7345x1+3.0179x2-0.0389x3+2.0825x1x2-1.25x1X3-0.415x2X3 -4.7568x12-3.2845x22-0.6334x32From this equation, it's easy to acquire the best combinational medium that include carbon source 1.27%, nitrogen source 2.144% and phosphorus source 0.122%.Bt WB7 was grown in culture media with different agricultural by-products as the main carbon and nitrogen sources. These products included corn starch, defatted soy flour, yeast powder, peptone and fish meal. Of this several products tested, corn starch and defatted soy flour were the most efficient substrates for Bt. It's not useful to put any fish meal to the media including defatted soy flour as nitrogen sources. It's important to have appropriate proportion between carbon and nitrogen sources.The optimization of fermentation medium of Bt WB7 was studied by using aorthogonal, rotational and combinative design of quadratic regression in the experiment. The mathematical model of reaction on the media was built up. The model was of high prediction and verified by the experimental data and it is reliable. The reaction regularity, relation between the two factors in the best combination of medium, the output and the mutual effect of different factors were discussed by use of the mathematic model. A good combinational medium was obtained as follows: corn starch 2.25%, defatted soy flour 2.6%, peptone 0.65% and fish meal 0.575%.