| The comparison of expression differences between direct fermentation of rapeseed meal and fermentation after bio-pretreatment of rapeseed meal to produce iturin A by Bacillus subtilis was studied. Then the effect of different carbon and nitrogen sources on the expression of iturin A was further investigated. The results showed that solid state fermentation of rapeseed meal by Aspergillus niger and Aspergillus oryzae with cell autolysis could greatly increase mass concentration of free amino nitrogen, and its initial mass concentrations were 8.7 times and 5.6 times as many as direct fermentation of rapeseed meal, respectively. The expression level of iturin A produced by direct fermentation of repeseed meal was significantly higher than that produced by fermentation of repeseed meal after Aspergillus niger and Aspergillus oryzaetreatments, and the highest mass concentration of iturin A reached 0.69 g/L,which was higher than the highest level with commercial peptone and yeast powder as the nitrogen source. Compared with other soluble carbon sources, wheat bran and corn bran which were low water soluble and release carbon sources were more beneficial to the expression of iturin A. When using wheat bran as carbon source, the highest mass concentration of iturin A reached 0.96 g/L, 1.6 times as many as that using glucose as carbon source. |
