BACKGROUND Rapeseed cake (RSC), as the intermediate by-product of oil extraction from the seeds of Brassica napus, can be converted into rapeseed meal (RSM) by solvent extraction to remove oil. However, compared with RSM, RSC has been rarely used as a raw material for microbial fermentation, although both RSC and RSM are mainly composed of proteins, carbohydrates and minerals. In this study, we investigated the feasibility of using untreated low-cost RSC as nitrogen source to produce the valuable cyclic lipopeptide antibiotic iturin A using Bacillus amyloliquefaciens CX-20 in submerged fermentation. Especially, the effect of oil in RSC on iturin A production and the possibility of using lipases to improve the iturin A production were analyzed in batch fermentation. RESULTS The maximum production of iturin A was 0.82 g/L at the optimal initial RSC and glucose concentrations of 90 and 60 g/L, respectively. When RSC was substituted with RSM as nitrogen source based on equal protein content, the final concentration of iturin A was improved to 0.95 g/L. The production of iturin A was further increased by the addition of different lipase concentrations from 0.1 to 5 U/mL into the RSC medium for simultaneous hydrolysis and fermentation. At the optimal lipase concentration of 0.5 U/mL, the maximal production of iturin A reached 1.14 g/L, which was 38.15% higher than that without any lipase supplement. Although rapeseed oil and lipase were firstly shown to have negative effects on iturin A production, and the effect would be greater if the concentration of either was increased, their respective negative effects were reduced when used together. CONCLUSIONS Appropriate relative concentrations of lipase and rapeseed oil were demonstrated to support optimal iturin A production. And simultaneous hydrolysis with lipase and fermentation was an effective way to produce iturin A from RSC using B. amyloliquefaciens CX-20.

中文翻译：

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同时用脂肪酶水解和油菜饼发酵，以生产解淀粉芽孢杆菌CX-20的iturinA。

背景技术菜籽饼（RSC）作为从甘蓝型油菜种子中提取油的中间副产物，可以通过溶剂提取除去油而转化为菜籽粕（RSM）。但是，与RSM相比，RSC很少用作微生物发酵的原料，尽管RSC和RSM均主要由蛋白质，碳水化合物和矿物质组成。在这项研究中，我们调查了使用解淀粉芽孢杆菌CX-20在水下发酵中使用未经处理的低成本RSC作为氮源生产有价值的环状脂肽抗生素iturin A的可行性。尤其是，在分批发酵中分析了RSC中的油对iturin A产量的影响以及使用脂肪酶改善iturin A产量的可能性。结果iturin A的最大产量为0。在最佳初始RSC和葡萄糖浓度分别为90和60 g / L时为82 g / L。当基于相等的蛋白质含量将RSC替换为RSM作为氮源时，iturin A的最终浓度提高到0.95 g / L。通过在RSC培养基中添加从0.1到5 U / mL的不同脂肪酶浓度，可以同时水解和发酵，从而进一步增加iturin A的产量。在0.5 U / mL的最佳脂肪酶浓度下，iturin A的最大产量达到1.14 g / L，这比不添加任何脂肪酶时的产量高38.15％。尽管首先显示了菜籽油和脂肪酶对iturin A的产生具有负面影响，但如果增加两者的浓度，其效果会更大，但同时使用时，它们各自的负面影响会减小。结论证明了适当的相对浓度的脂肪酶和菜籽油可支持最佳的iturin A生产。脂肪酶同时水解和发酵是使用解淀粉芽孢杆菌CX-20从RSC中生产出尿囊素A的有效方法。