Background: Auto-induction is a convenient way to produce recombinant proteins without inducer addition using lac operon-controlled Escherichia coli expression systems. Auto-induction can occur unintentionally using a complex culture medium prepared by mixing culture substrates. The differences in culture substrates sometimes lead to variations in the induction level.

Objectives: In this study, we investigated the feasibility of using glucose and lactose as boosters of auto-induction with a complex culture medium.

Methods: First, auto-induction levels were assessed by quantifying recombinant GFPuv expression under the control of the T7 lac promoter. Effectiveness of the additive-containing medium was examined using ovine angiotensinogen (tac promoter-based expression) and Thermus thermophilus manganese-catalase (T7 lac promoter-based expression).

Results: Auto-induced GFPuv expression was observed with the enzymatic protein digest Polypepton, but not with another digest tryptone. Regardless of the type of protein digest, supplementing Terrific Broth medium with glucose (at a final concentration of 2.9 g/L) and lactose (at a final concentration of 7.6 g/L) was successful in obtaining an induction level similar to that achieved with a commercially available auto-induction medium. The two recombinant proteins were produced in milligram quantity of purified protein per liter of culture.

Conclusion: The medium composition shown in this study would be practically useful for attaining reliable auto-induction for E. coli-based recombinant protein production.

背景：自诱导是一种使用 lac 操纵子控制的大肠杆菌表达系统无需添加诱导物即可产生重组蛋白的便捷方法。使用通过混合培养基质制备的复杂培养基可能会无意中发生自诱导。培养基质的差异有时会导致诱导水平的变化。

目的：在这项研究中，我们研究了使用葡萄糖和乳糖作为复杂培养基自诱导增强剂的可行性。

方法：首先，通过量化 T7 lac 启动子控制下的重组 GFPuv 表达来评估自诱导水平。使用绵羊血管紧张素原（基于 tac 启动子的表达）和嗜热栖热菌锰过氧化氢酶（基于 T7 lac 启动子的表达）检查了含有添加剂的培养基的有效性。

结果：用酶促蛋白质消化的多肽观察到自诱导的 GFPuv 表达，但用另一种消化的胰蛋白胨则没有观察到。无论蛋白质消化的类型如何，在 Terrific Broth 培养基中添加葡萄糖（终浓度为 2.9 g/L）和乳糖（终浓度为 7.6 g/L）都成功获得了与使用市售的自动感应介质。这两种重组蛋白的产量为每升培养物毫克量的纯化蛋白。

结论：本研究中显示的培养基成分对于实现基于大肠杆菌的重组蛋白生产的可靠自诱导具有实际用途。