BACKGROUND The SoxRS regulon of E. coli is activated in response to elevated dissolved oxygen concentration likely to protect the bacteria from possible oxygen damage. The soxS expression can be increased up to 16 fold, making it a possible candidate for recombinant protein expression. Compared with the existing induction approaches, oxygen induction is advantageous because it does not involve addition or depletion of growth factors or nutrients, addition of chemical inducers or temperature changes that can affect growth and metabolism of the producing bacteria. It also does not affect the composition of the growth medium simplifying the recovery and purification processes. RESULTS The soxS promoter was cloned into the commercial pGFPmut3.1 plasmid creating pAB49, an expression vector that can be induced by increasing oxygen concentration. The efficiency and the regulatory properties of the soxS promoter were characterized by measuring the GFP expression when the culture dissolved oxygen concentration was increased from 30% to 300% air saturation. The expression level of recombinant GFP was proportional to the oxygen concentration, demonstrating that pAB49 is a controllable expression vector. A possible harmful effect of elevated oxygen concentration on the recombinant product was found to be negligible by determining the protein-carbonyl content and its specific fluorescence. By performing high density growth in modified LB medium, the cells were induced by increasing the oxygen concentration. After 3 hours at 300% air saturation, GFP fluorescence reached 109000 FU (494 mg of GFP/L), representing 3.4% of total protein, and the cell concentration reached 29.1 g/L (DW). CONCLUSIONS Induction of recombinant protein expression by increasing the dissolved oxygen concentration was found to be a simple and efficient alternative expression strategy that excludes the use of chemical, nutrient or thermal inducers that have a potential negative effect on cell growth or the product recovery.

中文翻译：

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在大肠杆菌中通过新型氧诱导系统生产重组蛋白。

背景 大肠杆菌的 SoxRS 调节子响应升高的溶解氧浓度而被激活，这可能保护细菌免受可能的氧损伤。soxS 的表达最多可增加 16 倍，使其成为重组蛋白表达的可能候选者。与现有的诱导方法相比，氧气诱导的优势在于它不涉及添加或消耗生长因子或营养素、添加化学诱导剂或温度变化，这些都会影响产生菌的生长和代谢。它也不影响生长培养基的组成，从而简化了回收和纯化过程。结果将 soxS 启动子克隆到商业 pGFPmut3.1 质粒中，创建了 pAB49，这是一种可以通过增加氧气浓度来诱导的表达载体。当培养物溶解氧浓度从 30% 增加到 300% 空气饱和度时，通过测量 GFP 表达来表征 soxS 启动子的效率和调节特性。重组 GFP 的表达水平与氧浓度成正比，表明 pAB49 是一种可控的表达载体。通过测定蛋白质-羰基含量及其特定荧光，发现氧浓度升高对重组产物的可能有害影响可以忽略不计。通过在改良的 LB 培养基中进行高密度生长，通过增加氧浓度来诱导细胞。在 300% 空气饱和度下 3 小时后，GFP 荧光达到 109000 FU（494 mg GFP/L），占总蛋白的 3.4%，细胞浓度达到 29.1 g/L (DW)。