Institute of Biochemical Engineering, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, People's Republic of China.
School of Life Science, Yan'an University, Shanxi, 716000, People's Republic of China.
Microb Cell Fact. 2020 Nov 2;19(1):202. doi: 10.1186/s12934-020-01457-3.
In industrial fermentation, pH fluctuation resulted from microbial metabolism influences the strain performance and the final production. The common way to control pH is adding acid or alkali after probe detection, which is not a fine-tuned method and often leads to increased costs and complex downstream processing. Here, we constructed an intelligent pH-sensing and controlling genetic circuits called "Genetic pH Shooting (GPS)" to realize microbial self-regulation of pH.
In order to achieve the self-regulation of pH, GPS circuits consisting of pH-sensing promoters and acid-/alkali-producing genes were designed and constructed. Designed pH-sensing promoters in the GPS can respond to high or low pHs and generate acidic or alkaline substances, achieving endogenously self-responsive pH adjustments. Base shooting circuit (BSC) and acid shooting circuit (ASC) were constructed and enabled better cell growth under alkaline or acidic conditions, respectively. Furthermore, the genetic circuits including GPS, BSC and ASC were applied to lycopene production with a higher yield without an artificial pH regulation compared with the control under pH values ranging from 5.0 to 9.0. In scale-up fermentations, the lycopene titer in the engineered strain harboring GPS was increased by 137.3% and ammonia usage decreased by 35.6%.
The pH self-regulation achieved through the GPS circuits is helpful to construct intelligent microbial cell factories and reduce the production costs, which would be much useful in industrial applications.
在工业发酵中，微生物代谢引起的 pH 值波动会影响菌株性能和最终产量。常见的 pH 值控制方法是在探头检测后添加酸或碱，这种方法不是一种微调方法，往往会导致成本增加和下游处理复杂。在这里，我们构建了一种称为“遗传 pH 射击（GPS）”的智能 pH 感应和控制遗传回路，以实现微生物对 pH 的自我调节。
为了实现 pH 的自我调节，设计并构建了由 pH 感应启动子和产酸/碱基因组成的 GPS 回路。GPS 中的设计 pH 感应启动子可以响应高或低 pH 值并产生酸性或碱性物质，从而实现内源性自我响应的 pH 调节。构建了碱基射击回路（BSC）和酸射击回路（ASC），分别使细胞在碱性或酸性条件下更好地生长。此外，与 pH 值在 5.0 到 9.0 范围内的对照相比，GPS、BSC 和 ASC 遗传回路在番茄红素生产中的应用可实现无需人工 pH 调节的更高产量。在放大发酵中，携带 GPS 的工程菌株中的番茄红素产量增加了 137.3%，氨用量减少了 35.6%。
通过 GPS 回路实现的 pH 自我调节有助于构建智能微生物细胞工厂并降低生产成本，这在工业应用中非常有用。
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