Ethanol effects on the overexpression of heterologous catalase in E. coli BL21 (DE3)

Escherichia coli (E. coli) is one of the most popular prokaryotic organisms used for producing recombinant proteins. Well characterized, convenient in genetic manipulation, low manufacturing cost, and amenability to high cell-density fermentation make E. coli expression system to be the most extensively used system in the industrial production of recombinant proteins. However, it is not uncommon that the overexpression of many recombinant proteins fail to reach in E. coli expression system due to misfolding proteins and forming inclusion bodies. A new strategy, ethanol treatment, to improve the expression of heterologous genes in E. coli was reported in recent studies. The detailed mechanism of this strategy is not clear to date.To understand the mechanisms of ethanol resistant or ethanol stress, a number of ethanol-response regulons such as ArcA and FNR along with numerous heat-stock genes have been identified using omics techniques and extensively studied . Many reports make effort to determine the phenotypic changes induced by ethanol stress which are necessary for ethanol tolerance. And several hypotheses have been suggested to explain the mechanisms by which ethanol activates the heat-stock response and oxidative stress of E. coli cells, the exact mechanism of this remains unclear. Increased expression of the recombinant proteins under ethanol treatment is unique and interesting. Understanding the exact molecular mechanism behind the increase in recombinant protein expression using ethanol treatment can be of enormous applications in future. So this study makes effort to uncover the mechanism of ethanol treatment for improving the heterologous gene expression in the recombinant E. coli strains. The comparative transcriptomic analysis of the recombinant has been performed under the condition of ethanol treatment and without ethanol treatment. And a comprehensive analysis of the transcriptomic data indicated that ethanol treatment not only lead to stress responses of the E. coli cells but also enhance the central metabolic of the E. coli cells. A lot of experiment results demonstrate that the enhanced central metabolic could be the main effect by ethanol treatment on the improving heterologous expression.