Inducing hyperosmotic stress resistance in succinate-producing Escherichia coli by using the response regulator DR1558 from Deinococcus radiodurans

- DR1558, a response regulator, was used for organic acid production.
- DR1558 can improve growth performance and succinic acid production.
- DR1558 upregulates the genes involved in glucose utilization and succinic acid synthesis.
- DR1558 enhances the accumulation of intracellular ATP, trehalose, and betaine.

Bio-based succinate synthesis process suffers from low production efficiency, especially in the late stage of fermentation because of high osmotic stress. In this study, DR1558 (a response regulator in tow-component signal transduction systems) from Deinococcus radiodurans was overexpressed in Escherichia coli Suc260. High concentration glucose and NaCl impact experiment results showed that the recombinant strain (E. coli Suc270) displayed higher tolerance to osmotic stress. Fermentation in a 3-L fermenter showed that the dry cell weight, glucose consumption, and succinic acid titer of Suc270 were 2.06, 90.2, and 55.4 g/L, which is an increase of 1.50-, 1.38-, and 1.26-fold, respectively, compared to those of Suc260. Moreover, the lag phase was shortened by 10 h compared to that of the control strain Suc260. Real-time PCR results showed that DR1558 could enhance the expression level of the genes involved in glucose utilization, ATP synthesis, and osmoprotectant (glycine betaine, trehalose) synthesis pathways. Intracellular ATP and osmoprotectant content analysis further showed that Suc270 accumulated much more intracellular ATP, glycine betaine, and trehalose than Suc260. In conclusion, DR1558 could affect ATP metabolism and the synthesis of osmoprotectants and thus enhance the cell's tolerance against osmotic stress.

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