Abstract
Objectives
For the stress from fermenters, downstream processing equipment, and wastewater treatment to be alleviated, lowering salt-dependence in the ectoine synthesis process is of great significance in the moderately halotolerant Halomonas hydrothermalis Y2.
Results
In H. hydrothermalis Y2, the σ70- and σ38-controlled promoters of ectA are predicted to be involved in the osmotic regulation of ectoine synthesis. By substituting the ectA promoter with a promoter P265 that identified in the outer membrane pore protein E of H. hydrothermalis Y2, the salt dependence of ectoine synthesis was significantly decreased. In the 500-ml flask containing various NaCl contents, the engineered strain (p/Y2/△ectD/△doeA) showed a remarkably enhanced ability in ectoine synthesis, especially under lower saline stress. After a 36-h fed-batch fermentation in the 1-l fermenter, p/Y2/△ectD/△doeA synthesized 11.5 g ectoine l−1 in the presence of 60 g NaCl−1 l, with a high 0.32 g ectoine l−1 h−1 productivity, a specific productivity of 512.2 mg ectoine per g cell dry weight (CDW)−1, and an excretion ratio of 67 % ectoine.
Conclusions
As no impaired growth was observed in strain p/Y2/△ectD/△doeA while ectoine synthesis was increased, this promoter engineering strategy provides a practical protocol for lowering the salt-dependence of ectoine synthesis in this moderately halotolerant strain.
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This work was funded by the National Natural Science Foundations of China (Grant nos. 31870094 and 31670109).
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All authors contributed to the study conception and design. LS, SY and ZQ performed the experiments. YC and LS design the research. LS, ZQ, WW and DX contribute to data analysis. YC, SY, and LY wrote and revise the manuscript. All authors read and approved the manuscript.
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Li, S., Shang, Y., Zhao, Q. et al. Promoter engineering for high ectoine production in a lower saline medium by Halomonas hydrothermalis Y2. Biotechnol Lett 43, 825–834 (2021). https://doi.org/10.1007/s10529-021-03084-3
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DOI: https://doi.org/10.1007/s10529-021-03084-3