Promoter engineering for high ectoine production in a lower saline medium by Halomonas hydrothermalis Y2
- 27 January 2021
- journal article
- research article
- Published by Springer Science and Business Media LLC in Biotechnology Letters
- Vol. 43 (4), 825-834
- https://doi.org/10.1007/s10529-021-03084-3
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.Keywords
Funding Information
- National Natural Science Foundations of China (31870094, 31670109)
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