Metabolic engineering for improving ectoine production in Escherichia coli

Previously, we have developed an Escherichia coli strain MWZ003/pFT28- ectABC - EclysC* - aspDH - ppc3 in which the titer of ectoine reached 30.37 g/L with a yield of 0.13 g/g glucose after 36 h fed-batch fermentation. In this study, this strain was further modified to improve the production of ectoine. Genes pflB encoding the pyruvate formatelyase, poxB encoding the pyruvate oxidase, adhE encoding the alcohol dehydrogenase, and aroG encoding the 3-deoxy-7-phosphoheptulonate synthase were deleted from MWZ003, resulting in the strain MWL007. Comparing with the control MWZ003/pFT28- ectABC - EclysC* - aspDH - ppc3 , ectoine production in MWL007/pFT28- ectABC - EclysC* - aspDH - ppc3 increased 21% with a yield of 0.43 g/g glucose. The gene mscS encoding the small conductance mechanosensitive channel MscS was further deleted in MWL007, resulting in the strain MWL009. Comparing with the control MWZ003/pFT28- ectABC - EclysC* - aspDH - ppc3 , ectoine production in MWL009/pFT28- ectABC - EclysC* - aspDH - ppc3 increased 28% with a yield of 0.46 g/g glucose. After the fermentation conditions were optimized, ectoine production in MWL009/pFT28- ectABC - EclysC* - aspDH - ppc3 further increased and the yield reached 0.63 g/g glucose. After 60 h fed-batch fermentation, the titer of ectoine in MWL009/pFT28- ectABC - EclysC* - aspDH - ppc3 reached 34.27 g/L with the yield of 0.34 g/g glucose. These results indicate that ectoine production in MWL009/pFT28- ectABC - EclysC* - aspDH - ppc3 can be improved by accumulation of the key precursors.