3.3 Improving glutarate by acetate uptake pathway
The strain Bgl41464 tried to uptake acetate directly from the medium for furthermore enhancing glutarate titer. Before that, the natural acetate degradation way was explored individually. We firstly tested the growth of Bgl4146 under different acetate concentrations (Fig. S2). The acetate growth and degradation were measured in M9 medium (pH 7.0) supplemented with acetate as the only carbon source. But 3 g/L and 6 g/L acetate could be consumed completely about 48h and 96h, respectively. In order to grow better and accelerate the consumption of acetate, we cultivated Bgl41464 in the fermentation medium with and without glucose (Fig. 4A and 4B). In order to improve the content of acetyl-CoA, the competition route of acetic acid was destroyed by eliminating the ackA gene and the acetate synthesis pathway was destroyed by knockout of thepoxB gene for obtaining more acetyl-CoA. Because Zhu et alfound that a combination of the three manipulations (deletion ofackA , overexpression of acs , accBC anddtsR1 ) caused a 16.3-fold increasing in the intracellular malonyl-CoA level than that in wild-type E. coli (Zhu et al., 2014). Therefore, we explored the impact of the deletions of acetate synthesis pathway (ackA or poxB ) for glutarate production in E. coli(Fig. 4A and 4B). We found that the glutarate production with glucose fermentation was about three times than without glucose fermentation. And the glutarate production reached a maximum of 0.70 g/L under 6 g/L acetate with strain Bgl51464 (BL21(DE3) ΔarcA ΔldhAΔatoB ΔpflB ΔackA carrying pAD1, pAD4, pAD6 and pACC4).