Fig. 4
Regulation of the PK expression of E. coli strains in shake-flask cultivation. a Growth curve and glucose consumption of wild-type E. coli BL21(DE3) and recombinant E. coli strains harboring CRISPRi system. b HPLC analysis of mixed standard and the final fermentation broth of E. coli strains. c Time course of aconitate production and the final concentration of aconitic acid in E. coli strains. d Relative changes of metabolites in CRISPRi strains (CCRISPRi) versus control strain (Ccontrol). PK: pyruvate kinase (EC 2.7.1.40), encoded by pykA and pykF. WT: wild-type E. coli BL21(DE3) without CRISPRi system; control: recombinant E. coli with non-targeting CRISPRi system; pykA1, pykA2 and pykA3: recombinant E. coli containing CRISPRi system targeting different regions of pykA gene; pykF1, pykF2 and pykF3: recombinant E. coli carrying CRISPRi system targeting various regions of pykF gene. Mean ± S.E. (n = 3). *P < 0.05; **P < 0.01