Figure 4. Modular optimization of ALA production by co-expression of hemA^s, hemL, hemD and hemF.

(a) Schematic representation of different combinations. The genes hemL (red arrow), hemA^s (green arrow), hemD (light blue arrow) and hemF (purple arrow) are assembled with the plasmids pACYCDuet-1 (red line), pCDFDuet-1 (blue line), pETDuet-1 (green line) and pRSFDuet-1 (orange line), respectively. (b) ALA production of recombinant strains with different gene combinations. (c) Batch fermentation of ALA by the engineered strain E. coli LA in a 3 l bioreactor. (d) Batch fermentation of ALA by the engineered strain LADF-6 in a 3 l bioreactor.