Fig. 5

Cellular engineering of E. coli for enhanced resistance to 5-ALA. A Generation and remove of ROS caused by intracellular and extracellular 5-ALA accumulation. B Intracellular and extracellular 5-ALA concentrations of strains overexpressing rhtA or eamA. C Yield and cell growth of strains overexpressing rhtA or eamA. Strains ALA12 and ALA13 represent strain ALA11 derivatives overexpressing rhtA and eamA gene, respectively. D Effects of reinforcing the antioxidant defense or oxidative damage repair systems on 5-ALA production. Control represents strain ALA13. The rest strains represent strain ALA13 derivatives overexpressing the gene of antioxidant defense and oxidative damage repair system, respectively. E Effects of simultaneously reinforcing the antioxidant defense and oxidative damage repair systems on 5-ALA production. All engineered strains contain the plasmid overexpressing the synthetic sRNAs targeting sucC, aceA, and hemB. Data are presented as mean values +/− SD (n = 3 independent experiments). **P < 0.01, Student’s two-tailed t-test