Fig. 5.

Quantitative assay of intracellular reactive oxygen species in different engineered E. coli strains. a The levels of free radicals in all strains. b The effect of n-butanol on each strain. The optical density at 600 nm and fluorescence at 535 nm of the engineered E. coli strains were measured for cells cultured in PYG medium for different times (0 h, 20 h, 36 h, 60 h) at 37 °C. “TBHP” represents the positive control in which strains were treated with 0.5 M tert-butyl hydroperoxide, which is known a stressor, after inoculation to produce intracellular H₂O₂. Measurements were obtained from three replicate experiments