Fig. 2

Representative chromatogram of the supernatant from Escherichia coli strain DH1 fermentation analyzed with (a) the 50 mm guard column showing n-butanol (peak 1) elution, and (b) n-butanol concentration of the supernatant from E. coli strains DH1, DH1ΔacrB and BW25113 fermentations after 24 h, 48 h and 72 h analyzed with the 50 mm guard column, 300 mm column and 30 mm guard column. HPLC parameters: column temperature 55 °C, mobile phase 5 mM sulfuric acid, flow rate 1.0 mL/min (0.6 mL/min for 300 mm column), refractive index detection