Fig. 1

Comparison of the maximal cell density and specific growth rate of strains evolved under the stress of different concentrations of inhibitors. E0 represents the starting strain E. coli LGE2 growing in LB media without inhibitors. r1–r4 of E1 represent the strains that were evolved by four-round transfers in the same concentration of inhibitor cocktail composed of 0.7 g/L acetic acid, 0.8 g/L furfural, and 0.6 g/L phenol. For E2, the inhibitor concentration was increased by 0.14 g/L acetic acid, 0.16 furfural g/L, and 0.12 g/L phenol compared to E1, and this is also the increment of E3 vs E2, E4 vs E3, E5 vs E4, and E6 vs E5. r6 represents the strains that were successively transferred by six rounds. Each strain used in the new transfer was the strain obtained by the last-round evolution. These strains were all cultured microaerobically within a maximum of 96 h at 37 °C until the cells stopped growing