Figure 6

Construction of lignin-tolerant R. opacus strains. (A) Adaptive evolution of strain MITXM-61^L33 for improved lignin tolerance. The strain was grown in a defined medium containing 16 g L⁻¹ glucose supplemented with different concentrations of lignin (3.0 ~ 3.8 g L⁻¹) in a flask. Five milliliters of the culture were sequentially transferred into a flask containing 50 ml of the fresh medium after 3, 6, 10, and 15 days of cultivation. (B) Growth of evolved R. opacus strains in the presence of lignin. Strains MITXM-61^L53 (black circle), MITXM-61^L33 (black square), and MITXM-61 (black triangle) were grown in a defined medium containing 16 g L⁻¹ glucose supplemented with 3.5 g L⁻¹ lignin. Values and error bars represent the mean and the standard deviation of triplicate experiments.