Effects of acetoin stress on cell physiological characteristics in the different engineered strains. (a) ROS generation. (b) Cell viability. (c) ATP production. (d) ΔΨm. Error bars represent mean values and standard deviations of three independent experiments (black square, C-pYX; white square, C-Fzo1; blue square, C-Dnm1) (*P < 0.05 vs. the group of strain C-pYX).