Fig. 4

a Comparison of d-lactate production by each promoter in flask-scale fermentations. The black, light gray, and dark gray indicate production of d-lactate after 4, 8, and 20 h, respectively. The error bars show the standard deviations from triplicate experiments. Production of d-lactate under control of strong synthetic nar promoter (b) and the wild-type nar promoter (c) in fed-batch fermentations. Black square, d-lactate; hollow circle, cell growth; hollow triangle, glucose; solid gray circle, DO level; red arrows, the time of DO downshift (induction)