Figure 2.

Experimental setup and metabolite measurements. Uptake and production were calculated as $\left(\left[C_{\mathrm{chemostat}}\right]-\left[C_{\mathrm{medium}}\right]\right)/X$, where C represents the metabolite concentration (mmol l⁻¹) and X the dry weight of the cells (g_DW l⁻¹). Fluxes are calculated by multiplication with the dilution rate (d=0.15 h⁻¹). (a) Experimental setup. The pH was shifted from 7.5 to 6.5 over the course of an hour. Samples were taken at the steady state at pH 7.5 (t₁), during the pH shift (t₂) at pH 7.0 after 30 min, as well as 80 min, 100 min, 120 min, 180 min, 240 min, and 21 h (t_3–8) after the initializing the pH shift. (b) Carbohydrate measurements. The measured uptake and production (given in $\mathrm{mmol}{\mathrm{g}}_{\mathrm{DW}}^{-1}$) are determined in continuous fermentation of the chemically defined medium. (c) Amino-acid measurements. The measured uptake and production (given in $\mathrm{mmol}{\mathrm{g}}_{\mathrm{DW}}^{-1}$) are determined in continuous fermentation of the chemically defined medium. Cit, citruline; Orn, ornithine. Chemostat 1 and 2 represent biological replicates. Metabolites with significant changes between the steady states are indicated by *P<0.05. The flux boundaries derived from the metabolite measurements are listed in Supplementary Table S5 (pH 7.5) and Supplementary Table S6 (pH 6.5).