A visible steady state starts after 50 h in both reactors, corresponding
to 5 volumetric transfers. The time course of the
fermentation in two-stage reactors shows a maximum ABE concentration
of 14.6 g l−1 with butanol and acetone concentrations
of 9.6 and 4.4 g l−1 respectively (Fig. 1a and b). Glucose consumption
rate of 1.920 gglucose g−1
cdw h−1 and products yields of
0.24 gABE g−1
glucose and 0.16 gbutanol g−1
glucose from the 60 g l−1 fed
were achieved. Second reactor was more stable with smaller products
oscillations, as compared to the first reactor. Butanol and
solvent concentrations of 3.9 and 6.2 g l−1 in the first reactor are
below the toxicity limit. The cells were exposed to toxic butanol,