In comparison to the different fermentation modes for the production of acetone, butanol and ethanol
(ABE) researched to date, the continuous fermentation is the most economically favored. Continuous
fermentation with two or more reactor cascade is reported to be the most efficient as it results in a more
stable solvent production process. In this work, it is shown that a continuous (first-stage) reactor coupled
to a repeated fed-batch (second stage) is superior to batch and fed-batch fermentations, including
two-stage continuous fermentation. This is due to the efficient catalyst use, reported through the specific
product rate and rapid glucose consumption rate. High solvents are produced at 19.4 gABE l−1, with volumetric
productivities of 0.92 gbutanol l−1 h−1 and 1.47 gABE l−1 h−1. The bioreactor specific productivities of
0.62 and 0.39 g g−1
cdw h−1 obtained show a high catalyst activity. This new process mode has not been
reported before in the development of ABE fermentation and it shows great potential and superiority to
the existing fermentation methods.