Improvement in the bioreactor specific productivity by coupling continuous reactor with repeated fed-batch reactor for acetone–butanol–ethanol production

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−1cdw 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.

► We investigate the two-stage fermentation where a continuous reactor is coupled with a repeated fed-batch reactor.
► It is found that this mode of fermentation results in high production solvent and specific productivity and better, effective catalyst usage.
► This mode of fermentation is superior to the classic two-stage continuous fermentation.