Butanol production by Clostridium pasteurianum NRRL B-598 in continuous culture compared to batch and fed-batch systems

•Comparison of batch, fed-batch and continuous ABE fermentation•Continuous long-term packed-bed fermentations for butanol production•Effect of process arrangement on fermentation efficiency

Butanol production by acetone–butanol–ethanol (ABE) fermentation is usually associated with Clostridium acetobutylicum. In this report, ABE fermentation using the little known, oxygen tolerant solventogenic strain, Clostridium pasteurianum NRRL B-598, in packed-bed continuous cultures is described and compared with suspended cells in continuous, batch and fed-batch processes. While the highest butanol and total ABE concentrations (8.3 and 12.3 g/L respectively), were obtained in fed-batch fermentation, the highest solvent yield and productivity (32% and 0.73 g/L/h), were achieved in packed-bed continuous fermentation at a dilution rate of 0.12 1/h. In these processes, the strain showed exceptional stability, as demonstrated not only by low deviations in process parameters in batch and fed-batch experiments but also long-term stability (over 700 h, or more than 35 bioreactor residence times) in continuous fermentations.