Residence time distribution and enhanced fermentation in continuous reaction processes

Continuous fermentations of whey giving ethanol or organic acids as reaction products is the subject of the investigations presented in this paper. The objective is to develop and optimize a tubular fermentation system with special emphasis on the engineering aspects. A tubular fermentor is, in contrast to conventional systems like stirred vessels, characterized by a well defined and narrow residence time distribution. Hence, process design and process control are very easy. In flow direction a gradient occurs in the concentration of the substrate and of the reaction product. Inhibition of the fermentation activity by the reaction product can therefore be restricted to a very low yet unavoidable level at the end of the fermentation tube. Effective mixing and controlled mass transfer are achieved in turbulent flow with a very low energy demand in comparison to other fermentation systems.