Periodic Operation of Continuous Fermentations Subject to Periodic Variation of Dilution Rate

The possibility of improvement in performance of continuous bioprocesses by cycling of the dilution rate is analyzed using the pi-criterion. The analysis is concerned with bioprocesses the static behavior of which can be described completely in terms of one state variable, viz., concentration of the limiting substrate. Some widely applicable conditions for superiority of periodic control vis-a-vis the optimal stationary control and expressions for optimum cycling frequencies are derived analytically. The applications considered include fermentations for production of a variety of biochemicals.