Effect of time delay in specific growth rate on the periodic operation of bioreactors with input multiplicities

The effect of time delay in specific growth rate (μ) on the periodic operation of bioreactors with input multiplicities is theoretically analyzed for productivity improvement. A periodic rectangular pulse is applied either in feed substrate concentration (Sf) or in dilution rate (D). Periodic operation under feed substrate concentration cycling gives improvement in productivity at lower value of -Sf of the two steady-state multiplicities of Sf only when the time delay in μ is larger. Whereas the larger value of -Sf gives improvement in average productivity for all values of time delay. Dilution rate (D) cycling gives an improvement in average productivity particularly for larger time delay in μ. This improvement in average productivity is obtained only at smaller value of dilution rate out of the two steady-state input multiplicities of D. © 1994 Springer-Verlag.