DYNAMIC SENSITIVITY OF A CHEMOSTAT FOR A MICROBIAL REACTION WITH SUBSTRATE AND PRODUCT INHIBITION

A general microbial reaction with inhibition by its substrate and prod uct has been analyzed for its time-varying sensitivities and the effec t of step disturbances in the dilution rate and/or the feed substrate concentration. In the first part of the study, the sensitivities of a continuous well-mixed bioreactor with respect to the dilution rate, th e feed substrate concentration, and the steady-state concentrations ha ve been computed and compared with the sensitivities in batch mode, fo r which only the initial condition is applicable. The results are rela ted to the physiological and hydrodynamic features of the reactor and show that continuous operation is less sensitive than batch operation; this enhances the benefits of the former. The second part of this pap er considers the deviations in time for the concentrations of the cell mass, substrate, and product when there are step disturbances in the inflow stream. The deviation trajectories are interpreted in terms of the metabolic and flow processes. Using the concept of relaxation time s, it is shown that the predicted results agree with reported data for gluconic acid production.