Modelling of a continuous two-phase partitioning bioreactor for the degradation of xenobiotics

The possibility of operating a two-phase partitioning bioreactor for phenol degradation in continuous mode has been explored in this paper, using a me chanistic model for the bioreactor. Characteristics of continuous culture f ermentations with substrate inhibition were investigated using steady-state and dynamic simulations. The simulations confirmed that over certain range s of aqueous dilution rates, up to three steady states for the cell and sub strate concentrations could be obtained. These corresponded to stable and u nstable steady states, as well as washout conditions. The unstable nature o f the steady states was examined for two different operating regions repres enting extremes of solvent dilution rate and feed substrate concentration. Step decreases in feed substrate concentration, when operating at the unsta ble steady state, resulted in the system reaching a stable steady state, wh ile step increases in feed substrate concentration eventually resulted in t he system washing out. Dynamic simulations also revealed variations in the sensitivity of the continuous model to substrate concentrations, depending on the operating point. This variation indicates non-linearity in dynamic b ehaviour. (C) 2000 Elsevier Science Ltd. All rights reserved.