Modeling high‐biomass‐density cell recycle fermentors

Since intrinsic models, which take into account cell volume fraction, follow from proper application of the law of conservation of mass to a multiphase system, the intrinsic modeling approach should be used whenever biomass occupies a significant volume fraction of the culture. A recent report 11 offers the first comparison of intrinsic and nonintrinsic model predictions to actual experimental data gathered from a high‐density yeast recycle fermentor. Here, the analysis of Jarzebski et al. 11 has been carried further to show that the improper nonintrinsic model predicts a steady‐state culture glucose concentration that differs from that given by the fundamentally correct intrinsic model by over 60% at the optimal, bleed stream flow rate. In addition, a revised formulation for an intrinsic ethanol mass balance is presented.