Performance of continuous tower loop bioreactors—II model calculations for substrate limited growth

Abstract The behavior of tower and tower loop reactors is described by the CSTR-PFR and PFR loop combination as well as by the one-dimensional dispersion model with a loop assuming negligible residence time of the cells in the loop. In tower reactors, an optimum intensity of longitudinal dispersion, Bo opt , exists at which the substrate conversion has its maximum. Conditions are determined at which, in tower loop reactors with no cells in feed, stable steady states exist. When the intensity of longitudinal dispersion in tower loop reactors is less than optimum ( Bo > Bo opt ) an optimum recirculation ratio, γ opt′ exists at which the substrate conversion is higher than at γ = 0 (in tower reactors without a loop) and at Bo opt . Liquid recycling not only prevents the washout of the cells at high Bo numbers but also improves substrate conversion considerably and yields maximum conversion at γ opt .