The bioreactor overflow device: An undesired selective separator in continuous cultures?

Abstract

Non-homogeneous cell suspensions in a continuous culture may result in a difference between the biomass concentrations in the culture vessel and in the effluent. This will have important consequences for values calculated for stoichiometric and kinetic coefficients. For the bacterium Acinetobacter calcoaceticus it was shown that the cells tend to be buoyant, and because of this, if the vessel overflow device is not designed properly, cells will be selectively removed from the reactor. Two different effluent removal devices were compared, only one of which functioned well. A mathematical model is proposed to explain the observations.