On some basic theory aspects for robust-distributed parameter bioreactors

It is considered the model of the simplest case of a tubular bioreactor of the type plug-flow, where a single autocatalytic growth reaction takes place, with one limiting substrate and one biomass population. The model is discussed from the point of view of the so-called augmented validation that includes basic theory, definite sign of physical variables and inherent stability. The approach strongly relies on the association of a nonlinear second order ordinary differential equation that can be integrated in an elementary (classroom) way.