Process control in chemostat experiments

Abstract

An integral part of modern bioprocess engineering is on_line measurement and control of state variables. By this way, many of these variables can be made "culture parameters", i.e be kept constant. Only this opens the possibilities to provide access to the Civing cell e.g. - Study kinetics and metabolic control - control a bioprocess well enough to optimize the objective(s) of the process - obtain fundamental insights into normal and aberrant cell behaviour. However, the present state of the art with respect to on_line measurement is far from wha we need (Schigerl et al., 1987; van Brunt, 1987; Luong et al., 1988). We are in a satisfactorily comfortable situation considering physical variables because full advantage of the developments madeinthe field of chemical engineering can be taken. Considering chemical variables, we suffer most often from the fact that the analytical methods available are not suited for application within the sterile barrier of monoseptic bioprocesses. As a result, the measurements are no longer in situ. Moreover, many of those Sensors are not sufficiently selective for a single substance to be quantified in heterogeneous culture media. The consequence is the need for a pretreatment of samples and, hence, a considerable time delay and eventually loss of on_line characteristics and continuous availability of data. With respectto biological variables, the worstsituation is faced although these variables are the keys for optimal bio-process control.