CULTIVATION OF ESCHERICHIA-COLI TO HIGH CELL DENSITIES IN A DIALYSIS REACTOR

High cell density cultivation of Escherichia coli on a glycerol-based mineral medium was studied. The cultivation was done in a dialysis rea ctor composed of two chambers. The inner chamber is formed and separat ed from an outer chamber by a membrane. Fresh medium was continuously exchanged with medium in the outer chamber so that both glycerol and o ther components of the medium were supplied to the inner chamber throu gh the membrane. Inhibitory substances diffused from the inner to the outer chamber and were subsequently removed with effluent from the out er chamber. Initially, mathematical models were used to describe the p rocess. The optimal cultivation parameters, such as the initial glycer ol concentrations in the two chambers, the desired transport rate acro ss the membrane, glycerol concentration in the feed/dialysing medium, and the time to start the medium exchange, were determined from prelim inary experiments and calculations. The actual cultivation results agr eed very well with the model predictions. A very high cell concentrati on of 174 g dry weight/I was obtained. This cell concentration is with in the range of the maximum theoretical concentration of E. coli in cu lture broth (160-200 g/1).