Segregated mathematical model for the fed-batch cultivation of a high-producing strain of Penicillium chrysogenum

A new segregated mathematical model for the penicillin fed-batch process is presented and applied to the growth of the pellet-forming, industrially used high-producing strain Penicillium chrysogenum S2. The model comprises two kinds of biomass (growing and producing, nongrowing and still producing), cell lysis, and complex medium as an important substrate for primary growth. In accordance with our experimental observation, product formation is not inhibited by glucose, but related to the growth rate. Maintenance metabolism is cell age-dependent. The model was verified with two sets of experimental data including exhaust gas measurements while keeping the estimated parameters almost constant. The presented model derived from that of Bajpai and Reuss (1980, 1981) does not describe our data properly. The particular influence of the pellet structure on the model is discussed. The necessity of new model assumptions (e.g., different kinds of biomass, non-constant maintenance coefficient) is explained by cell damage by lysis and shear forces, and the succeeding repair processes.