The dynamic behavior of a continuous culture of Saccharomyces cerevisiae subjected to a sudden increase in the diln. rate has been successfully modelled for anaerobic growth on glucose, and for aerobic growth on acetate, on ethanol, and on glucose. The catabolism responded by an immediate jump whereas biosynthesis did not. Thus catabolism was in excess to anabolism. The model considers the decoupling between biosynthesis and catabolism, both types of reactions being modelled by first-order kinetic expressions evolving towards maximal values. Yield parameters and maximal reaction rates were identified in steady state continuous cultures or during batch expts. Only the time const. of biosynthesis regeneration, Tx, and the time const. of catabolic capacity regeneration, tx, had to be identified during transient expts. In most expts. tx was around 3 h, and tcat varied between 2 and 2.5 h for the different metabs. investigated. [on SciFinder (R)]