Abstract Glutamic acid, a very important amino acid, is industrially produced by fermentation in batch processes. Continuous processes are often more economic. After identification of the biological system we can show that a two-stage cascade yields higher productivities than a standard batch or a one-stage continuous process. A segregated model dynamically simulates variing age distributions very well. Using results from simulation and fermentation runs in parallel saves a lot of time for the optimization of our process.