RECURSIVE ONLINE ESTIMATION OF THE SPECIFIC GROWTH-RATE FROM OFF-GAS ANALYSIS FOR THE ADAPTIVE-CONTROL OF FED-BATCH PROCESSES

Adaptive control provides several advantages for efficiently controlling the substrate level of complex biotechnological fed-batch processes. The main advantage is that no complicated structured model of the process and its kinetics must be derived, which itself is a time consuming and expensive task. Instead, a simple unstructured model with time varying parameters can be used for control purposes. The problem of accurately estimating these parameters is nontrivial. To improve the stability of the closed loop system, it is recommended to decouple the estimation of the parameters, especially of the specific growth rate mu(t) of the process, from the state estimation. This can be nicely accomplished by estimating mu(t) only from measurements of the partial pressure of oxygen in the exhaust gas of the fermenter. With this new method it is possible to estimate even rapidly changing parameters. This can not be achieved by any other method in such a simple way.