In bioreactors, the measurement of variables that play a key role in the quality and productivity of
fermentations, is of major importance. However, their direct measurement is often expensive or even
impossible considering the current sensor technology. Therefore, on-line estimation of unmeasured
variables in bioreactors can be an interesting approach.
The objective of this work is to introduce an alternative solution for the state observation of
bioprocesses in cases where the kinetic model is unclear and the concentration of the influent
substrates is badly known, a situation that is common in many practical applications.
The high-cell density fed-batch fermentation of Escherichia coli is studied in terms of applicability of
a simple interval observer for the estimation of relevant variables of the process, when uncertainties of
the process inputs exist.
The simple interval observer is designed on the basis of the cooperativity properties of the observer
error dynamics (Rapaport and Dochain, 2005). Further assumptions are the knowledge of the (lower
and upper) bounds of the influent substrate concentration. Furthermore, an appropriate state
transformation and conditions that guarantee system cooperativity have been introduced for that
purpose.
The performance of the interval observer is illustrated through numerical simulation.Programa de Desenvolvimento Educativo para Portugal (PRODEP)