Experimental investigations of a robust control strategy applied to cultures of S. cerevisae

In this paper, two robust RST control schemes for the regulation of either the ethanol concentration or the dissolved oxygen concentration in cultures of S. cerevisae are presented and illustrated with various simulation and experimental results. Both controllers only require the prior knowledge about one stoichiometric coefficient and only one on-line measurement signal, making them easily implementable in an industrial environment. Disturbance rejection is ensured thanks to an on-line parameter adaptation procedure, which delivers as a side product an estimate of the growth rate that can be used for process monitoring purposes. The robustification of the controllers is achieved in a simple way, using the observer polynomial. Additional issues, such as the presence of a delay in the system response (as observed in real-life experiments) or non negligible sensor dynamics, are also addressed.