Combining yield coefficients and exit-gas analysis for monitoring of the baker's yeast fed-batch fermentation

Baker's yeast is one of the micro-organisms that is studied most in literat ure. Therefore, a lot of knowledge on the biochemical pathways and correspo nding yield coefficients is available. This knowledge is combined with meas urements of oxygen and carbon dioxide in the exit-gas to determine the coef ficients appearing in the stoichiometric equations. In this manner, two mea surements are sufficient to yield on-line estimates for biomass, glucose, e thanol and the specific growth rate, and information about the (ill-defined ) nitrogen source NHq. This is not possible if the yield coefficients are n ot included in the estimation procedure. A sensitivity analysis illustrates that this estimation scheme is rather insensitive to uncertainties on the yield coefficients.