A ROBUST FED-BATCH FEEDING STRATEGY FOR OPTIMAL PARAMETER-ESTIMATION FOR BAKERS-YEAST PRODUCTION

Parameter identification of structured models is often a problem in bi otechnology, because the poor data situation and the number of unknown parameters only allow for inaccurate estimates. But often only a subs et of all kinetic parameters of the model are of interest for producti on purposes, e.g. for fed-batch cultivation. These parameters should b e estimated with a given accuracy. In addition, the experiments for in formation acquisition with respect to these parameters should be as si mple as possible and should consider some practical restrictions. In t his contribution a fed-batch feeding strategy is proposed to allow for an accurate estimation of yield and of critical growth rate of baker' s yeast. The feeding also allows for economic and stereotyped use of s taff and equipment and is therefore suitable for routine use in screen ing of strains and media. The overall pattern is similar to that one, usually used in production scale to minimize errors by limited model v alidity. After an initial phase for achieving a reproducible state thr ee different growth rates are adjusted to cover the range of possible critical growth rates. From biomass and ethanol measurements yield and critical growth rate can be estimated with an accuracy of about 2.1%. The fermentation pattern ends up with a constant feeding rate to simu late a limited oxygen transfer rate and to allow for an uptake of resi dual sugar and ethanol before a dough test can be carried out. Beside experimental results simulations and sensitivity analyses are shown.