Fuzzy control approach to mixed culture cultivation for PHB production process - Nitrogen time profile synthesis

The present paper considers the control problems of the mixed culture system where sugars (glucose) were converted to lactate by the microorganism L. delbrueckii and then the lactate was converted to PHB (poly-beta-hydroxybutyrate) by the microorganism R. euthropha. The strategy to determine the optimal nitrogen concentration profile that maximizes the PHB production at the end of the process is discussed. Fuzzy rules based on experts' knowledge of the process and previous investigations are proposed. They are applied together with previously developed fuzzy approach that maintains the lactate concentration at its' optimal value by means of the dissolved oxygen concentration set point and the substrate (glucose) concentration feeding rate simultaneously. It is shown that the intelligent approach proposed here outperforms the classical control strategies applied before.