Mathematical modeling of kinetics and research on multiplicity of glycerol bioconversion to 1,3-propanediol

The excess kinetic models for substrate consumption and product formation were reexamined for the bioconversion of glycerol to 1,3 propanediol by Klebsiella pneumoniae . Whereas these kinetic models described the substrate consumption and the formation of 1,3 propanediol and acetic acid reasonably well, relative large deviations were observed for the formation of ethanol, especially at low substrate concentrations. A new term, i.e. the substrate concentration change ratio ( c S · D ) was found in this work to be useful for describing ethanol formation in continuous culture. The resulting kinetic models and parameters satisfactorily described both continuous and batch cultures of glycerol fermentation by Klebsiella pneumoniae under various conditions. The model also predicted the occurence of multiplicity in the bioprocess. Alteration of metabolic pathways associated with ethanol formation appeared to be the main reason causing multiplicity in a fermentation when transferring from substrate limiting to substrate sufficient conditions.