Mathematical modeling to investigate temperature effect on kinetic parameters of ethanol fermentation

A mathematical model was developed to describe the effects of temperature on the kinetic parameters of ethanol fermentation by the flocculating yeast, Saccharomyces cerevisiae M30, using cane molasses as the substrate. Three state variables, biomass, ethanol and the substrate and 12 kinetics parameters were used to describe the phenomenon. The kinetic parameters of the model were determined by using the least-square method. The influence of temperature and initial sugar concentration on cell activities was investigated and quantified. Arrhenius relationships between operating temperature and the maximum specific growth rate, specific production rate, specific death rate were then established. The activation energy for growth, ethanol production and death rate were 3.461 × 104, 3.496 × 104 and 1.777 × 105 kJ/kmol, respectively. Polynomial equations were established for the effects of temperature on the other kinetic parameters. A high temperature led to a decrease in the ethanol and cell yields but an increase in the inhibition effect of ethanol and sugar on cell growth and ethanol production. In addition, an inhibition effect of the initial sugar concentration on cell growth was clearly observed. The adopted mathematical model could describe very well the dynamics of ethanol fermentation from the beginning up to the stationary phase.