Semi-continuous ethanol production in bioreactor from whey with co-immobilized enzyme and yeast cells followed by pervaporative recovery of product – Kinetic model predictions considering glucose repression

Mathematical models for semi-continuous ethanolic fermentation in a whey medium employing co-immobilized Saccharomyces cerevisiae strain and β-d-galactosidase and for pervaporative product recovery from the resultant broth were developed. Kinetic parameters of biomass growth were estimated using the nonlinear least squares method on the basis of experimental data obtained from culture of suspended yeast cells grown in a mixture of glucose and galactose and during semi-continuous fermentation in a bioreactor in a whey medium with co-immobilized enzyme and yeast cells. Experimentally determined fluxes of ethanol and water from broth were applied for the estimation of kinetic constants of ethanol separation by pervaporation. The degree of sugar utilization and ethanol productivity in bioreactor as well as the time of ethanol separation needed to obtain the desired amount of product can be predicted using this model. The influence of selected operating parameters on the fermentation effectiveness was simulated based on the developed model.