KINETICS OF BATCH-PRODUCTION OF ETHANOL FROM CHEESE WHEY

A kinetic model for ethanol fermentation was developed. The model accounted for substrate limitation, substrate inhibition, ethanol inhibition and cell death and performed satisfactorily for predicting the transient responses of cell growth, ethanol production and substrate utilization during the batch fermentation process of cheese whey (R2 = 0.96 to 0.99). The maximum specific growth rate (mu(m)), the saturation constant (K(s)), the ethanol inhibition constant and the substrate inhibition constant were found to be 0.051 h-1, 1.9 g/l, 20.65 g/l and 112.51 g/l, respectively. The maximum ethanol concentration above which Candida pseudotropicalis does not grow was found to be 100 g/l. The maximum ethanol production occurred at about 150 g/l initial substrate concentration after about 62 h. High initial substrate concentrations reduced both the specific growth rate and the substrate utilization rate due to the substrate inhibition phenomenon.