Kinetic modeling of lactic acid production from batch submerged fermentation of cheese whey

A kinetic model for the production of lactic acid through batch submerged fermentation of cheese whey using Lactobacillus helveticus was developed. The model accounts for the effect of substrate limitation, substrate inhibition, lactic acid inhibition, maintenance energy and cell death on the cell growth, substrate utilization, and lactic acid production during the fermentation process. The model was evaluated using experimental data from Tango and Ghaly (1999). The predicted results obtained from the model compared well with experimental (R2 = 0.92-0.98). The model was also used to investigate the effect of the initial substrate concentration on the lag period, fermentation time, specific growth rate, and cell productivity during batch fermentation. The maximum specific growth rate ( µm), the saturation constant (KS), the substrate inhibition constant (KIS), and the lactic acid inhibition constant (KIP) were found to be 0.25 h–1, 0.9 g/L, 250.0 g/L, and 60.0 g/L, respectively. High initial lactose concentration in cheese whey reduced both the specific growth rate and substrate utilization rate due to the substrate inhibition phenomenon. The maximum lactic acid production occurred at about 100 g/L initial lactose concentration after 40 h of fermentation. The maximum lactic acid concentration above which Lactobacillus helveticus did not grow was found to be 80.0 g/L.