A mathematical model has been developed by performing a non-linear regression analysis to simulate the fermentation process of glucose to lactic acid by considering the product-inhibition situation and substrate requirement for cell maintenance. To account for such an effect a toxic power (n) and a cell-maintenance factor (m) have been incorporated into the model. In the present study the order of inhibition was calculated to be 0.88. Moreover, a small value for the cell maintenance factor (m) indicates that the effect of this parameter on the lactic acid fermentation is not appreciable and hence can be neglected.