Abstract An iterative method for the calculation of the characteristic kinetic parameters of biological transformation models (for free biomass) is proposed. The differential equations of the model are numerically integrated. The model coefficients are estimated by minimizing the sum of the squares of the deviations. The procedure is applied to original experimental data for alcohol production by S. cerevisiae under batch conditions, starting with different glucose concentrations from 25 up to 200 kg m −3. The alcoholic fermentation was chosen because of its complexity due to the inhibition effects of both the substrate and the product. The advantage of this procedure, in comparison with others, is that crude experimental data can be used without any manipulation; also, the model equations are employed without any type of simplification or linearization. The variation in the kinetic parameters with the initial glucose concentration are obtained for each batch run.