Modelling and parameter estimation of ethanol production in a batch reactor by Saccharomyces cerevisiae

Abstract

In the present study was investigated the kinetic of batch fermentation with the purpose to describe the ethanol production by Saccharomyces cerevisiae. The fermentation was performed in a bioreactor under agitation of 175 rpm, temperature condition equal to 32 °C and pH at 3.0. In order to describe the behavior of microbial growth, product formation and substrate consumption, three mathematical models were proposed: a classic model based on mass balances for the batch reactor; a model based on microbial kinetics weighted by the maximum concentration of microorganism; and a model proposed in an attempt to predict the cellular decay behavior observed experimentally. The model that best fitted the experimental data was the classic model based on Monod kinetics. All models were implemented in FORTRAN and solved by applying the subroutine DASSL, in the end, the ESTIMA program was used to estimate the kinetic parameters of each model and the objective function adopted was least squares function. The estimated values of the parameters obtained for the best model were statistically significant and physically realistic and describe with good accuracy the experimental data: µ_max = 0.1155 h^-1; K₁ = 0.8984 h^-1; K = 0.4738 h^-1; Y_X/S = 0.0242; Y_X/P = 0.0451 e K_S = 24.3852 g.L^-1.