Monday, April 19, 2010
12-31

Evaluation of mathematical models for the effects of initial substrate concentration on ethanol fermentation of cashew apple juice by Saccharomyces cerevisiae

Álvaro Daniel Teles Pinheiro1, Maria Valderez Ponte Rocha2, Gorete de Ribeiro Macedo3, and Luciana R. B. Gonçalves1. (1) Chemical Engineering, Universidade Federal do Ceará, Campus do Pici, Bloco 709, Fortaleza, Brazil, (2) Chemical Engineering, Universidade Federal Rural do Semi-Árido, BR 110 - Km 47 Bairro Pres. Costa e Silva, Mossoró, Brazil, (3) Chemical Engineering, Universidade Federal do Rio Grande do Norte, Av. Sen. Salgado Filho 3000, Natal, Brazil

One of the greatest challenges for society in the twenty-first century is to meet the growing demand for energy for transportation, heating, and industrial processes and to provide raw material for the industry in a sustainable way. Nearly all fuel ethanol is produced by fermentation of sucrose in Brazil or corn glucose in the USA. However, these raw material bases will not be sufficient to satisfy the international demand. Considering that the use of agro-industrial residues can contribute for the reduction of production costs, cashew apple appears as an alternative raw material for ethanol production. In this work, mathematical models for the effects of initial substrate concentration on ethanol fermentation of cashew apple juice by Saccharomyces cerevisiae at 30°C were proposed and their kinetic model parameters were estimated. Batch experimental observations at five initial concentration substrate (24.4, 41.3, 62.9, 87.7 and 103.1 g.L-1) were used to formulate the model discrimination problem. Glucose, fructose, ethanol and glycerol concentration were measured by HPLC. Parameter values were obtained by a technique of non-linear regression, using the free software SCILAB version 5.1. Subsequently, the mathematical models and estimated parameters (μmax, Xmax, Pmax, Yx/s and Yx/p, among others) adequacy was evaluated and the variances of model predictions were compared. The kinetic models optimized described satisfactorily the batch fermentation process as demonstrated by the experimental results.

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