Los modelos matemáticos para investigar efecto de la temperatura sobre los parámetros cinéticos de la fermentación del etanol

Biochemical Engineering Journal 28 (2006) 36–43

Mathematical modeling to investigate temperature effect on kinetic parameters of ethanol fermentation
Muenduen Phisalaphong ∗ , Nuttapan Srirattana, Wiwut Tanthapanichakoon
Department of Chemical Engineering, Chulalongkorn University, Bangkok 10330, Thailand Received 21 June 2005; received in revised form 28 July 2005; accepted 27 August 2005Abstract A mathematical model was developed to describe the effects of temperature on the kinetic parameters of ethanol fermentation by the flocculating yeast, Saccharomyces cerevisiae M30, using cane molasses as the substrate. Three state variables, biomass, ethanol and the substrate and 12 kinetics parameters were used to describe the phenomenon. The kinetic parameters of the model weredetermined by using the least-square method. The influence of temperature and initial sugar concentration on cell activities was investigated and quantified. Arrhenius relationships between operating temperature and the maximum specific growth rate, specific production rate, specific death rate were then established. The activation energy for growth, ethanol production and death rate were 3.461 × 104 , 3.496× 104 and 1.777 × 105 kJ/kmol, respectively. Polynomial equations were established for the effects of temperature on the other kinetic parameters. A high temperature led to a decrease in the ethanol and cell yields but an increase in the inhibition effect of ethanol and sugar on cell growth and ethanol production. In addition, an inhibition effect of the initial sugar concentration on cell growthwas clearly observed. The adopted mathematical model could describe very well the dynamics of ethanol fermentation from the beginning up to the stationary phase. © 2005 Elsevier B.V. All rights reserved.
Keywords: Ethanol; Fermentation; Kinetics; Modeling; Temperature; Yeast

1. Introduction On account of limited global supply of oil, ethanol has reemerged as an alternative to, or extender for,petroleum-based liquid fuels. To effectively and efficiently operate the fermentation process, the kinetic characteristics of cell growth and ethanol production are required. During fermentation of Saccharomyces cerevisiae, the activities of the microorganisms closely respond to changes in the environmental conditions, which are accompanied by variations in the mass transfer around and themetabolic behavior of the microorganisms. To gain insight into the morphology-associated time-variant process dynamics, various kinetic models associated with key parameters for ethanol fermentation have been proposed [1–11]. One of the most important variables is temperature. Temperature effects on fermentation performance of selected yeast strains for ethanol productivity were reported [11–21]. In thework of Baranyl and Roberts [14], an arbitrary factor expressed as a function of the
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Corresponding author. Tel.: +66 2 218 6875; fax: +66 2 218 6877. E-mail address: muenduen.p@chula.ac.th (M. Phisalaphong).

environmental conditions including the temperature was introduced to describe the physiological state of the cells and the growth kinetic equation was multiplied by this factor. Theexponential increase of growth rate and productivity at high fermentation temperature were reported [15]. The deleterious effects of high temperature were considered to be due to the denaturation of ribosomes and enzymes and problems associated with the fluidity of membranes [16]. In order to describe the effect of temperature, an empirical linear polynomial model was proposed to illustrate theeffect of temperature and nutrient supplement on ethanol production rate [17]. The influence of temperature on the kinetics parameters of ethanol and xylitol fermentation by a Pachysolen tannophilus was investigated by S´ nchez et al. and the dependency of the maximum specific growth rate on the temperature was explained by the superposition of activation energies for cell growth and death [18]. The...