Thermodynamic Characterization of Saccharomyces cerevisiae Catalyzed Fermentation of Cane Sugar

Abstract

The rate of cane sugar fermentation with Saccharomyces cerevisiae was studied at temperatures between 30°C and 42°C in order to characterize the process using thermodynamic parameters such as enthalpy (ΔH*), activation energy (ΔE*), entropy (ΔS*), Gibbs free energy (ΔG*) and equilibrium constant (K). The parameters were evaluated on the basis of a consideration of Arrhenius, Eyring and Van’t Hoff’s equations. The results obtained are ΔH*, 91.85 KJ·mol-1; ΔE*, 91.85 KJ·mol-1, ΔS*, 2763 J·mol-1K-1; ΔG*, -762.09 KJ·mol-1, and equilibrium constant, K, 1.34 dm3·mol-1. These values were subsequently used to obtain by calculation the rate constant of the fermentation k, 1.43 × 1011 min-1, Arrhenius constant A (pre-exponential or frequency factor), 4.79 × 1026 min-1, orientation parameter, P, 4.48 × 1015 and the collision frequency Z, 1.07 × 1011 min-1. Finally the fermentation efficiency calculated on the basis of a complete combustion of glucose is 377.8%. The results showed that though the fermentation process is kinetically controlled, it is suggested that the positive impact of the feasible thermodynamics is limited by other process variables.