Abstract
The fermentation of cane sugar as substrate by Saccharomyces cerevisiae (enzyme) was critically investigated to obtain certain useful kinetic parameters and to determine the effect of temperature, pH, substrate and yeast (enzyme) concentration on the rate of fermentation. The results indicate that the rate of fermentation (measured as rate of production of CO2) increased in proportion with temperature (optimum 32°C - 36°C), pH (optimum 5.5) substrate (optimum 50 v/v%) and yeast concentration (optimum 3.5 - 4.5 w/v%) up to a limit and subsisted either as a plateau and/or, decreases as the case may be. This suggests that the reaction takes place in two steps. The kinetic parameters examined are maximum rate of reaction Vmax (2.0 × 102 M·min-1), catalytic constant, k2 (1.81 × 10-1 min-1), overall rate constant, k (1.53 × 101 min-1), order of initial reaction (approx. first order), dissociation constant of enzyme-substrate complex, ks (2.74 × 103), Michaelis constant, km (2.74 × 103 M), and the specific activity of enzyme on substrate concentration (1 × 10-1 w/v%). The result of this study showed that the equilibrium step involving k-1/k1 is the limiting step deciding the direction of reaction as well as the specific activity of the enzyme.
Highlights
The fermentation of biomass using suitable enzymes to obtain alcohol had in recent years attracted the attention of stake holders in the industrial sector
In an enzyme [E] catalyzed reaction involving a single substrate [S], the rate varies linearly with the substrate concentration at low concentration and at high concentration; the rate becomes independent of substrate concentration
The effect of temperature on fermentation kinetics was determined by keeping other factors such as substrate concentration, pH of the juice, yeast concentration, and fermentation time constant
Summary
The fermentation of biomass using suitable enzymes to obtain alcohol had in recent years attracted the attention of stake holders in the industrial sector. The catalytic activity is localized in certain amino acids residues in the protein enzyme which provide suitable sites for reaction in a lock and key system with substrate. In an enzyme [E] catalyzed reaction involving a single substrate [S], the rate varies linearly with the substrate concentration at low concentration (first order kinetics) and at high concentration; the rate becomes independent of substrate concentration (zeroth order kinetics). On this basis, the reaction scheme can be stated in terms of the mechanism. When k1 is very small, km is large indicating a weak binding between enzyme and substrate [10]
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