Kinetic Study of the Fermentation of Soursop Juice Using Saccharomyces Cerevisiae with Effect of Succinic Acid
C Ogbebor, A C. Ogonegbu
The fermentation of soursop juice as substrates by Saccharomyces cerevisiae (yeast) was investigated to obtain certain useful kinetic parameters. These were achieved by the determination of the effects of temperature, yeast, pH, substrate and inhibitor on the rate of carbon (IV) oxide (CO2) production. The extent of inhibition was examined by the additio n of succinic acid. The results indicate that the rate of fermentation increased in proportion with temperature (optimum 36oC), substrate (optimum 50%v/v) and succinic acid (optimum 30%v/v) up to a limit and decreased. This suggests that the reaction takes place in two steps (equilibrium and decomposition steps). The kinetic parameters examined are: maximum velocity of reaction, V max for substrate, 2.58x102M1min-1 and succinic acid, 1.00x10 2M1min-1. Catalytic constant, k 2; for substrate, 8x10 - 2min-1 and succinic acid, 6.0x10 -2min-1. Overall rate constant k, for substrate, 1.79x10 2 and succinic acid, 1.09x102. The order of initial reaction is first order for substrate and the additive. The dissociation constants of enzyme -substrate complexes, k s are 1.64x102 and succinic acid, 2.40x10-1. The Michaelis constant, k m for the substrate, 1.64x10 2 M and succinic acid, 2.50x10 -1. The specific activity of enzyme for the substrate is 1x10 -1 and succinic acid, 2x10 -2. Finally, the type of inhibition was found to be uncompetitive from the extrapolated Lineweaver-Burk plots and the suggested inhibitor did not bring about marked decrease in the rate of fermentation as expected.