Kinetic Study of the Alcoholic Fermentation Process, in the Presence of Free and Immobilized Saccharomyces Cerevisiae Cells, at Different Initial Glucose Concentrations by Reversed Flow GC

Abstract

Reversed flow gas chromatography (RFGC) was applied for the kinetic study of the alcoholic fermentation processes conducted with cells of the alcohol-resistant and psychrophilic Saccharomyces cerevisiae AXAZ-1 yeast strain, either free or immobilized on wheat, barley and corn grains as well as on potato pieces. Repeated alcoholic fermentations with must of varying initial glucose concentrations were performed in order to estimate the catalytic efficiency of the biocatalysts used in the present study. With the RFGC method, the distinction of the duration of alcoholic fermentation phases was achieved, which may be correlated to the phases of AXAZ-1 cells growth cycle. The rate constants of ethanol production for each phase of the alcoholic fermentations, conducted with free and immobilized cells, were also determined with the aid of RFGC, confirming the predominance of the immobilized against free cells in the fermentation process. Comparing the supports used for immobilization, wheat and barley grains seemed to be more efficient than corn grains and potato pieces, as they provided a higher number of immobilized cells and rate constant values.