SummaryThe inhibitory effect of ethanol is studied during alcoholic fermentation in strict anaerobiosis (initial dissolved oxygen stripped by gasing pure nitrogen). It is demonstrated that the ethanol produced during the batch fermentation is more inhibitory than the added ethanol (in the range of 0 to 72.6 ghter). By analogy with noncompetitive enzyme kinetic inhibition, the inhibition constant for added ethanol is 105.2 g/liter, and 3.8 g/liter for produced ethanol, which exhibits the same inhibition effects in all experiments where ethanol was added. The measurement of the intracellular alcohol concentration can explain the dual inhibitory effects of ethanol.

<p style="text-align: justify;">Dans un premier temps, les concepts cinétiques nécessaires à la compréhension et à la mise en œuvre de la fermentation alcoolique sont discutés.</p><p style="text-align: justify;">Dans un deuxième temps, à la lumière des résultats expérimentaux, nous montrons l'influence de la concentration initiale en sucre (glucose) sur les rendements en biomasse et en éthanol, sur la densité cellulaire et la vitesse moyenne de production d'éthanol. La concentration cellulaire est relativement faible (1,5 à 3 gl^-1) et ce, quelle que soit la concentration initiale en substrat.</p><p style="text-align: justify;">Après avoir discuté cette observation, nous montrons qu'il n'existe pas de phase exponentielle de croissance et que, lorsque la concentration initiale en sucre augmente, la fraction de temps de fermentation qui s'effectue à un taux de croissance supérieur à 10^-2 µm diminue très sensiblement.</p><p style="text-align: justify;">+++</p><p style="text-align: justify;">In that work, kinetic concepts concerning understanding and process of alcoholic fermentation are discussed. Refering to experimental results, it is shown that yield of biomass and of ethanol, cell density and mean speed of ethanol production are in connection with the initial level of glucose. Cell concentration is relatively low without any correlation with the initial concentration of substrate.</p><p style="text-align: justify;">It is shown that exponential growing phase does not exist; when increases the initial level of glucose decreases strongly the time of fermentation occuring with a level growing higher than 10^-2 µm.</p>

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