Kinetics of alcoholic fermentation by Saccharomyces cerevisiae wine strains in a synthetic
medium with high sugar content were established for different nitrogen initial content and are
presented for 4 strains. The composition of the medium was close to grape must except that
the nitrogen source consisted mainly in ammonium and was varied from 120 to 290 mg N/L
assimilable nitrogen. The overall nitrogen consumed was also estimated in order to determine
nitrogen requirement variability.
The effect of assimilable nitrogen was in general greater on sugar consumption rates than on
growth and 3 kinds of effect on sugar consumption rates were observed: i) existence of an
optimal initial nitrogen level for a maximal sugar consumption rate (inhibition if excess), ii)
no effect of nitrogen beyond the intermediary level (saturation), iii) sugar consumption rate
proportional to the initial nitrogen level (activation).
In all cases, the amount of consumed nitrogen increased with its initial concentration and so
did the fructophilic capacity of the strains. The optimal requirement varied from 0.62 to 0.91
mg N per g of sugars according to the different strains. There was no general correlation
between the sugar assimilation rates and the nitrogen requirement
