Effect of ammonium concentration on alcoholic fermentation kinetics by wine yeasts for high sugar content

摘要

Kinetics of alcoholic fermentation by Saccharomyces cerevisiae wine strains in a syntheticudmedium with high sugar content were established for different nitrogen initial content and areudpresented for 4 strains. The composition of the medium was close to grape must except thatudthe nitrogen source consisted mainly in ammonium and was varied from 120 to 290 mg N/Ludassimilable nitrogen. The overall nitrogen consumed was also estimated in order to determineudnitrogen requirement variability.udThe effect of assimilable nitrogen was in general greater on sugar consumption rates than onudgrowth and 3 kinds of effect on sugar consumption rates were observed: i) existence of anudoptimal initial nitrogen level for a maximal sugar consumption rate (inhibition if excess), ii)udno effect of nitrogen beyond the intermediary level (saturation), iii) sugar consumption rateudproportional to the initial nitrogen level (activation).udIn all cases, the amount of consumed nitrogen increased with its initial concentration and souddid the fructophilic capacity of the strains. The optimal requirement varied from 0.62 to 0.91udmg N per g of sugars according to the different strains. There was no general correlationudbetween the sugar assimilation rates and the nitrogen requirement.