Abstract
Aim: The objective of the present work is to propose a model describing the evolution of the pure culture fermentation of two oenological yeasts: S. cerevisiae and T. delbrueckii.Methods and results: For both yeasts, pure culture fermentation was performed in a synthetic medium with different initial concentrations of yeast available nitrogen. The datasets obtained from those experiments were used to identify the parameters of the proposed model.Conclusions: The developed comprehensive model of wine-making fermentation is based on the partition of assimilated nitrogen between the constitutive and the storage compartments. It efficiently describes the evolution of S. cerevisiae and T. delbrueckii pure cultures. This mass-balance model provides a stoichiometric approach in biomass production, unlike nitrogen backboned models used in winemaking. Moreover, it gives an estimation of non-accessed data such as nitrogen partition between vacuole and cytosol during T. delbrueckii fermentation.Significance and impact of the study: The developed model is robust enough to precisely describe the fermentation evolution of two pure culture yeasts and therefore has future potential for modelling mixed culture fermentations of S. cerevisiae and T. delbrueckii.
Highlights
Wine fermentation is a widely studied process in which hexoses are mainly converted into ethanol and carbon dioxide. saccharomyces species are the yeasts most commonly used in winemaking, since they are tolerant to high ethanol levels (Pretorius, 2000)
This paper describes a comprehensive kinetic model in which yeast growth is based on assimilated nitrogen partition
The present comprehensive model of winemaking fermentation is based on the partition of assimilated nitrogen between the constitutive and the storage compartments and includes the following variables: yeast living cells, sugar, yeast assimilable nitrogen (YAN), ethanol, glycerol and stored nitrogen
Summary
Wine fermentation is a widely studied process in which hexoses are mainly converted into ethanol and carbon dioxide. saccharomyces species are the yeasts most commonly used in winemaking, since they are tolerant to high ethanol levels (Pretorius, 2000). Yeasts are living organisms whose activity requires nutrients to provide both the basic elements and energy required for various biochemical syntheses. Nitrogen is one such nutrient, being essential for metabolism and growth during alcoholic fermentation (Jiranek et al, 1995). During fermentation there is an intracellular amino acids concentration gradient between the cytosol and the more concentrated vacuoles (Wiemken and Dürr, 1974). This compartmentalisation contributes to the regulation of the activity of many enzymes involved in the metabolism (Sumrada and Cooper, 1982)
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