The present study uses a mathematical-empirical approach to estimate the cardinal growth temperature parameters (T min , the temperature below which growth is no longer observed; T opt , the temperature at which the max equals its optimal value; opt , the optimal value of max ; and T max , the temperature above which no growth occurs) of 27 yeast strains belonging to different Saccharomyces and non-Saccharomyces species. S. cerevisiae was the yeast best adapted to grow at high temperatures within the Saccharomyces genus, with the highest optimum (32.3°C) and maximum (45.4°C) growth temperatures. On the other hand, S. kudriavzevii and S. bayanus var. uvarum showed the lowest optimum (23.6 and 26.2°C) and maximum (36.8 and 38.4°C) growth temperatures, respectively, confirming that both species are more psychrophilic than S. cerevisiae. The remaining Saccharomyces species (S. paradoxus, S. mikatae, S. arboricolus, and S. cariocanus) showed intermediate responses. With respect to the minimum temperature which supported growth, this parameter ranged from 1.3 (S. cariocanus) to 4.3°C (S. kudriavzevii). We also tested whether these physiological traits were correlated with the phylogeny, which was accomplished by means of a statistical orthogram method. The analysis suggested that the most important shift in the adaptation to grow at higher temperatures occurred in the Saccharomyces genus after the divergence of the S. arboricolus, S. mikatae, S. cariocanus, S. paradoxus, and S. cerevisiae lineages from the S. kudriavzevii and S. bayanus var. uvarum lineages. Finally, our mathematical models suggest that temperature may also play an important role in the imposition of S. cerevisiae versus non-Saccharomyces species during wine fermentation.The estimation of the temperature range in which microorganisms are able to grow is very important for the food industry, to guarantee food safety or optimize fermentative conditions, for example, but also in ecological and taxonomic studies to classify and identify the different species of microorganisms. In this way, several works have shown the marked importance of temperature for the growth of industrial yeasts (1,4,22,24), as well as the influence of this environmental factor in determining the natural distribution of wild species (12,21,23,25). Specifically, there is an increasing interest in determining the influence of temperature in the adaptation of Saccharomyces species to both wild and fermentative environments (8,21,25).The Saccharomyces genus includes several species associated only with natural habitats (S. cariocanus, S. kudriavzevii, S. mikatae, S. paradoxus, and S. arboricolus) and others that are present in both fermentative and wild habitats (S. cerevisiae and S. bayanus). The ability of the latter to ferment a broad range of beverages (cider, beer, and wines) and foods (bread, vegetables, etc.) (19) has unconsciously favored their selection by humans for thousands of years. It is thought that temperature could play an important role in the imposition and presence ...

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In this study, we identified a total of 33 wine yeast species and strains using the restriction patterns generated from the region spanning the internal transcribed spacers (ITS 1 and 2) and the 5.8S rRNA gene. Polymerase chain reaction (PCR) products of this rDNA region showed a high length variation for the different species. The size of the PCR products and the restriction analyses with three restriction endonucleases (HinfI, CfoI, and HaeIII) yielded a specific restriction pattern for each species with the exception of the corresponding anamorph and teleomorph states, which presented identical patterns. This method was applied to analyze the diversity of wine yeast species during spontaneous wine fermentation.

Nitrogen deficiencies in grape musts are one of the main causes of stuck or sluggish wine fermentations. In the present study, we have supplemented nitrogen-deficient fermentations with a mixture of ammonium and amino acids at various stages throughout the alcoholic fermentation. The timing of the nitrogen additions influenced the biomass yield, the fermentation performance, the patterns of ammonium and amino acid consumption, and the production of secondary metabolites. These nitrogen additions induced a nitrogen-repressed situation in the cells, and this situation determined which nitrogen sources were selected. Glutamine and tryptophan were the main amino acids consumed in all the fermentations. Ammonium is the preferred nitrogen source for biomass production but was hardly consumed when it was added in the final stages of the fermentation. The higher ammonium consumption in some fermentations correlated with a greater synthesis of glycerol, acetate, and acetaldehyde but with a lower synthesis of higher alcohols.

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We carried out fermentations with several nitrogen sources in different concentrations and studied nitrogen regulation by following the transcriptional profile of the general amino-acid permease (GAP1) and the ammonium permeases (MEP1, MEP2, MEP3). In wine fermentations the cells evolve from a nitrogen-repressed situation at the beginning of the process to a nitrogen-derepressed situation as the nitrogen is consumed. These nitrogen-repressed/derepressed conditions determined the different patterns of ammonium and amino-acid consumption. Arginine and alanine were hardly used under the repressed conditions, while the uptake of branched-chain and aromatic amino acids increased.

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Mixed inoculation of non-Saccharomyces yeasts and S. cerevisiae are of interest for the wine industry for technological and sensory reasons. We have analysed how mixed inocula of the main non-Saccharomyces yeasts and S. cerevisiae affect fermentation performance, nitrogen consumption and volatile compound production in a natural Macabeo grape must. Sterile must was fermented in triplicates and under the following six conditions: 3 pure cultures of S. cerevisiae, Hanseniaspora uvarum and Candida zemplinina and the mixtures of H. uvarum:S. cerevisiae (90:10), C. zemplinina:S. cerevisiae (90:10) and H. uvarum:C. zemplinina:S. cerevisiae (45:45:10). The presence of non-Saccharomyces yeasts slowed down the fermentations and produced higher levels of glycerol and acetic acid. Only the pure H. uvarum fermentations were unable to finish. Mixed fermentations consumed more of the available amino acids and were more complex and thus better able to synthesize volatile compounds. However, the amount of acetic acid was well above the admissible levels and compromises the immediate application of mixed cultures.