Saccharomyces cerevisiae × Saccharomyces uvarum hybrids generated under different conditions share similar winemaking features.

Interspecific hybrids among species in the Saccharomyces genus are frequently detected in anthropic habitats and can also be obtained easily in the laboratory. This occurs because the most important genetic barriers among Saccharomyces species are post-zygotic. Depending on several factors, including the involved strains, the hybridization mechanism and stabilization conditions, hybrids that bear differential genomic constitutions, and hence phenotypic variability, can be obtained. In the present study, Saccharomyces cerevisiae × Saccharomyces uvarum hybrids were constructed using genetically and physiologically different S. uvarum parents at distinct temperatures (13 and 20°C). The effect of those variables on the main oenological features of the wines obtained with these hybrids was evaluated. Hybrids were successfully obtained in all cases. However, genetic stabilization based on successive fermentations in white wine at 13°C was significantly longer than that at 20°C. Our results demonstrated that, irrespective of the S. uvarum parent and temperature used for hybrid generation and stabilization, similar physicochemical and aromatic features were found in wines. The hybrids generated herein were characterized by low ethanol production, high glycerol synthesis and the capacity to grow at low temperature and to produce malic acid with particular aroma profiles. These features make these hybrids useful for the new winemaking industry within the climate change era frame. Copyright © 2017 John Wiley & Sons, Ltd.

Nonconventional yeasts and hybrids for low temperature handcrafted sparkling ciders elaboration in Patagonia.

Yeasts play a crucial role in transforming apple must into cider. While Saccharomyces cerevisiae (Sc) has been traditionally associated to cider fermentations worldwide, cryotolerant species such as Saccharomyces uvarum (Su) as well as natural S. cerevisiae × S. uvarum (Sc×Su) hybrids have also been detected in ciders fermented at low temperatures. This study aimed to evaluate the ability of two Patagonian cryotolerant yeast strains (Su and Se) and their interspecific hybrids with a Sc to conduct handcrafted apple must fermentations and a second fermentation process (champenoise method). The main chemical parameters and sensory quality of the resulting sparkling beverages was also analysed. Firstly, Sc×Se and Sc×Su hybrids were evaluated in their fermentative features at laboratory scale. Hybrids were compared with their respective parental species evidencing significant differences in the physicochemical and aromatic composition of the obtained base ciders. Both Su parental strain and the hybrid Sc×Se were selected for performing pilot scale fermentations (250 L) using natural (non-sterilized) apple juice at two different temperatures: 20 °C and 13 °C. Sc parental strain was also evaluated for comparative purposes. All base ciders obtained were then subjected to a second fermentation. A high implantation capacity of both Su and the hybrid was evidenced at the lowest evaluated temperature, while commercial Sc strain was not detected at the final fermentation stage, independently from the temperature. All sparkling ciders exhibited distinct physicochemical profiles. Ciders inoculated with commercial Sc (but effectively fermented with local Sc strains) allowed the development of malolactic fermentation (MLF) in processes carried out at both temperatures. Contrarily, no MLF was observed in ciders inoculated with either Su or the hybrid. Sparkling ciders fermented with Su displayed the highest concentrations of 2-phenylethanol and 2-phenylethyl acetate, regardless of the fermentation temperature. Conversely, ciders fermented with the hybrid at 20 °C exhibited the highest concentrations of ethyl octanoate and ethyl decanoate, contributing to floral and fruity notes in the beverage. Sensory analysis conducted with untrained individuals revealed a preference for sparkling ciders produced with the hybrid strain at both 20 °C and 13 °C. The cider fermented at 20 °C exhibited floral notes, sweetness, and a full body, while ciders fermented at 13 °C displayed moderate acidity and a well-balanced profile. Conversely, a trained panel described the cider fermented at 20 °C with Su as a fruity and acidic beverage, whereas the ciders fermented at 13 °C exhibited intense bitterness and acidity. This study highlights the potential of cryotolerant Saccharomyces species and hybrids in the development of new starter cultures for producing artisanal sparkling ciders with distinctive properties.

Evaluation of cryotolerant yeasts for the elaboration of a fermented pear beverage in Patagonia: Physicochemical and sensory attributes.

The production of pome fruits as pears and apples, as well as their derived industries, is of great economic importance in North Patagonia. The elaboration of fermented beverages as cider or perry has evidenced a substantial diversification during the last years, with the evaluation of different fruit varieties, yeast starters and technological changes. In this work, two cryotolerant yeasts belonging to the species Saccharomyces uvarum were evaluated at laboratory and pilot scale in sterile and no-sterile pear must. One of the strains was originally isolated from apple chicha (strain NPCC1314) and the other from apple cider (strain NPCC1420) in Patagonia. Both physicochemical and sensory features of the fermented products were evaluated. Both strains were able to successfully complete the fermentations, although strain NPCC1420 showed the better kinetic properties including a faster sugar consumption than the strain NPCC1314. Both strains showed excellent implantation capacity, but the fermented products showed different chemical profiles. The perry fermented with the strain NPCC1314 was characterized by better sensory attributes as assessed by trained panelists and a greater acceptance for untrained public than the same fermented with the strain NPCC1420. The two strains were able to consume sorbitol, both in pear must and in agar-plates supplemented with sorbitol as the sole carbon source. This ability is described for the first time in S. uvarum, at least for the two strains evaluated in this work.

Inheritance of winemaking stress factors tolerance in Saccharomyces uvarum/S. eubayanus × S. cerevisiae artificial hybrids.

Stress has been defined as any environmental factor that impairs the growth of a living organism. High concentrations of ethanol, sugars and SO2 as well as temperature variations occurring during winemaking processes are some recognized stress factors that yeasts must overcome in order to avoid stuck or sluggish fermentations. At least two of these factors -sugar and ethanol concentrations- are strongly influenced by the global warming, which become them a worry for the future years in the winemaking industry. One of the most interesting strategies to face this complex situation is the generation of hybrids possessing, in a single yeast strain, a broader range of stress factors tolerance than their parents. In the present study, we evaluated four artificial hybrids generated with S. cerevisiae, S. uvarum and S. eubayanus using a non-GMO-generating method, in their tolerance to a set of winemaking stress factors. Their capacity to overcome specific artificial winemaking situations associated with global warming was also analyzed. All four hybrids were able to grow in a wider temperature range (8-37 °C) than their parents. Hybrids showed intermediate tolerance to higher ethanol, sugar and sulphite concentrations than their parents. Additionally, the hybrids showed an excellent fermentative behaviour in musts containing high fructose concentrations at low temperature as well as under a condition mimicking a stuck fermentation.

Fermentative behaviour and competition capacity of cryotolerant Saccharomyces species in different nitrogen conditions.

The selection of yeasts with low nitrogen requirement is a current need in winemaking. In this work, we analysed nitrogen requirements of strains belonging to the cryotolerant species S. uvarum, S. eubayanus and S. kudriavzevii, in order to evaluate their potential for conducting the fermentation of low nitrogen content grape musts. Our result demonstrated that S. eubayanus is the species less influenced by the increasing nitrogen concentrations in both growth and fermentation conditions. Strains showing the best behaviours, S. eubayanus NPCC 1285 and S. uvarum NPCC 1317, were selected to be tested in mixed cultures with S. cerevisiae T73 at different temperatures (12 °C, 20 °C and 28 °C) in synthetic grape must with different nitrogen concentrations (60, 140 and 300 mg/L YAN). The cryotolerant strains dominated the fermentations carried out at 12 °C while S. cerevisiae prevailed at 28 °C independently from the nitrogen concentration. At intermediate temperature, 20 °C, S. eubayanus mono and mixed cultures showed the best fermentative behaviour especially with low and intermediate nitrogen concentration. In summary, cryotolerant Saccharomyces species, particularly S. eubayanus, could be interesting tools to avoid fermentations stucks caused by low nitrogen content in grape musts.

Polyamine catabolism is involved in response to salt stress in soybean hypocotyls.

The possible relationship between polyamine catabolism mediated by copper-containing amine oxidase and the elongation of soybean hypocotyls from plants exposed to NaCl has been studied. Salt treatment reduced values of all hypocotyl growth parameters. In vitro, copper-containing amine oxidase activity was up to 77-fold higher than that of polyamine oxidase. This enzyme preferred cadaverine over putrescine and it was active even under the saline condition. On the other hand, saline stress increased spermine and cadaverine levels, and the in vivo copper-containing amine oxidase activity in the elongation zone of hypocotyls. The last effect was negatively modulated by the addition of the copper-containing amine oxidase inhibitor N,N'-diaminoguanidine. In turn, plants treated with the inhibitor showed a significant reduction of reactive oxygen species in the elongation zone, even in the saline situation. In addition, plants grown in cadaverine-amended culture medium showed increased hypocotyl length either in saline or control conditions and this effect was also abolished by N,N'-diaminoguanidine. Taken together, our results suggest that the activity of the copper-containing amine oxidase may be partially contributing to hypocotyl growth under saline stress, through the production of hydrogen peroxide by polyamine catabolism and reinforce the importance of polyamine catabolism and hydrogen peroxide production in the induction of salt tolerance in plants.