Different Wines from Different Yeasts? “Saccharomyces cerevisiae Intraspecies Differentiation by Metabolomic Signature and Sensory Patterns in Wine”

Alcoholic fermentation is known to be a key stage in the winemaking process that directly impacts the composition and quality of the final product. Twelve wines were obtained from fermentations of Chardonnay must made with twelve different commercial wine yeast strains of Saccharomyces cerevisiae. In our study, FT-ICR-MS, GC-MS, and sensory analysis were combined with multivariate analysis. Ultra-high-resolution mass spectrometry (uHRMS) was able to highlight hundreds of metabolites specific to each strain from the same species, although they are characterized by the same technological performances. Furthermore, the significant involvement of nitrogen metabolism in this differentiation was considered. The modulation of primary metabolism was also noted at the volatilome and sensory levels. Sensory analysis allowed us to classify wines into three groups based on descriptors associated with white wine. Thirty-five of the volatile compounds analyzed, including esters, medium-chain fatty acids, superior alcohols, and terpenes discriminate and give details about differences between wines. Therefore, phenotypic differences within the same species revealed metabolic differences that resulted in the diversity of the volatile fraction that participates in the palette of the sensory pattern. This original combination of metabolomics with the volatilome and sensory approaches provides an integrative vision of the characteristics of a given strain. Metabolomics shine the new light on intraspecific discrimination in the Saccharomyces cerevisiae species.

RESEARCH OF THE RED GRAPES WHICH ARE GROWN UP IN THE SAMARA REGION FOR THE PRODUCTION OF THE WINEMAKING MATERIALS

Изучена возможность использования для производства винодельческой продукции винограда, выращиваемого в Самарской области. Исследованы два технических сорта красного винограда урожаев 2015–2016 гг. – Ливадийский черный и Мерло. Качество винограда соответствовало требованиям ГОСТ 31782–2012. Переработку винограда по красному способу вели в полупромышленных условиях. Брожение проводили на мезге с плавающей шапкой. Для сбраживания виноградной мезги использовали сухие французские винные дрожжи Sainte Georges S101. Температура бродящей мезги не превышала 28–30°С. Дображивание полученных виноматериалов и последующую их выдержку осуществляли при температуре (14 ± 1)°С. В результате получены сухие столовые виноматериалы. Показатели качества полученных виноматериалов удовлетворяют требованиям ГОСТ 32030–2013 по всем основным физико-химическим показателям качества и характеризуются достаточно высоким содержанием фенольных веществ. Виноматериалы имели насыщенный рубиновый цвет, характерные сортовые вкус и аромат. Полученные результаты подтверждают целесообразность проведения дальнейших исследований в области обоснования и разработки технологий получения винодельческой продукции в Самарском регионе. The possibility of use for production of wine-making production of the grapes which are grown up in the Samara region is studied. Two technical grades of red grapes of harvests of 2015–2016 Livadia black and Merlots are investigated. The quality of the grapes meets the requirements of GOST 31782–2012. Grapes processed by red method in semi-conditions. Fermentation was carried out on pulp with a floating cap. Dry wine yeast “Sainte Georges S101” (Fermentis, France) were used for fermentation of grape pulp. The temperature of the fermenting pulp did not exceed 28–30°C. After-fermentation of the received wine materials and the subsequent their endurance was carried out at a temperature of (14 ± 1)°C. Dry table wine materials are as a result received. The resulting wine materials meet the requirements of GOST 32030–2013 in all basic physical and chemical indicators of quality and characterized by a rather high content of phenolic substances. Wine materials had a rich ruby color, characteristic varietal taste and aroma. These results confirm the usefulness of further research in the field of study and the development of technologies for the production of wine production in the Samara region.

Biotechnological Approaches to Lowering the Ethanol Yield during Wine Fermentation

One of the most prominent consequences of global climate warming for the wine industry is a clear increase of the sugar content in grapes, and thus the alcohol level in wines. Among the several approaches to address this important issue, this review focuses on biotechnological solutions, mostly relying on the selection and improvement of wine yeast strains for reduced ethanol yields. Other possibilities are also presented. Researchers are resorting to both S. cerevisiae and alternative wine yeast species for the lowering of alcohol yields. In addition to the use of selected strains under more or less standard fermentation conditions, aerobic fermentation is increasingly being explored for this purpose. Genetic improvement is also playing a role in the development of biotechnological tools to counter the increase in the wine alcohol levels. The use of recombinant wine yeasts is restricted to research, but its contribution to the advancement of the field is still relevant. Furthermore, genetic improvement by non-GMO approaches is providing some interesting results, and will probably result in the development of commercial yeast strains with a lower alcohol yield in the near future. The optimization of fermentation processes using natural isolates is, anyway, the most probable source of advancement in the short term for the production of wines with lower alcohol contents.

Metabolic flux sampling predicts strain-dependent differences related to aroma production among commercial wine yeasts

Background Metabolomics coupled with genome-scale metabolic modeling approaches have been employed recently to quantitatively analyze the physiological states of various organisms, including Saccharomyces cerevisiae. Although yeast physiology in laboratory strains is well-studied, the metabolic states under industrially relevant scenarios such as winemaking are still not sufficiently understood, especially as there is considerable variation in metabolism between commercial strains. To study the potential causes of strain-dependent variation in the production of volatile compounds during enological conditions, random flux sampling and statistical methods were used, along with experimental extracellular metabolite flux data to characterize the differences in predicted intracellular metabolic states between strains. Results It was observed that four selected commercial wine yeast strains (Elixir, Opale, R2, and Uvaferm) produced variable amounts of key volatile organic compounds (VOCs). Principal component analysis was performed on extracellular metabolite data from the strains at three time points of cell cultivation (24, 58, and 144 h). Separation of the strains was observed at all three time points. Furthermore, Uvaferm at 24 h, for instance, was most associated with propanol and ethyl hexanoate. R2 was found to be associated with ethyl acetate and Opale could be associated with isobutanol while Elixir was most associated with phenylethanol and phenylethyl acetate. Constraint-based modeling (CBM) was employed using the latest genome-scale metabolic model of yeast (Yeast8) and random flux sampling was performed with experimentally derived fluxes at various stages of growth as constraints for the model. The flux sampling simulations allowed us to characterize intracellular metabolic flux states and illustrate the key parts of metabolism that likely determine the observed strain differences. Flux sampling determined that Uvaferm and Elixir are similar while R2 and Opale exhibited the highest degree of differences in the Ehrlich pathway and carbon metabolism, thereby causing strain-specific variation in VOC production. The model predictions also established the top 20 fluxes that relate to phenotypic strain variation (e.g. at 24 h). These fluxes indicated that Opale had a higher median flux for pyruvate decarboxylase reactions compared with the other strains. Conversely, R2 which was lower in all VOCs, had higher median fluxes going toward central metabolism. For Elixir and Uvaferm, the differences in metabolism were most evident in fluxes pertaining to transaminase and hexokinase associated reactions. The applied analysis of metabolic divergence unveiled strain-specific differences in yeast metabolism linked to fusel alcohol and ester production. Conclusions Overall, this approach proved useful in elucidating key reactions in amino acid, carbon, and glycerophospholipid metabolism which suggest genetic divergence in activity in metabolic subsystems among these wine strains related to the observed differences in VOC formation. The findings in this study could steer more focused research endeavors in developing or selecting optimal aroma-producing yeast stains for winemaking and other types of alcoholic fermentations.

Development of a New Assay for Measuring H2S Production during Alcoholic Fermentation: Application to the Evaluation of the Main Factors Impacting H2S Production by Three Saccharomyces cerevisiae Wine Strains

Hydrogen sulfide (H2S) is the main volatile sulfur compound produced by Saccharomyces cerevisiae during alcoholic fermentation and its overproduction leads to poor wine sensory profiles. Several factors modulate H2S production and winemakers and researchers require an easy quantitative tool to quantify their impact. In this work, we developed a new sensitive method for the evaluation of total H2S production during alcoholic fermentation using a metal trap and a fluorescent probe. With this method, we evaluated the combined impact of three major factors influencing sulfide production by wine yeast during alcoholic fermentation: assimilable nitrogen, sulfur dioxide and strain, using a full factorial experimental design. All three factors significantly impacted H2S production, with variations according to strains. This method enables large experimental designs for the better understanding of sulfide production by yeasts during fermentation.

Effect of Pure Culture of Yeast on the Characteristics of Wine Quality

Saperavi is one of the most distinguished varieties of wine among the grape varieties widely spread in Georgia. Along with the grapevine variety, the pure culture of yeast also plays a crucial role in producing high quality wine material, because wine is the product of the viability of yeast. All chemical transformations that take place during the alcoholic fermentation, as a result of which the grape juice is turned into a qualitatively new product, i.e. wine, are carried out by direct involvement of the ferment system of the yeast. In addition, in the process of viability, the yeast produces not only the primary products of fermentation (ethanol and carbon dioxide), but also a number of organic substances (secondary and by -products) that play a big role in forming the wine taste and aroma, as well as the antioxidants, which provide its sustainability, and some biologically active components. Therefore, selecting the pure culture of wine yeast and directing the alcoholic fermentation correctly with the use of it, will guarantee to obtain a high quality product.

THE INFLUENCE OF YEAST ON THE FORMATION OF VARIETAL CHARACTERISTICS OF APPLE NATURAL WINES

Fermentation is one of the most important stages in the production of fruit wines that determines the formation of their varietal characteristics. The purpose of the work is to investigate quality indices of variety fruit wines and establish interrelation between application of different types of yeast and organoleptic characteristics of wines obtained with their application. Influence of yeast race on apple wine sensory profiles, dynamics of apple wort fermentation, formation of secondary fermentation products determining organoleptic characteristics of apple wines has been studied. Yeast species Saccharomyces cerevisiae - Lalvin V-1116, Oenoferm C2, France CB and Saccharomyces byanus –Oenoferm Freddo, Fermivin PDM were used in this work. For the nutrition of wine yeast we chose Maxafarm’s nutrient mixture consisting of inactivated yeast, thiamine and ammonium salts. The significant influence of yeast races on the qualitative and quantitative composition of secondary fermentation products, the formation of varietal signs of fruit and berry natural wines was shown. It is recommended to use Fermivin PDM and Oenoferm Freddo yeast at a fermentation temperature from 22 °C to 26 °C and France CB yeast at a fermentation temperature from 16 °C to 18 °C for the production of apple natural wines for the formation of varietal characters.