Sherry Wines: Worldwide Production, Chemical Composition and Screening Conception for Flor Yeasts

The manufacturing of sherry wines is a unique, carefully regulated process, from harvesting to quality control of the finished product, involving dynamic biological aging in a “criadera-solera” system or some other techniques. Specialized “flor” strains of the yeast Saccharomyces cerevisiae play the central role in the sherry manufacturing process. As a result, sherry wines have a characteristic and unique chemical composition that determines their organoleptic properties (such as color, odor, and taste) and distinguishes them from all other types of wine. The use of modern methods of genetics and biotechnology contributes to a deep understanding of the microbiology of sherry production and allows us to define a new methodology for breeding valuable flor strains. This review discusses the main sherry-producing regions and the chemical composition of sherry wines, as well as genetic, oenological, and other selective markers for flor strains that can be used for screening novel candidates that are promising for sherry production among environmental isolates.

Yeast race effect on the quality of base and young sparkling wines

Introduction. A disadvantage of the ancestral method (la méthode ancestrale), which is widely used in the production of sparkling wine, is that it is difficult to control fermentation. We aimed to identify the optimal yeast race for obtaining high-quality young sparkling wines with varietal aroma without yeast tones. Study objects and methods. Our study objects were base and young sparkling wines from Cabernet-Sauvignon prepared on various yeast races. Organic acids, sugars, and ethanol contents were determined by high performance liquid chromatography. Phenolic and coloring substances were measured by colorimetric method. Foaming properties were determined by air barbotage of a wine sample in a measuring cylinder; sparkling properties, by measuring the CO2 desorption rate; CO2 content, by volumetric method; viscosity, with a viscometer. Sensory evaluation was carried out according to standard methods. Results and discussion. The wines produced on the Odesskiy Chernyi-SD13 yeast race received the highest tasting scores of 7.82 and 9.05 points for base wine and young sparkling wines, respectively. They contained larger amounts of phenolic substances (1103 mg/dm3) and coloring agents (275 mg/dm3) and had higher color intensity (1.614). The panelists rated them highly on their complex varietal aroma and harmonious, velvety flavor, as well as their foaming and sparkling properties. This yeast race ensured intensive fermentation of sugars and a great amount of bound CO2 (up to 24.93%). Conclusion. The Odesskiy Chernyi-SD13 yeast race is optimal for making base and young sparkling wines by the bottle method. This technology can be used to produce high-quality sparkling wines in the crop year by large and small enterprises.

Comparative Genomics Supports That Brazilian Bioethanol Saccharomyces cerevisiae Comprise a Unified Group of Domesticated Strains Related to Cachaça Spirit Yeasts

Ethanol production from sugarcane is a key renewable fuel industry in Brazil. Major drivers of this alcoholic fermentation are Saccharomyces cerevisiae strains that originally were contaminants to the system and yet prevail in the industrial process. Here we present newly sequenced genomes (using Illumina short-read and PacBio long-read data) of two monosporic isolates (H3 and H4) of the S. cerevisiae PE-2, a predominant bioethanol strain in Brazil. The assembled genomes of H3 and H4, together with 42 draft genomes of sugarcane-fermenting (fuel ethanol plus cachaça) strains, were compared against those of the reference S288C and diverse S. cerevisiae. All genomes of bioethanol yeasts have amplified SNO2(3)/SNZ2(3) gene clusters for vitamin B1/B6 biosynthesis, and display ubiquitous presence of a particular family of SAM-dependent methyl transferases, rare in S. cerevisiae. Widespread amplifications of quinone oxidoreductases YCR102C/YLR460C/YNL134C, and the structural or punctual variations among aquaporins and components of the iron homeostasis system, likely represent adaptations to industrial fermentation. Interesting is the pervasive presence among the bioethanol/cachaça strains of a five-gene cluster (Region B) that is a known phylogenetic signature of European wine yeasts. Combining genomes of H3, H4, and 195 yeast strains, we comprehensively assessed whole-genome phylogeny of these taxa using an alignment-free approach. The 197-genome phylogeny substantiates that bioethanol yeasts are monophyletic and closely related to the cachaça and wine strains. Our results support the hypothesis that biofuel-producing yeasts in Brazil may have been co-opted from a pool of yeasts that were pre-adapted to alcoholic fermentation of sugarcane for the distillation of cachaça spirit, which historically is a much older industry than the large-scale fuel ethanol production.