Increased mannoprotein content in wines produced by Saccharomyces kudriavzevii×Saccharomyces cerevisiae hybrids

Improved Phenolic Compositions and Sensory Attributes of Red Wines by Saccharomyces cerevisiae Mutant CM8 Overproducing Cell-Wall Mannoproteins

The objective of this study was to improve the quality attributes of red wines by Saccharomyces cerevisiae (BCRC 21685) mutant CM8 with overexpression of high-mannose mannoproteins, with respective to phenolic compositions, colorimetric parameters, and consumer sensory attributes. The CM8 was mutated by ethyl methane sulfonate and showed the ability of overproducing cell wall mannoproteins selected by killer-9 toxin-containing YPD plates. Kyoho grapes were used as raw materials. It is interesting to find that the cell wall mannoproteins isolated from CM8 mutant possessed a significantly higher mannose content in the polysaccharide fraction (81% w/w) than that did from parent strain (66% w/w). The red wines made of winter grapes and CM8 (CM8-WIN) showed significantly greater total tannins, flavonols, and anthocyanins levels, as well as higher color, higher flavor, and higher consumer preference than those by its SC counterpart (SC-WIN). The characteristics of the red wines studied were further elucidated by principal component analysis. Conclusively, using CM8 starter could effectively endow the red wine with high-quality attributes via the interactions of high-mannose mannoproteins with wine compounds.

Metschnikowia pulcherrima represses aerobic respiration in Saccharomyces cerevisiae suggesting a direct response to co-cultivation

The use of non-Saccharomyces species as starter cultures together with Saccharomyces cerevisiae is becoming a common practice in the oenological industry to produce wines that respond to new market demands. In this context, microbial interactions with these non-Saccharomyces species must be considered for a rational design of yeast starter combinations. Previously, transcriptional responses of S. cerevisiae to short-term co-cultivation with Torulaspora delbrueckii, Candida sake, or Hanseniaspora uvarum was compared. An activation of sugar consumption and glycolysis, membrane and cell wall biogenesis, and nitrogen utilization was observed, suggesting a metabolic boost of S. cerevisiae in response to competing yeasts. In the present study, the transcription profile of S. cerevisiae was analyzed after 3 h of cell contact with Metschnikowia pulcherrima. Results show an over-expression of the gluco-fermentative pathway much stronger than with the other species. Moreover, a great repression of the respiration pathway has been found in response to Metschnikowia. Our hypothesis is that there is a direct interaction stress response (DISR) between S. cerevisiae and the other yeast species that, under excess sugar conditions, induces transcription of the hexose transporters, triggering glucose flow to fermentation and inhibiting respiration, leading to an increase in both, metabolic flow and population dynamics.

Modulating Wine Pleasantness Throughout Wine-Yeast Co-Inoculation or Sequential Inoculation

Wine sensory experience includes flavor, aroma, color, and (for some) even acoustic traits, which impact consumer acceptance. The quality of the wine can be negatively impacted by the presence of off-flavors and aromas, or dubious colors, or sediments present in the bottle or glass, after pouring (coloring matter that precipitates or calcium bitartrate crystals). Flavor profiles of wines are the result of a vast number of variations in vineyard and winery production, including grape selection, winemaker’s knowledge and technique, and tools used to produce wines with a specific flavor. Wine color, besides being provided by the grape varieties, can also be manipulated during the winemaking. One of the most important “tools” for modulating flavor and color in wines is the choice of the yeasts. During alcoholic fermentation, the wine yeasts extract and metabolize compounds from the grape must by modifying grape-derived molecules, producing flavor-active compounds, and promoting the formation of stable pigments by the production and release of fermentative metabolites that affect the formation of vitisin A and B type pyranoanthocyanins. This review covers the role of Saccharomyces and non-Saccharomyces yeasts, as well as lactic acid bacteria, on the perceived flavor and color of wines and the choice that winemakers can make by choosing to perform co-inoculation or sequential inoculation, a choice that will help them to achieve the best performance in enhancing these wine sensory qualities, avoiding spoilage and the production of defective flavor or color compounds.

Mannoprotein Content and Volatile Molecule Profiles of Trebbiano Wines Obtained by Saccharomyces cerevisiae and Saccharomyces bayanus Strains

: The production of volatile compounds has become one of the major technological features for yeast selection. In fact, although the aromatic profile of the wine is the sum of varietal-, pre-, post-, and fermentative-aroma compound, yeasts affect the quality of the grape from maturation throughout fermentation, metabolizing sugars and other components into alcohols, esters, organic acids, and aldehydes. Among the new technological features, the production of mannoproteins has gained interest. From this perspective, the main aim of this work was to characterize 9 strains of Saccharomyces cerevisiae and 1 of Saccharomyces bayanus for their volatile profiles and the release of mannoproteins. The strains were inoculated in Trebbiano musts and incubated at 15 °C; at the end of fermentation the wines were evaluated by GC/MS/SPME for their volatile profiles and mannoprotein content by enzymatic assay. The strains were inoculated at level ranging between 4.9 and 6.3 log CFU/mL but only the strains L318 and 12233X6167 were able to reach values of 7.5 log CFU/mL. The aromatic profiles resulted in a strain-specific fingerprinting. According to the principal component analysis, the wines produced by the strains L288, L234, and L318 were characterized by the presence of propanoic acid, butanol, octanoic acid, and 3 methyl pentanol while the wine obtained by the strain 12233x35G2 was characterized by the presence of propanoic acid, butanol, octanoic acid and 3 methyl pentanol while the strain 12233x35G2 was characterized by the presence of decanoic acid ethyl ester, heptanoic acid ethyl ester, and acetic acid 2 phenetyl ester. Regarding mannoproteins, the highest concentration was achieved by strain12233x6167 (104 mg/L). The data allowed to select the strains endowed with the best fermentation performances in terms of aroma and mannoproteins release.

Pulsed electric fields accelerate release of mannoproteins from Saccharomyces cerevisiae during aging on the lees of Chardonnay wine

The potential of PEF for triggering autolysis of Saccharomyces cerevisiae and accelerating the release of mannoproteins during aging on the lees of Chardonnay wine was evaluated. Release of mannoproteins in Chardonnay wine increased drastically in samples containing PEF-treated (5 and 10 kV/cm, 75 μs) yeasts. No mannoprotein release was observed in the first seven days of aging on the lees in wine containing untreated yeast; however, after the same time interval, the concentration of those compounds increased by 40 and 60% in wines containing yeast treated by PEF at 5 and 10 kV/cm, respectively. After 30 days of incubation, the mannoprotein concentration in wines containing yeast treated under the most intense PEF conditions reached the maximum value. Control cells, on the other hand, required six months to reach that maximum level. Chromatic characteristics, total polyphenol index, total volatile acidity, pH, ethanol, and CIELAB parameters of the wine were not affected during aging on the lees with untreated and PEF-treated yeast. On the other hand, the capability of the mannoproteins released from yeast treated by PEF for decreasing wine turbidity, foaming, and interacting with tannins was similar to that of those released from untreated yeast; the differences observed were a consequence of the varying concentration of mannoproteins. The result obtained demonstrates that PEF permits the acceleration of the aging-on-lees step while avoiding or reducing the problems associated with it. To achieve this effect, intense treatment is not required. Therefore, wineries could process lees by using the most economical PEF devices on the market.

Microbial Resources and Enological Significance: Opportunities and Benefits

Among the innovative trends in the wine sector, the continuous exploration of enological properties associated with wine microbial resources represents a cornerstone driver of quality improvement. Since the advent of starter cultures technology, the attention has been focused on intraspecific biodiversity within the primary species responsible for alcoholic fermentation (Saccharomyces cerevisiae) and, subsequently, for the so-called ‘malolactic fermentation’ (Oenococcus oeni). However, in the last decade, a relevant number of studies proposed the enological exploitation of an increasing number of species (e.g., non-Saccharomyces yeasts) associated with spontaneous fermentation in wine. These new species/strains may provide technological solutions to specific problems and/or improve sensory characteristics, such as complexity, mouth-feel and flavors. This review offers an overview of the available information on the enological/protechnological significance of microbial resources associated with winemaking, summarizing the opportunities and the benefits associated with the enological exploitation of this microbial potential. We discuss proposed solutions to improve quality and safety of wines (e.g., alternative starter cultures, multistrains starter cultures) and future perspectives.