A RecombinantSaccharomyces cerevisiaeStrain Overproducing Mannoproteins Stabilizes Wine against Protein Haze

Abstract

Stabilization against protein haze was one of the first positive properties attributed to yeast mannoproteins in winemaking. In previous work we demonstrated that deletion of KNR4 leads to increased mannoprotein release in laboratory Saccharomyces cerevisiae strains. We have now constructed strains with KNR4 deleted in two different industrial wine yeast backgrounds. This required replacement of two and three alleles of KNR4 for the EC1118 and T73-4 backgrounds, respectively, and the use of three different selection markers for yeast genetic transformation. The actual effect of the genetic modification was dependent on both the genetic background and the culture conditions. The fermentation performance of T73-4 derivatives was clearly impaired, and these derivatives did not contribute to the protein stability of the wine, even though they showed increased mannoprotein release in vitro. In contrast, the EC1118 derivative with both alleles of KNR4 deleted released increased amounts of mannoproteins both in vitro and during wine fermentation assays, and the resulting wines were consistently less susceptible to protein haze. The fermentation performance of this strain was slightly impaired, but only with must with a very high sugar content. These results pave the way for the development of new commercial strains with the potential to improve several mannoprotein-related quality and technological parameters of wine.During the alcoholic fermentation of grape must, Saccharomyces cerevisiae ferments sugars to ethanol and other metabolites, such as glycerol, acetate, succinate, pyruvate, and several esters, all of which contribute to the sensorial properties of wine. In addition, yeast cells release cell constituents, such as proteins or polysaccharides, which also contribute to the quality of wine (13). Macromolecules derived from the yeast cell wall, particularly mannoproteins, have attracted much attention in the winemaking world for the past 15 years due to their reported contribution to wine quality and chemical stability (5). Chemical stabilization and, more specifically, protection against protein haze in white wines were some of the first enological properties described for mannoproteins. In some white wines, grape proteins aggregate and precipitate due to high temperatures or long storage time. The haziness may be perceived as spoilage by the consumer (49). Wines aged with yeast lees have lower haze potential than wines aged without lees, and this is due to the protective effect of the mannoproteins released from yeast cell walls (30). In fact, addition of some mannoproteins to wine results in higher protein stability, and it has even been possible to identify specific contributions of particular mannoproteins to wine quality (7,30,37,48). Moine-Ledoux and Dubourdieu (37) identified a 32-kDa fragment of S. cerevisiae invertase capable of reducing protein haze in white wines, and similar properties were observed for the intact protein (7). Other yeast cell wall proteins have been shown to stabilize wine against p...

Oxygen Response of the Wine Yeast Saccharomyces cerevisiae EC1118 Grown under Carbon-Sufficient, Nitrogen-Limited Enological Conditions

“…Among the repressed genes, two members of the TIR genes and the HPF1 gene, all encoding cell wall mannoproteins, were found. Note that the repression of mannoproteins could have several consequences on wine quality, modulating astringency and other organoleptic properties (24). The AUS1 gene, involved in fatty acid and sterol uptake, was also repressed.…”

“…Therefore, these results indicate that it is advisable not to keep wine yeast cells at these oxygen levels for an extended period of time. Furthermore, the repression of mannoprotein genes by oxygen could also be damaging, since their presence in wine has been linked to many beneficial effects, such as increased mouthfeel, aroma retention, and astringency reduction (24). Furthermore, one of these mannoproteins (Hpf1p) is a key contributor to white wine clarification by protein haze removal (17).…”

Schizosaccharomyces japonicus: A Polysaccharide-Overproducing Yeast to Be Used in Winemaking

“…Moreover, Domizio et al [21] showed that S. japonicus releases significant amounts of polysaccharides as compared to S. pombe, thus outlining another possible utilization for these non-Saccharomyces wine yeasts in the winemaking industry. Indeed, yeast polysaccharides have many positive effects on wine quality, as they contribute to reducing protein and tartrate instability [23][24][25][26][27][28], increase the 'fullness' sensation [29], and interact with polyphenols aggregates, thus smoothing the perception of astringency [30][31][32], and retaining aromatic compounds [33,34].…”

Effect of different ageing techniques on the polysaccharide and phenolic composition and sensorial characteristics of Chardonnay white wines fermented with different selected Saccharomyces Cerevisiae yeast strains

“…They can improve the tartaric [2] and protein stability [3,4], reduce wine astringency and bitterness [5][6][7][8], enhance the mouthfeel [5,7,9] and improve the aromatic complexity and persistence [9][10][11]. In addition, they can adsorb phenolic compounds [12,13], preventing the oxidation and, therefore, the formation of browning compounds of white wines [5,14,15].…”

“…In addition, they can adsorb phenolic compounds [12,13], preventing the oxidation and, therefore, the formation of browning compounds of white wines [5,14,15]. Mannoproteins are released in the wine during alcoholic fermentation [16] and, thereafter, during yeast autolysis [3,17]. They are synthesised in the cytoplasm of yeasts, but they are not entirely used in the cell wall synthesis [18], and the excess could be released into the must during the alcoholic fermentation [19].…”