Abstract
The most important dogma in white-wine production is the preservation of the wine aroma and the limitation of the oxidative action of oxygen. In contrast, the aging of Sherry and Sherry-like wines is an aerobic process that depends on the oxidative activity of flor strains of Saccharomyces cerevisiae. Under depletion of nitrogen and fermentable carbon sources, these yeast produce aggregates of floating cells and form an air–liquid biofilm on the wine surface, which is also known as velum or flor. This behavior is due to genetic and metabolic peculiarities that differentiate flor yeast from other wine yeast. This review will focus first on the most updated data obtained through the analysis of flor yeast with -omic tools. Comparative genomics, proteomics, and metabolomics of flor and wine yeast strains are shedding new light on several features of these special yeast, and in particular, they have revealed the extent of proteome remodeling imposed by the biofilm life-style. Finally, new insights in terms of promotion and inhibition of biofilm formation through small molecules, amino acids, and di/tri-peptides, and novel possibilities for the exploitation of biofilm immobilization within a fungal hyphae framework, will be discussed.
Highlights
Saccharomyces cerevisiae flor yeast are responsible for the biological aging of Sherry and Sherrylike wines
The use of microsatellite genotyping has revealed that flor yeast are a group of S. cerevisiae strains close to wine strains, and given the contrasting life-styles of these two groups, this makes for an interesting model for the study of yeast adaptation to anthropic niches
The exploitation of other comparative -omic tools has provided novel knowledge on several features of flor yeast, and has revealed that proteome remodeling under biofilmforming conditions might be related to the production of aroma-properties-related metabolites
Summary
Saccharomyces cerevisiae flor yeast are responsible for the biological aging of Sherry and Sherrylike wines. As well as the role of FLO11 in the rising of cells and in their hydrophobicity, biofilm formation appears to be dependent on increased cell buoyancy This is influenced by their lipid content and composition, as flor strains have greater chain lengths and unsaturation levels of their fatty-acid residues than those shown by non-biofilm-forming strains of S. cerevisiae (Farris et al, 1993; Zara et al, 2009). Inositol availability affects biofilm formation, possibly due to its key role in the assembly of the glycosylphosphatidylinositol anchor of Flo11p, and in the regulation of lipid biosynthetic genes, such as ACC1 (Zara et al, 2012) Due to their metabolic and genetic peculiarities, flor strains can overcome stress caused by high ethanol and acetaldehyde contents in Sherry and Sherry-like wines (Budroni et al, 2005). We will report on new insights in terms of promotion and inhibition of biofilm formation through small molecules, amino acids and di/tripeptides, and on novel possibilities for the exploitation of yeast immobilization within a fungal hyphae framework
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