Correlation between acetaldehyde and ethanol resistance and expression of HSP genes in yeast strains isolated during the biological aging of sherry wines

Abstract

In the production of sherry wines, the process of biological aging is essential for the development of their organoleptic properties. This process involves velum formation by "flor" yeasts. Several of these yeast strains have been isolated and characterized with regard to their genetic, physiological and metabolic properties. In this work, we studied their resistance to cold-, osmotic-, oxidative-, ethanol- and acetaldehyde-stress, and found, in most cases, a correlation between resistance to acetaldehyde stress and ethanol stress and isolation from "soleras." Moreover, gene expression analysis revealed induction of the heat shock protein (HSP) genes HSP12, HSP82, and especially HSP26 and HSP104, under acetaldehyde stress in most of the strains. In strain C, there was a clear correlation between resistance to ethanol and acetaldehyde, the high induction of HSP genes by these compounds and its presence as the predominant strain in most levels of several soleras.

Response to acetaldehyde stress in the yeast Saccharomyces cerevisiae involves a strain‐dependent regulation of several ALD genes and is mediatedby the general stress response pathway

“…The conditions described by Aranda et al (2002) were applied for the systematic analysis of ethanol and acetaldehyde stresses. Yeast cells were grown with vigorous orbital agitation at 30 • C in YPD (1% w/v yeast extract, 2% bactopeptone and 2% glucose), YPE (the same medium but containing 2% ethanol v/v instead of glucose) or, in the case of laboratory strains, synthetic growth medium (SD: 2% glucose, 0.67% w/v yeast nitrogen base without amino acids) containing the appropriate amounts of nucleotides and amino acids (Aranda et al, 2002).…”

“…Yeast cells were grown with vigorous orbital agitation at 30 • C in YPD (1% w/v yeast extract, 2% bactopeptone and 2% glucose), YPE (the same medium but containing 2% ethanol v/v instead of glucose) or, in the case of laboratory strains, synthetic growth medium (SD: 2% glucose, 0.67% w/v yeast nitrogen base without amino acids) containing the appropriate amounts of nucleotides and amino acids (Aranda et al, 2002). Yeast cells from overnight cultures were maintained in exponential growth for 2 days prior to stress treatment.…”

“…Acetaldehyde concentrations of 300-400 mg/l are commonly reached, but in some cases values of up to 1000 mg/l can be found (Martínez et al, 1997a(Martínez et al, , 1998. Wine yeasts population dynamics between alcoholic fermentation and biological ageing are influenced by their ability to produce acetaldehyde, the rate of film formation (Ibeas et al, 1997;Martínez et al, 1997a), and a higher resistance to the stress conditions taking place during biological ageing of sherry wines (Aranda et al, 2002).…”

“…Less is known about the molecular responses to acetaldehyde stress. Significant induction of HSP genes occurs in both industrial and laboratory strains and the highest levels were found in the most ethanol-and acetaldehyde-resistant strains (Aranda et al, 2002).…”

“…By comparing these strains we can also gain a better understanding of the advantages of flor yeasts to conduct biological ageing of sherry wines. For flor yeasts a correlation exists between resistance to ethanol and acetaldehyde and involvement in biological ageing (Aranda et al, 2002). Consequently, it would be interesting to know whether or not acetaldehyde dehydrogenases could play a role in this natural process of strain ALD gene expression under ethanol and acetaldehyde stress 749 selection.…”