Genome-wide expression analyses: Metabolic adaptation of to high sugar stress

Abstract

The transcriptional response of laboratory strains of Saccharomyces cerevisiae to salt or sorbitol stress has been well studied. These studies have yielded valuable data on how the yeast adapts to these stress conditions. However, S. cerevisiae is a saccharophilic fungus and in its natural environment this yeast encounters high concentrations of sugars. For the production of dessert wines, the sugar concentration may be as high as 50% (w/v). The metabolic pathways in S. cerevisiae under these fermentation conditions have not been studied and the transcriptional response of this yeast to sugar stress has not been investigated. High-density DNA microarrays showed that the transcription of 589 genes in an industrial strain of S. cerevisiae were affected more than two-fold in grape juice containing 40% (w/v) sugars (equimolar amounts of glucose and fructose). High sugar stress up-regulated the glycolytic and pentose phosphate pathway genes. The PDC6 gene, previously thought to encode a minor isozyme of pyruvate decarboxylase, was highly induced under these conditions. Gene expression profiles indicate that the oxidative and non-oxidative branches of the pentose phosphate pathway were up-regulated and might be used to shunt more glucose-6-phosphate and fructose-6-phosphate, respectively, from the glycolytic pathway into the pentose phosphate pathway. Structural genes involved in the formation of acetic acid from acetaldehyde, and succinic acid from glutamate, were also up-regulated. Genes involved in de novo biosynthesis of purines, pyrimidines, histidine and lysine were down-regulated by sugar stress.

Candida zemplinina Can Reduce Acetic Acid Produced by Saccharomyces cerevisiae in Sweet Wine Fermentations

“…As shown in Table 2, the EC1118 commercial strain performed worse than the two wine isolated strains, since a high level of residual sugar, associated with lower ethanol production, was detected at the end of the monitoring period. A notable production of acetic acid was concomitantly observed, most likely due to the osmotic stress provoked by the high concentration of sugars, responsible for the upregulation of the genes encoding for aldehyde dehydrogenases (12). It should be underlined that differences in the vitality counts were observed for the three S. cerevisiae strains when inoculated as pure culture in the must utilized here.…”

“…It has been shown that the response of S. cerevisiae to osmotic stress can result in increased acetic acid contents due to the upregulation of genes encoding for aldehyde dehydrogenases. In fact, yeast grown in 40% (wt/vol) sugar juice produced 1.35 g of acetic acid/liter compared to 0.3 g/liter at the lower sugar concentration (22% [wt/ vol]) (12). The acetic taste in these wines is in part masked by the high residual sugars after fermentation.…”

Carbohydrate utilization and the lager yeast transcriptome during brewery fermentation

“…Technology is now available to determine the genome-wide transcriptional response of yeast to environmental changes and has been used to elucidate the transcriptional response to a number of brewery-relevant parameters, including, for example, availability of oxygen and anaerobiosis (Aguilera et al, 2005;Lai et al, 2005), ageing (Fabrizio et al, 2005;Laun et al, 2005), dehydration and hydration (Singh et al, 2005), ethanol toxicity (Alexandre et al, 2001;Caba et al, 2005;Fujita et al, 2006;van Voorst et al, 2006), glucose repression and diauxic shift (DeRisi et al, 1997;Griffin et al, 2002), nutrient limitation (Causton et al, 2001;Gasch et al, 2000), osmotic stress (Gasch et al, 2000), oxidative stress (Causton et al, 2001;Gasch et al, 2000;Koerkamp et al, 2002), pH (Causton et al, 2001), salt stress (Caba et al, 2005), sugar stress (Ando et al, 2006;Erasmus et al, 2003) and temperature change (Causton et al, 2001;Gasch et al, 2000;Homma et al, 2003;Sahara et al, 2002). However, very few studies have utilized production strains of yeast or have involved incubation in brewery wort (Smart, 2007).…”

Wine Science in the Omics Era: The Impact of Systems Biology on the Future of Wine Research

“…Several transcriptomic studies have also been published for research conducted with wine yeast strains (Erasmus et al, 2003;Rossignol et al, 2003;Varela et al, 2005;Mendes-Ferreira et al, 2007;Marks et al, 2008;Pizarro et al, 2008;Rossouw & Bauer, 2008). These studies have illuminated the intrinsic genetic and regulatory mechanisms involved in fermentation, and have greatly increased our understanding of this important process.…”