Upregulation ofALD3andGPD1inSaccharomyces cerevisiaeduring Icewine fermentation

Abstract

Aims: To determine acetic acid, acetaldehyde and glycerol production by wine yeast throughout Icewine fermentation. The expression of yeast cytosolic aldehyde dehydrogenases (ALD3 and ALD6) and glycerol-3-phosphate dehydrogenase (GPD1) were followed to relate metabolites in the wines to expression patterns of these genes. Methods and Results: Icewine juice (38AE8°Brix, 401 ± 7 g l )1 sugar), diluted Icewine juice (21AE3°Brix, 211 ± 7 g l )1 sugar) and the diluted juice with sugar levels equal to the original Icewine juice (35AE6°Brix, 402 ± 6 g l )1 sugar) were fermented in triplicate using the commercial wine yeast K1-V1116. Acetic acid production increased 7AE1-fold and glycerol production increased 1AE8-fold in the Icewine fermentation over that found in the diluted juice fermentation. ALD3 showed a 6AE2-fold induction and GPD1 showed a 2AE5-fold induction during Icewine vs the diluted fermentation. ALD3 was not glucose repressed when additional sugar was added to diluted juice, but was upregulated 7AE0-fold. Conclusions:The NAD + -dependant aldehyde dehydrogenase encoded by ALD3 appears to contribute to acetic acid production during Icewine fermentation. Expression of GPD1 was upregulated in high sugar fermentations and reflects the elevated levels of glycerol. Solutes in Icewine juice in addition to sugar contribute to the yeast metabolic response. Significance and Impact of the Study: This work represents the first descriptive analysis of the fermentation of Canadian Icewine, the expression patterns of yeast genes involved in metabolite production, and their impact on Icewine quality. A role for ALD3 in acetic acid production during Icewine fermentation was found.

Cytosolic Redox Status of Wine Yeast (Saccharomyces Cerevisiae) under Hyperosmotic Stress during Icewine Fermentation

“…We have previously reported increased substrate availability for the aldehyde dehydrogenases during high sugar fermentations (acetaldehyde levels quickly rise during Icewine fermentation) [11][12][13], which was also found in this present study, along with increased expression of ALD3 encoding a cytosolic NAD + -dependent isoform over that found during dilute juice fermentation [11][12][13]. ALD3 was also the only ALD expression stimulated by acetaldehyde stress during fermentation [12].…”

“…However, under high sugar conditions of 400 g L −1 , Erasmus et al linked acetic acid generation to NADPH production via Ald6p to compensate for the downregulation of genes in the pentose phosphate pathway [15], questioning the linkage of acetic acid production under osmotic stress to glycerol formation and NADH requirements. Based on the cytosolic redox status of yeast fermenting Icewine juice at 433 g L −1 sugar, as well as our previous ALD expression analysis during Icewine fermentation [11][12][13], it appears that both Ald6p and Ald3p contribute to acetic acid during Icewine fermentation. Our data supports a linkage of acetic acid production under the high osmotic stress of Icewine fermentation to NADH requirements and glycerol production.…”

“…Past studies have linked acetic acid production during fermentation to either the NADP + cofactor system [15] or the NAD + cofactor system [11][12][13] based on ALD gene expression patterns encoding aldehyde dehydrogenases that have different cofactor requirements. We report here, for the first time, the cytosolic redox status of both cofactor systems during fermentation at two different sugar levels.…”

“…Dried wine yeast K1-V1116 was prepared using the stepwise acclimatization procedure described in Pigeau and Inglis [11]. A volume of 30 mL of the acclimatized starter culture was used to inoculate 2 L of Icewine juice (39.4 • Brix) and dilute Icewine juice (20.0 • Brix), reaching a final yeast inoculation rate of 0.5 g dry weight L −1 .…”

Sensory and chemical attributes of dessert wines made by different freezing methods of Marselan grapes

“…The intense advertence is devoted to choice of yeast strain that contributes to chemical and sensory attributes thereby question of optimal and suiTable yeast for icewine is still discussed by major of producers and researchers [7], [8], [9], [10], [11]. Before fermentation musts were clarified by Microcol bentonite alpha (Laffort CO., France) with concentration of 1g/l combined with Polylact (Laffort CO., France) for effective fining.…”