Different Gene Expression Patterns of Hexose Transporter Genes Modulate Fermentation Performance of Four Saccharomyces cerevisiae Strains

Chiara Nadai,Alessio Giacomini,Giulia Crosato,Viviana Corich

doi:10.3390/fermentation7030164

Chiara Nadai, Alessio Giacomini + Show 2 more

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https://doi.org/10.3390/fermentation7030164

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Journal: Fermentation	Publication Date: Aug 23, 2021
Citations: 6	License type: CC BY 4.0

Affiliation: University of Padua

Abstract

In Saccharomyces cerevisiae, the fermentation rate and the ability to complete the sugar transformation process depend on the glucose and fructose transporter set-up. Hexose transport mainly occurs via facilitated diffusion carriers and these are encoded by the HXT gene family and GAL2. In addition, FSY1, coding a fructose/H+ symporter, was identified in some wine strains. This little-known transporter could be relevant in the last part of the fermentation process when fructose is the most abundant sugar. In this work, we investigated the gene expression of the hexose transporters during late fermentation phase, by means of qPCR. Four S. cerevisiae strains (P301.9, R31.3, R008, isolated from vineyard, and the commercial EC1118) were considered and the transporter gene expression levels were determined to evaluate how the strain gene expression pattern modulated the late fermentation process. The very low global gene expression and the poor fermentation performance of R008 suggested that the overall expression level is a determinant to obtain the total sugar consumption. Each strain showed a specific gene expression profile that was strongly variable. This led to rethinking the importance of the HXT3 gene that was previously considered to play a major role in sugar transport. In vineyard strains, other transporter genes, such as HXT6/7, HXT8, and FSY1, showed higher expression levels, and the resulting gene expression patterns properly supported the late fermentation process.

Highlights

In wine alcoholic fermentation, glucose and fructose present in grape must are cofermented by yeasts to ethanol and carbon dioxide
The aim was to check strain behavior during the alcoholic fermentation focusing on the last part of the considered statistically significant for p-value lower than 0.05
The aim was to check strain behavior during the alcoholic fermentation focusing on the last part of the fermentation, starting half the expected total expected

Summary

Introduction

Glucose and fructose present in grape must are cofermented by yeasts to ethanol and carbon dioxide. Fructose is used concomitantly with glucose, the latter is the first sugar to be depleted from the medium during fermentation [2,3]. Fructose becomes the main sugar present during the late stages of alcoholic fermentation, and wine yeasts have to ferment this non-preferred sugar in the presence of large amounts of ethanol. It has been reported that stuck fermentations are frequently characterized by an unusually high fructose-to-glucose ratio [2]. The ability of wine yeasts to ferment fructose is critically important for the maintenance of a high rate of fermentation at the end of the process and for fermentation of the must to dryness. The reasons for the difference between the glucose fermentation rate and the fructose fermentation rate are unclear, but one of the first steps in hexose metabolism is generally thought to be involved [1]

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