Abstract
Grape-derived proanthocyanidins could act as a protector against various environmental stresses for Saccharomyces cerevisiae during wine fermentation, resulting in the increased physiological activity, fermentation efficiency and improved wine quality. In order to explore the possible protection mechanism of proanthocyanidins globally, RNA-seq analysis for wine yeast AWRI R2 cultivated with 0 g/L (group A), 0.1 g/L (group B), 1.0 g/L (group C) proanthocyanidins were applied in this study. Differentially expressed genes were enriched into six metabolic pathways including vitamin B6, thiamine, amino acids, aminoacyl-tRNA, carbohydrate and steroid based on KEGG enrichment analysis. Four key genes (SNZ2, THI6, THI21 and THI80), participated in the biosynthesis of vitamin B6 and thiamine, were up-regulated significantly in proanthocyanidins treated yeast cells and the gene expression levels were verified by RT-qPCR. Yeast cells supplemented with proanthocyanidins performed increased intracellular levels of vitamin B6 and thiamine and higher cell viability compared to the control group. In addition, the composition of intracellular fatty acids showed an obvious alternation in proanthocyanidins-treated yeast cells, in which the UFAs content increased whereas the SFA content decreased. In general, we provided an indirect protection effect of proanthocyanidins on the yeast cells to alleviate environmental stresses during wine fermentation.
Highlights
The widely distributed phenolic substances in wine refer to a large group of chemical compounds that impact the sensory quality of red wine, such as color, flavor and astringency[1]
To testify whether the PAs show the similar effects on alternation of lipid metabolism and yeast tolerance for environmental stresses, we studied the changes in fatty acid profile in the yeast cells with or without the treatment of PAs
RNA-seq analysis was employed in our study to systematically explore the protection mechanism of PAs on the yeast cells during wine fermentation
Summary
The widely distributed phenolic substances in wine refer to a large group of chemical compounds that impact the sensory quality of red wine, such as color, flavor and astringency[1]. A large number of studies have shown that these phenolic substances have biological activities of interest to the consumers, such as antioxidant properties, vascular protection and immune-modulatory effects[2,3,4,5] These phenolic compounds are mainly extracted from grape skin, seed, and stem during the maceration and fermentation process[6]. In order to carry out wine fermentation properly, yeast cells should possess the capacity of rapid stress perceptions and responses to those stress conditions without substantial viability loss[14] To solve these problems, a number of previous studies have been performed in the aspects of robust strain isolation, genetic modification and fermentation process control[18,19,20,21]. In this study, we employed RNA-seq as the method to find the differentially expressed key genes and performed comprehensive and comparative bioinformatics analysis to globally explore the possible protective effects of PAs on the yeast cells during wine fermentation
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