Effects Of Glutathione On Growth Characteristics Of Non-Saccharomyces Cerevisiae And Metabolites Of Fermentation Broth

Non-Saccharomyces cerevisiae have positive effects on the sensory characteristics of wine,but they cannot be used independently in alcoholic fermentation because of low ethanol transformation.And there are also problems such as browning oxidation,flavor loss and high organic acid content of fermentation broth.Glutathione(GSH)has unique redox and nucleophilic properties,and makes a contribution to flavor and quality improvement of wine.However,the regulation role of GSH in yeast growth and metabolism remains unclear.In order to develop redox regulation strategies to enhance the growth and fermentation capacity of non-Saccharomyces and improve the quality characteristics of fermentation broth,different concentrations of GSH(0-100 mg/L)were added prior yeast culture,alcoholic fermentation and aging storage to investigate the effects of GSH on the growth,stress and fermentation characteristics of non-Saccharomyces cerevisiae and discuss the influence of volatile and non-volatile metabolites and metabolic changes in fermentation broth.The main results are as follows:(1)Exogenous GSH can promote intracellular accumulation of GSH in non-Saccharomyces cerevisiae and improve its viability and biological performance under ethanol and acid stress of non-Saccharomyces.The contents of extracellular GSH,oxidized glutathione(GSSG)and glutathione peroxidase(GPX)activity were significantly increased during fermentation,and population of yeasts in 0-3 days,ethanol production,reducing sugars and organic acids consumption were increased in 10mg/L GSH-added wines.(2)GSH-added fig wines had higher contents of amino acids,and intracellular β-glucosidase and pectinase activities were enhanced.10mg/L GSH addition had a significant protective effect on the oxidation of phenols,flavonoids and terpenoids,and significantly increased the contents of chlorogenic acid and epicatechin in fermentation broth.Under the condition of long-term storage,GSH effectively improved the softness index of fig wine and reduced malic acids content.GSH also alleviated chemical oxidation and raised the red tone during storage.(3)Gas chromatography mass spectrometry and liquid chromatography tandem mass spectrometry were performed to determine53 main volatile metabolites,184 and 153 non-volatile metabolites in positive/negative mode.GSH-added fig wines had higher contents of volatile alcohols and acetate ester compared with traditional fig wines,and the loss of terpene aroma was effectively inhibited.20 non-volatile metabolites were defined as potential biomakers of which oxidized glutathione,L-cystathionine,α-ketoisovalerate,L-2-aminoadipate and4-aminobutanoate were up-regulated.Metabolic enrichment analysis showed that amino acids biosynthesis and degradation,purine metabolism and TCA cycle were important metabolic activities related to the fermentation process of exogenous GSH culture.