Physiological and transcriptomic analyses revealed the change of main flavor substance of Zygosaccharomyces rouxii under salt treatment

Abstract

Zygosaccharomyces rouxii was a highly salt-tolerant yeast, playing an important role in soy sauce fermentation. Previous studies reported that Z. rouxii under salt treatment produces better fermented food. However, the detailed change of main flavor substance was not clear. In this study, the physiological and transcriptomic analyses of Z. rouxii under salt treatment was investigated. The results revealed the high salt tolerance of Z. rouxii. Analysis of physiological data showed that the proportion of unsaturated fatty acids was significantly increased with the increment of salt concentrations. The analysis of organic acids showed that the content of succinic acid was significantly higher in the salt-treated Z. rouxii while oxalic acid was only identified at the 18% salt concentration-treated group. Results of volatile substances analysis showed that concentrations of 3-methyl-1-butanol and phenylethyl alcohol were significantly increased with the increment of salt concentrations. A comparison of transcriptome data showed that the genes involved in the TCA cycle and the linoleic acid synthesis process exhibited different expressions, which is consistent with the results of physiological data. This study helps to understand the change of main flavor substance of Z. rouxii under salt treatment and guide their applications in the high salt liquid state fermentation of the soy sauce.

Synergistic Fermentation with Functional Microorganisms Improves Safety and Quality of Traditional Chinese Fermented Foods

“…Yeasts may be related to synthesizing volatiles such as 2-ethylphenol and 4-ethyl-2-methoxyphenol in Pixian doubanjiang [6,34]. Z. rouxii is a functional yeast that contributes to the formation of ethanol and other volatiles such as phenylethyl alcohol, 3-methyl butanol, ethyl acetate, and phenethyl acetate in Pixian doubanjiang [35,36].…”

Identification of Volatile Markers during Early Zygosaccharomyces rouxii Contamination in Mature and Immature Jujube Honey

“…In hyperosmotic conditions, however, Z. rouxii's fatty acids were predominantly C18 and C16. There was a significant positive correlation between oleic acid (C18:1) content and osmolarity [38]. Therefore, it was hypothesized that the compound could be formed via the esterification of oleic acid derived from Z. rouxii and honey alcohol after fermentation.…”

“…2-Methyl-5-pentyl-tetrahydrofuran has a caramel flavor, and its relative concentration in the four groups increased with time after contamination. The variation may be a result of Z. rouxii's ability to degrade free amino acids via the ehrlich pathway and liberate higher alcohols and 4-hydroxyfuranones [38].…”

“…It was conceivable that these compounds derive from the TCA cycle of yeast's oxidative breakdown of carbohydrates and fatty acids in honey to the corresponding acids. In the presence of the relevant enzymes [38], it then produced by an esterification reaction with methanol that accompanied ethanol production during Z. rouxii fermentation. It is interesting to observe that yeast fermentation produced the majority of ethanol in the previous study.…”