Metabolite Profiling during Fermentation of Makgeolli by the Wild Yeast Strain Saccharomyces cerevisiae Y98-5

Abstract

Makgeolli is a traditional Korean alcoholic beverage. The flavor of makgeolli is primarily determined by metabolic products such as free sugars, amino acids, organic acids, and aromatic compounds, which are produced during the fermentation of raw materials by molds and yeasts present in nuruk, a Korean fermentation starter. In this study, makgeolli was brewed using the wild yeast strain Saccharomyces cerevisiae Y98-5, and temporal changes in the metabolites during fermentation were analyzed by ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. The resultant data were analyzed by partial least squares-discriminant analysis (PLS-DA). Various metabolites, including amino acids, organic acids, sugar alcohols, small peptides, and nucleosides, were obviously altered by increasing the fermentation period. Changes in these metabolites allowed us to distinguish among makgeolli samples with different fermentation periods (1, 2, 3, 6, 7, and 8 days) on a PLS-DA score plot. In the makgeolli brewed in this study, the amounts of tyrosine (463.13 µg/mL) and leucine (362.77 µg/mL) were high. Therefore, our results indicate that monitoring the changes in metabolites during makgeolli fermentation might be important for brewing makgeolli with good nutritional quality.

Effects of Schiff Base Formation and Aldol Condensation on the Determination of Aldehydes in Rice Wine Using GC-MS

“…Hydroxyl carbonyl compounds are intermediates of aldol condensation and are more readily produced in basic states. Hydroxyl carbonyl compounds can be converted to unsaturated carbonyl enones, which are stable and irreversible [ 15 ]. Most hydroxyl carbonyl compounds are increased at basic pH, whereas hydroxyl acetaldehydes are increased by the neutral state and are decreased under basic conditions.…”

“…Most hydroxyl carbonyl compounds are increased at basic pH, whereas hydroxyl acetaldehydes are increased by the neutral state and are decreased under basic conditions. This phenomenon can occur due to the conversion of a hydroxyl acetaldehyde to an unsaturated carbonyl enone, which is relatively stable [ 15 ]. However, the reduction of aldehydes also could be explained by Schiff base formation, because it is accelerated by base catalysis.…”

“…The contents of organic acids generally increased during the fermentation period [ 15 ]. On the other hand, the maximum content of citric acid, which represents the largest amount of carboxylic acid in makgeolli , was obtained at the seventh day of fermentation, after which its levels decreased [ 15 ].…”

Comparative analysis of nonvolatile and volatile metabolites in Lichtheimia ramosa cultivated in different growth media

“…The metabolites in fermented foods such as soy sauce, makgeolli, doenjang, and cheonggukjang, Korean traditional fermented soybean pastes, and related starter cultures including koji and nuruk have been investigated previously. 8,[23][24][25][26][27][28][29] Microbial metabolites have also been analyzed for studying the unique chemical fingerprints of metabolite profiles, with characterization of the micro-organisms. 30,31) In particular, the characteristics of metabolites of yeasts such as Saccharomyces cerevisiae and fungi such as Aspergillus, Penicillium, and Rhizopus species have been compared.…”

“…28,30,42) The diverse metabolites related to unique aromas, flavors, and textures are produced and influenced by the associated microbiological processes. 43) The metabolites in nuruk fermented with specific microorganisms such as A. oryzae have been profiled previously, 25,26,44) but no previous study has analyzed the nonvolatile and volatile metabolites of L. ramosa isolated from nuruk. The objective of the current study was to investigate the nonvolatile and volatile metabolites of L. ramosa cultivated in different media using GC-TOF-MS and GC-MS, respectively.…”