Exploration of Genomic Features and Volatile Flavor Production of Yeasts Isolated from Commercial Korean Rice Wine Makgeolli

초록

In this study, we identified and characterized yeast strains isolated from commercially available Korean rice wine, Kooksoondang Yetnal (KY), Haechang (HC), Yangchon Ureongii (YU), and Cheongju Sinseonju (CS) makgeolli products. ITS sequence analysis identified all the yeast isolates as Saccharomyces cerevisiae. Most makgeolli isolates exhibited better growth at 15°C than the reference strain S. cerevisiae S288C. Ploidy and whole-genome sequencing analyses of six representative strains revealed that all strains possessed diploid genomes. Phylogenetic analysis based on genome sequences indicated that all makgeolli strains clustered with the Asian-origin sake/ragi lineage. HC-CAU28, KY-CAU1, KY-CAU18, and YU-CAU13 were closely related to the Japanese sake strain K7, whereas CS-CAU12 and CS-CAU26 shared a common ancestor with the Chinese industrial bioethanol strain YJSH1 and Indonesian ragi strain Y9. Compared to S288C, the makgeolli isolates displayed similar volatile flavor profiles but produced higher levels of several flavor compounds, including acetoin, diacetyl, and benzaldehyde, consistent with higher expression of the corresponding biosynthetic genes. Notably, HC-CAU28, KY-CAU1, KY-CAU18, and YU-CAU13 did not produce a clove-like flavor 4-vinylguaiacol (4-VG), reflecting the presence of a nonsense mutation in their FDC1 genes encoding ferulic acid decarboxylase involved in conversion of ferulic acid to 4-VG. The 4-VG production activity of the fdc1 mutant strains was recovered by introducing FDC1 overexpression vectors except YU-CAU13. These findings on flavor production capacity of commercial makgeolli yeast strains, based on genomic information and validated with genetic manipulation, would provide a foundation for developing yeast starters tailored for rice wine with optimized sensory and functional properties.

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