Distribution and function of dominant yeast species in the fermentation of strong-flavor baijiu.

The role of the yeast community in Chinese strong-flavor baijiu fermentation was investigated by culture-independent and culture-dependent methods based on 26S rDNA sequence analysis. 92 yeast species belonging to 54 genera were found by Illumina sequencing during the fermentation of strong-flavor baijiu "Wuliangye" and 306 strains belonging to 28 species, which covered all species with more than 1% of relative abundance, were isolated and identified. Kazachstania exigua, Geotrichum silvicola, Pichia kudriavzevii, Saccharomyces cerevisiae, Zyosaccharomyces bailii, and K. humilis were found to be the first six dominant species, and their proportion varied with different fermentation stages. K. exigua was the most important yeast species responsible for the production of ethanol with the assistance of P. kudriavzevii and Z. bailii in the vigorous stage and P. kudriavzevii and G. silvicola in the continuous fermentation stage. Higher alcohols were mainly produced by K. exigua, P. kudriavzevii, S. cerevisiae, and Z. bailii in the vigorous fermentation stage, which was stimulated by more oxygen in the grains of the upper strata. K. exigua, P. kudrizevii, S. cerevisiae, Z. bailii, G. silvicola, and Trichosporon ovoides promoted the formation of ethyl alcohol. The results revealed the key roles of K. exigua, G. silvicola, and P. kudriavzevii in the fermentation of strong-flavor baijiu. The functions of these species should be confirmed by a further study based on the fermentation characteristics of isolated yeast strains gathered in this study. Distribution and function of dominant yeast species in the fermentation of strong flavor baijiu.