Study On Yeast Diversity And Fermentation Characteristics Of Luzhou-flavor Liquor Fermented Grains

Taking fermented grains at different fermentation stages and at different levels in a multigrain luzhou-flavor distillery in yibin city,sichuan province as the research object,the method of combining no-culture and pure culture was adopted to reveal the diversity and spatial and temporal distribution characteristics of the dominant yeast community in luzhou-flavor liquor fermented grains on the whole.The relationship between the key yeasts and the main volatile substances in fermented grains was analyzed by means of in situ fermentation,and the physical and chemical indexes and volatile substances in fermented grains were dynamically detected by conventional methods and headspace-solid-phase microextraction and gas chromatographymass spectrometry(HS-SPME GC-MS).Finally,pure yeast solid fermentation was carried out on the key yeast obtained from pure culture,and the fermentation characteristics of the key yeast in luzhou-flavor liquor fermentation were further analyzed by combining the in-situ fermentation characteristics of each dominant yeast species and genera.It was found that:(1)fifty-four genera and 92 species of yeast were detected in fermented grains by highthroughput sequencing.Among them,the dominant species were yeast Kazachstania exigua,Geotrichum silvicola,Pichia kudriavzevii,Saccharomyces cerevisiae,Zygosaccharomyces bailii,Kazachstania humilis,which showed different spatial and temporal distribution characteristics in the whole fermentation process of upper and lower fermented grains.The 306 yeast strains isolated and identified by the culture omics method based on the results of highthroughput sequencing analysis were divided into 28 species,covering all the yeast species with abundance greater than 1% in the culture-free analysis.(2)discovered 40 d before fermentation Zygosaccharomyces bailii,Geotrichum silvicola,Kazachstania exigua,Pichia kudriavzevii,Saccharomyces cerevisiae and Kazachstania humilis in distilled grains in the production of ethanol,at 0 d-12 d Kazachstania sp.,Geortrichum silvicola,Saccharomyces cerevisiae and Zygosaccharomyces bailii may be involved in the production of yan-phenyl ethanol,3-furfuryl alcohol and iso-amyl alcohol in grains.In the continuous fermentation stage,Kazachstania sp.,Pichia kudriavzevii and Geortrichum silvicola could produce a small amount of yan-phenyl ethanol,3-furfuryl alcohol and iso-amyl alcohol.The rapid increase in contents of ethyl acetate,ethyl caproate and ethyl butyrate in fermented grains at 4 d-12 d was due to the participation of Kazachstania sp.,Geortrichum silvicola,Saccharomyces cerevisiae and Zygosaccharomyces bailii,and the increase in the sustained fermentation stage might be related to the participation of Geortrichum silvicola and Pichia kudriavzevii.(3)bacteria by pure solid fermentation,found Geortrichum silvicola this 2 strains of yeast is the main volatile substances,isoamyl acetate,ethyl acetate and beta benzyl ethanol,Kazachstania genera and Pichia kudriavzevii main volatile products for: phenylethyl alcohol and carbon 14 or more senior fatty acid ethyl ester,but with distilled grains fermentation have certain differences in situ,later will use mixed bacteria fermentation properties of solid state fermentation further resolve the yeast.