Study On Identification And Tolerance Of Wine-related Yeast From Penglai And Deqin

The research on biodiversity and characteristics of wild yeast in viticulture areasand wine-producting region is a basis to the isolation of excellent yeasts, which isvaluable for the development of characteristic wine with excellent quality of China.Yeast strains are the major microorganisms during winemaking, their various speciesand population composition have a significant effect on wine sensory quality.118natural yeast strains in the paper, which were isolated from the soil collectedfrom the vineyards in Penglai of Shandong province and Deqin of Yunnan province,were classified into8types according to their cell shape, cultural characteristic andcolonial morphology on WL nutrient agar. The typical strains of8types wereidentified based on the26S rDNA D1/D2domain sequence analysis and phylogenetictree construction. The result showed that the selected yeast stains belonged to9speciesof8genera. Among them,6species of5genera were fond in Penglai region, namely,Pichia kluyveri, Hanseniaspora uvarum, Rhodotorula mucilaginosa, Candidaoleophila, Candida freyschussii, Cryptococcus laurentii;8species of8genera werefond in Deqin region, Pichia kluyveri, Hanseniaspora uvarum, Rhodotorulamucilaginosa, Candida oleophila, Metschnikowia pulcherrima, Debaryomyceshansenii, Cryptococcus laurentii, Aureobasidium pullulans, respectively.23yeast strains with high fermentation capacity were obtained from118yeaststrains by the first screening of Durham tube method, then5yeast strains with goodresistance and aroma are selected by the second screening of endurance experiments,which GenBank accession number were JQ771710, JQ771714, JQ771716, JQ771735,JQ771737, respectively. Five strains can endure12%(vol) of alcohol,600mg/L ofsulphur dioxide,600mg/L of the glucose in medium, and since they are inoculated, itwill take10dates to ferment at5℃. The alcoholicity of strain JE-22, JE-14, JE-9,YE-3, YE-4was5.4%,4.8%,4.6%,4.3%,4.0%, respectively, in the test of alcoholfermentation.Wine aroma is an important sensory index of evaluating wine quality, and thearomatic substances are also a crucial component of wine, yeast strains play asignificant role in the wine aroma. Making the best of the merits belonged tonon-Saccharomyces cerevisiae and the beneficial interactions with Saccharomycescerevisiae will effectively influence the sensory quality by mixed fermentation. Therefore, five excellent natural yeast strains (JE-22, JE-14, JE-9, YE-4, YE-3) wereinoculated in pure or mixed fermentations for dry red wine with Changli Cabernetsauvignon as raw material harvested from Hebei provence. There were14differenttreatments in all, meanwhile, the commercial yeast WH was used as a control,spontaneous fermentation as a blank experiment. As a result, the physiochemicalindexes of14wine samples made by single strain fermentation or by combined strainsfermentation were in accord with international standards of wine. GC/MS analysis ofaromatic compounds showed that YE-3+YE-4was an ideal combination, and the wine(13#) had soft taste as well as mellow aroma. The remarkable differences between thetype and the content of aroma components in all samples indicated that different yeaststrains had a great influence on the style of characteristics wine.