Isolation And Identification Of Wine-Related Yeast Associated To Different Varieties

Wine fermentation is a complicated process of biotransformation, grape variety and yeast have an important connection with the quality of wine. The diversity and the composition of the yeast micropopulation contribute to the sensory characteristics of wine significantly. The diversity and identification of the wine yeast is the basic of yeast screening and strain-breeding.Since long, our country to the research of Saccharomyces cerevisiae concentrated in distilled spirit and beer mainly, the reports about wine-related yeast are less, the survey of yeast resource that play a crucial role in wine-making is being at the start stage. In this reseach, Yeasts were isolated from these sources: different grape vineyard soil, the different grape surface and the different varieties spontaneous fermentation. WL Nutrient Medium culture and physiological observation and phylogenetic analysis were performed to identify the isolates aming to reveal the diversity and the composition of the different variety related wine-yeast micropopulation isolated from Chang-li in our country.1. These yeast stains were classed by WL Nutrient Medium first. There are four types of yeast strains isolated from Cabernet Sauvignon 105 strains, the 109 yeast strains isolated from Merlot were classed into four types, and the 159 yeast strains isolated from Syrah were classed into six types. This indicated that there are some differences among the strains from the defferent varieties.2. Similarity analysis based on the RFLP of 5.8SrDNA-ITS domain,26S rRNA D1/D2 domain sequences and the sequence of 5.8S-ITS region indicated that the isolates from Cabernet Sauvignon belong to four different species: Saccharomyces cerevisiae,Hanseniaspora uvarum,Cryptococcus flavescens,Cryptococcus magnus. The isolates from Merlot belong to four different species: Saccharomyces cerevisiae,Hanseniaspora uvarum,Cryptococcus flavescens,Issatchenkia orientalis. The isolates from Syrah belong to six different species: Saccharomyces cerevisiae,Hanseniaspora uvarum,Cryptococcus flavescens,Cryptococcus aerius,Issatchenkia orientalis,Rhodosporidium toruloides. In which, Issatchenkia orientalis was detected in Merlot and Syrah, but Rhodosporidium toruloides was only found in Syrah vineyard.3. The yeast related different varieties in the process of spontaneous fermentation: The change tendency of the yeast' community about three varieties is consistent, The early stage of the alcoholic fermentation are dominated by non-Saccharomyces yeasts such as Hanseniaspora uvarum,Cryptococcus flavescens,Issatchenkia orientalis, Issatchenkia orientalis was examined in the early stage Merlot and Syrah. And Hanseniaspora uvarum is the main species which started the fermentation. Then H.uvarum bagan to decline at middle stage, S.cerevisiae increased comparing to the early stage. Later the non-Saccharomyces yeasts disappeared, and S.cerevisiae conducted the fermention to the end.4. Cryptococcus flavescens is the dominant yeast species in the three varieties grape surface, Occupies 70% above. C.magnus was examined in the surface of Cabernet Sauvignon and Issatchenkia orientalis was examined in the surface of Merlot. C. flavescens occupies 100% in the surface of Syrah. Cryptococcus flavescens is Superiority population in the soil of vineyard, few S. cerevisiae was found in Cabernet Sauvignon vineyard. R. toruloides and C. aerius were found in the soil of Syrah vineyard.