The Isolation And Identification Of Wine-related Yeast From Viticultutal District Of Gansu Province

Alcoholic fermentation is one of the main phases in wine production. Yeasts play a central role in the fermentation process during winemaking. 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.No reports were found about the wine yeast diversity of our country, and the wine yeast resource has not discovered by far. The Wu-wei and Gao-tai grape ditrict are belong to cool-temperate arid region, which is abundant yeast resources and becoming to the most competitive of quality wine.Yeasts were isolated from these source: winery equipment surfaces, the grape surface and the spontaneous fermentation must of the Qi-lian and the Mo-gao wineries. WL Nutrient Medium culture and physiological observation and phylogenetic analysis were performed to identifify the isolates aming to reveal the diversity and the composition of the yeast micropopulation.1. These yeast stains were classed by WL Nutrient Medium first. There are 10 types of yeast strains isolated from MoGao winery, and the yeast strains isolated from QiLian winey were classed into 7 types. This indicated that there is big differences between the strains from the two defferent wineries.2. Similarity analysis based on 26S rRNA D1/D2 domain sequences and the sequence of 5.8S-ITS region indicated that the isolates from MoGao winery belong to 10 different species: Metschnikowia pulcherrima,Hanseniaspora uvarum,Issatchenkia orientalis,Pichia fermentans,Pichia kluyveri,Saccharomyces cerevisiae,Cryptococcus magnus,Cryptococcus uzbekistanensis,Rhodosporidium kratochvilovae,Rhodotorula mucilaginosa. and the isolates from QiLian winery belong to 7 different species: Saccharomyces cerevisiae,Issatchenkia orientalis,Pichia anomala,Rhodotorula mucilaginosa,Cryptococcus magnus,Cryptococcus flavescens,Hanseniaspora uvarum.3. C.magnus and R. mucilaginosa is the dominant yeast species in the soil of Mo-Gao vineyard, and the surface of equipment is predominanced by Hanseniaspora uvarum. And the surface of grape is predominanced by H. uvarum and I. orientalis in Qi-lian winery. 4. They are four spontaneous fermentation must were studied, and the changes of the wine-related yeast micropopulation is below:The early stage of the alcoholic fermentation are dominated by non-Saccharomyces yeasts such as M.pulcherrima,H.uvarum,Pichia kluyveri var. kluyveri,I. orientalis, and H.uvarum is the main species which started the fermentation. Then H.uvarum bagan to decline at middle stage, and M.pulcherrima together with S.cerevisiae increased comparing to the early stage. Later the non-Saccharomyces yeasts disappeared, and S.cerevisiae conducted the fermention to the end.5. 26S rDNA D1/D2 domain sequences analysis of strain C248-K reveals that it inhabits 98.8% identities with Pichia fermentans, while the strain C84 inhabits 98.9% identities with Metschnikowia pulcherrima. The identification of these two strains need further investigation.