Species Diversity Of Wild Yeasts Collected In The East Part Of Qinghai Province Of China

In this paper, 98 natural yeast strains were isolated from the soil samples of orchard and cultivated land, collected from 10 counties (Huzhu, Minhe, Mengyuan, etc) in the east part of Qinghai Province in China. Then parts of the strains were classified according to morphologic characteristics, and were identified based on the 26S rDNA D1/D2 domain sequence analysis and physiological characterization, in order to clarify the diversity of yeast species and their distribution. Among them, 13 species belonging to 10 genera (two strains might represent two new species) were recognized. The dominant genera identified were Candida.spp, Cryptococcus.spp, Debaryomyces.spp, Hanseniaspora.spp, Geotrichum.spp, Pichia.spp, Torulaspora.spp, Issatchenkia.spp, Rhodotorula.spp and Zygowilliopsis.spp. Geotrichum candidum and Rhodotorula mucilaginosa were the most widely distributed species. The results showed that there existed abundant yeast resources and new species yeasts in the soil samples in the east part of Qinghai Province in China.98 natural yeast strains were used as the experimental samples.35 strains with high fermentation capacity and thick aroma were screened out by Durham tube method. The results of resistance evaluation and fermentation characteristics showed that 35 strains could grew in high concentration of SO2.The most strains were still normal growth and fermentation in the concentration of 600 mg/L.7 strains grew in NaCl over 120.0g/L.QXN2 strain could grow stilly normally and ferment in the concentration of 160.0g/L. Alcohol-resistance of the majority strains were low.6 strains were resist to 12%(vol) of ethanol, but did not ferment.A few yeast strains can resist high temperature, QHL4,QXS1,QJD12 strains could grow at 55℃.Their range of pH tolerance were between 2.5-12.0.Most strains could grow in 600.0g/L glucose solution and 9 of them could still ferment.9 excellent strains were screened out which fermented well and produced nice smell. The result of alcohol fermentation showed that alcoholicity of 4 yeast strains was zero, but all of them had thick aroma.4 strains alcoholicity were between 2.1-2.4%(vol),with lower residual sugar and fruit fragrant. They may be used as the ferment for the bread baking, non-alcohol beverage, waste water purification and so on.At last, the strains GS9B and GS9D were identified in detail based on morphological, physiological and biochemical characterization .There were some strains. The other characteristics of two strains were identical. Molecular taxonomic analysis based on the 26S rDNA D1/D2 domain also shows that the two strains should be defined as a new genus because they clustered in a branch alone. These new species differed from Cryptococcus spp and other genus with about 10% nucleotide divergences in the D1/D2 regions. So they were named Geotrichum brunus Xu & Liu sp. nov and Geotrichum nigrans Xu & Liu sp. nov, considering their colony morphology similar to Geotrichum spp.