The Study Of Breeding And Fermentation Performance Of Good Wine Yeast

Wine yeast is a single-celled microorganism that is essential to the production of wine because it converts the glucose in grape juice into ethanol and carbon dioxide.The excellent wine yeast has the characteristics of fast growth rate,strong osmotic pressure resistance,SO₂resistance,steady fermentation,high ethanol yield,and complete fermentation etc.The flavor and ethanol content of wine are also significantly influenced by fermentation performance of wine yeast.Therefore,the breeding of superior wine yeast and its fermentation performance are crucial for the wine brewing industry.Grape planting area is widespread in China,which represents diverse types and flavor characteristic wine due to different ecological conditions in various regions.However,due to the extensive application of domestic winery for foreign specific active dry yeast,the domestic wine taste convergence phenomenon was more serious.Meanwhile,foreign yeast in the process of wine production can’t completely show its excellent fermentation performance,owing to the distinction of grape varieties,cultivation conditions and brewing technology.Moreover,it can’t fully reflect the grape quality and characteristic flavor in the producing area.Therefore,it is of great significance to select good wine yeast adapted to the local climate,soil and grape varieties to make full use of microbial resources and develop high-quality characteristic wines in China.The results of the present study are obtained as follows:（1）Three strains of natural wine yeast A,B and C were obtained by extraction,separation and purification of grape orchard soil in full fruiting stage and clear tillage cultivation management stage.Three strains of yeast were analyzed and identified as yeast microorganism by preliminary identification of physiological and biochemical indexes.Then,strains A,B and C were further identified as Saccharomyces cerevisiae by 26S r DNA.（2）The fermentation performance of three natural Saccharomyces cerevisiae strains were studied with active dry yeast as the control.The results showed that the fermentation performance of three natural Saccharomyces cerevisiae strains was significantly superior than that of the control group.Three natural Saccharomyces cerevisiae strains showed high ethanol production capacity and sugar utilization,and Saccharomyces cerevisiae C produceed 7.51%alcohol and 1.5 g/L residual sugar,which is the highest among three strains.Then,three natural Saccharomyces cerevisiae strains were examined for their tolerance to ethanol,SO₂and acid,high sugar,and low temperature.Overall,it was discovered that Saccharomyces cerevisiae C demonstrated greater resilience to diverse environmental stresses.Considering its advantages in fermentation efficiency and ethanol production capability,it was determined that Saccharomyces cerevisiae C was more suitable for wine production from regional grape varieties.（3）The fermentation efficiency and ethanol production capability of Saccharomyces cerevisiae C were further enhanced by ethanol tolerance domestication and Ultraviolet（UV）and diethyl sulfate（DES）combined mutagenesis.The mutant Saccharomyces cerevisiae C-16demonstrated great genetic stability and the fermentation performance including sugar utilization and ethanol generation were significantly improved compared with the original strain.The single factor experiment was carried out by selecting five factors,the compounding ratio,fermentation temperature,inoculation quantity,SO₂,the fermentation time.Among these factors,the compounding ratio,inoculation quantity,SO₂content,and fermentation time are the major influence factors.Subsequently,the orthogonal test was carried out on the basis of the single factor experiment,which set the sensory properties and ethanol concentration of the fermented product as evaluation index.The optimum fermentation process of Saccharomyces cerevisiae C-16 for wine production was determined as follows:the compounding ratio 1:2,the inoculation amount 3%,the fermentation temperature 25℃,the fermentation time 8 days,the SO₂addition amount 150 mg/L.The fermented product has the features of amber color texture,transparent,glossy wine,elegant coordination,pure aroma,soft taste,full body and long aftertaste.