The Isolation And Identification Of Yeast Strains From Xifeng-Flavor Daqu

To investigate the diversity of yeast from Xifeng-Daqu,177 yeast strains were isolated by the traditional culture-based techniques,and their characteristics were determined by 5.8S rDNA-ITS PCR-RFLP,while utilization of sole source carbon and nitrogen were tested.On the base of sequences analyses of 5.8S rRNA-ITS and 18S rRNA genes,the phylogentic relationship was revealed.The microbial communities and the composition of yeast in the Daqu during the culture periods were studied and will provide us their potential function in production of liquor.The results were showed as follows:During the fermentation of Daqu,the number of yeast increased at first,then decreased and trended to stable at last.During the first ten days,the yeast displayed an rapid growth to the highest peak,which might be resulted from the temperature of Daqu itself.Based on the combined result of the PCR-RFLP and phologenetic analysis of 5.8S rRNA-ITS and 18S rRNA genes,177 yeast strains were classified into nine species of seven genus,including Cryptococcus albidus,Clavispora lusitaniae,Pichia anomala,Pichia kudriavzevi,Pichia fermentans,Saccharomycopsis fibuligera,Saccharomyces cerevisia,Torulaspora delbrueckii and Trichosporon brassicae.Among them,Saccharomycopsis fibuligera and Pichia anomala were predominant groups.The strains of Saccharomycopsis fibuligera and Pichia anomala made up 48%and 31.6%in number,respectively.All of the 10 representative yeast strains showed the assimilation capacity to glucose,D-ribose,D-galactose,D-mannose,D-trehalose,sucrose,maltose,ethanol,ammonium sulfate,alanine as the sole carbon source or nitrogen source.And they were unable to make use of isoamyl alcohol and benzyl alcohol as the sole carbon source.As the predominant yeast species,Saccharomycopsis fibuligera cannot use L-rhamnose,lactose,starch,citric acid,glycerin,DL-lactic acid,mannitol,inositol,methanol,isopropyl alcohol,isoamyl alcohol,benzyl alcohol,sodium nitrite as the sole carbon source or nitrogen source,and can use glucose,fructose,D-ribose,D-galactose,arabinose,D-xylose,D-mannose,sucrose,maltose,raffinose,D-fucose,ethanol,sodium nitrate,ammonium sulfate,alanine as sole carbon source or nitrogen source;Pichia anomala can use all carbon source and nitrogen source as the sole carbon source or nitrogen source,except isoamyl alcohol and benzyl alcohol.