Screening, identification and properties of osmophilic yeast from raspberry Jiaosu during natural fermentation process

In order to get excellent osmophilic yeast strains for the production of microbial fermentation of plant products, three strains from raspberry Jiaosu were isolated and screened.And the morphological, physio-biochemical characteristics as well as26 S r DNA gene sequence analysis were used to identify the strains.The results showed that the morphological features of Y1, Y2 and Y3 were similar to each other, and they could grow at very high sugar concentrations. The sequences of three isolated osmophilic strains showed a high degree ( > 99%) of homology to those reported in Genbank and they were finally indentificated as Zygosaccharomyces rouxii ( Z.rouxii) . In the study, Z. rouxii could grow at the initial glucose concentration of 300, 450, 600 and 750 g/L and the lag phase were 12, 12, 36 and 60 h, respectively. The strain growed extremely slowly at initial glucose concentration of 900 g/L.When intial p H values were 2.5, 3.0 and 3.5, the adapted strain responded with a lag phase of 96, 48 and 48 h, respectively, and no growth was abserved at intial p H1.5 and 2.0. Z. rouxiiwas the dominant yeasts in raspberry Jiaosu, and it was a sugar-tolerant and low p H tolerated yeast.