Isolation, Identification, and Screening of Dominant Yeast Strains in Fried Cake Made from Natural Fermented Glutinous Rice

Abstract:

To explore the dominant yeast strain in industrial pure or mixed fermentation during the preparation of Tianjin erduoyan fried cake, the rice slurry and fermented dough were used as experiment material, and six yeast strains were separated and purified by the streak plate method using slurry solid culture medium.Based on observations of colony morphology in Wallerstein Laboratory (WL) medium and individual cell morphology, determination of physiological and biochemical characteristics, and 18S rRNA gene sequence analysis, strains Y2 and Y3 were identified as Saccharomyces cerevisiae and strain Y4 was identified as Pichia occidentalis. Besides, Y7-1 and Y7-2 were identified as Candida humilis, and Y8 was identified as Galactomyces geotrichum. Gas production, carbon source utilization rate, and cell growth rate of each strain were determined. Results showed that Y2 had a fast gas production rate and the highest gas production. At the end of fermentation, the content of residual sugar in the fermentation broth was the lowest (16.33 mg), and the optical density at 600 nm (OD600) during exponential growth phase was 0.149. Thus, strain Y2 is the dominant yeast in the production of fried fermented glutinous rice cake, and has the potential to be a pure fermentation agent. This study provides a theoretical basis for the quality control and industrial production of erduoyan fried cake.