糯米发酵炸糕酵母菌的分离鉴定及优势菌株筛选

为探究天津耳朵眼炸糕工业化纯种或混种发酵中的优势酵母菌株，以耳朵眼炸糕的沥水米浆和发酵面团为原料，首先采用米浆固体培养基划线分离纯化的方法，获得6株酵母菌。其次对其进行WL培养基菌落形态观察、个体形态显微镜观察、生理生化特征测定和18S rRNA基因序列分析，发现Y2、Y3菌株为酿酒酵母（Saccharomyces cerevisiae），Y4为西文毕赤酵母（Pichia occidentalis），Y7-1、Y7-2为矮小假丝酵母（Candida humilis），Y8为溶磷白地霉（Galactomyces geotrichum）。最后测定各菌株的产气量、碳源利用率和菌体生长速度，结果显示Y2发酵产气快且产气量最大，发酵结束时发酵液中的残糖含量最低为16.33 mg，快速生长期的OD600为0.149。由此认为Y2菌株为糯米炸糕发酵生产的优势酵母菌，具有作为纯种发酵菌剂生产的潜力，为耳朵眼炸糕的品质控制和工业化生产提供了理论依据。

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

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.