Isolation and Characterization of Yeast Strains from Spontaneously Fermented Tofu Whey

In traditional tofu production in Vietnam, the coagulant used is fermented tofu whey, which is the liquid separated after the coagulation of soybean proteins and is left to ferment spontaneously. There is currently limited research on the microorganisms involved in this fermentation process. This study focuses on the isolation and characterization of yeast strains from fermented tofu whey samples collected from Mơ village at different times of the year, under varying temperature and humidity conditions. Three yeast strains (Y12.1, TA18, and TA32) were selected based on preliminary sensory evaluations for further investigation. These strains were characterized to build a basic profile, including colony morphology, cell structure, and sugar utilization. Using ITS region sequencing for molecular identification, TA18, TA32 and Y12.1 were identified as Pichia kudriavzevii, Candida tropicalis and Kluyveromyces marxianus respectively. The fermentation activities of these strains in tofu whey, including pH, acidity, yeast count, and analyses of organic acids were studied. Strain TA18 demonstrated promising fermentation and sensory characteristics. The data can be used for further studies aimed at developing microbial preparations for tofu production.