Optimization of Medium Composition and Culture Conditions for Cell Multiplication of a High Quality Milk Beer Fermentation Yeast (Kluyveromyces marxianus)

Milk beer is a distinctive alcoholic milk drink created in China, and increasingly popular with consumers. Yeast is key factor to its fermentation production, and determines the flavor and quality. In this investigation, a high-quality yeast Kluyveromyces marxianus MJ1 suitable for milk beer fermentation was utilized in an optimization study of proliferation culture. Results showed that using the optimal medium composition: wort-based medium supplemented with molasses 2.94%, wheat bran 1.56%, CaCO3 0.21%; and applying the optimal culture conditions: 28 °C, rotation speed 220 rpm, inoculation concentration 1.5×106 CFU·mL−1, the viable count of MJ1 reached a maximum of 7.8×108 CFU·mL−1. Compared to YPD broth, the viable count of MJ1 increased to 4.11 times, while the raw material cost decreased to about 1/6 of the cost of YPD broth. The study achieved high-density proliferation culture of MJ1 through usage of low cost crop by-products; and laid the foundation for preparation of active freeze-dried powder for applications in the milk beer industry.