A method for microbial fermentation to produce cytosine nucleosides, characterized by comprising the following steps: Step 1: configure 200mL shake flask culture medium in a 1000mL Erlenmeyer flask, shake flask culture medium preparation method: yeast extract 5g /L, peptone 10 g/L, sodium chloride 10 g/L, sterilized in a high-pressure steam sterilizer, sterilized at 121°C, 0.1MPa for 20 minutes, cooled to room temperature and inoculated; Step 2: Configure 15L of seed tank culture medium In the 50L fermentation tank, the seed tank culture medium is: yeast extract 6g/L, peptone 12 g/L, sodium chloride 10 g/L, defoamer 0.1 g/L, high temperature steam sterilization and pressure holding 0.1MPa 、Keep the temperature at 121℃ for 15min, then cool it to 36℃. After the shake flask culture is completed, transfer the culture solution to the sterilized and cooled seed tank; Step 3: Configure 20L fermentation medium in a 50L fermentor, sterilize by high temperature and high pressure steam to maintain pressure 0.1 MPa, keep at 121°C for 15 minutes, and cool to 36°C; Step 4: After the seed tank culture is completed, transfer the seeds to the sterilized and cooled fermentor; Step 5: The stirring speed during the fermentation culture process is correlated with the DO value of the dissolved oxygen level , The correlation between the stirring speed and the DO value of the dissolved oxygen level is realized through the automatic control system of the fermentation tank.
