Explain why sterile air is introduced after the fermentor is emptied to keep the pressure of the fermentor at 0.05mpa.

After elimination, avoid material backflow and pollution, adjust gas exchange rate and maintain appropriate gas partial pressure to prevent the invasion of external air or microorganisms.

1. Avoid backflow and pollution of sterilized materials: after sterilization, the internal pressure of the fermentor is low, and no sterile air is introduced to maintain a certain tank pressure, which will cause external air or pollutants to flow back into the tank and pollute the air pipeline and filter media.

2. Adjust the gas exchange rate and keep proper gas partial pressure: By controlling the pressure in the tank, the gas exchange rate in the fermentation process can be adjusted. Proper gas exchange is very important for maintaining the partial pressure of gas and balancing the accumulation of fermentation products during fermentation.

3. Prevent the invasion of outside air or microorganisms: Introducing sterile air into the tank can effectively prevent the invasion of outside air or microorganisms. In the fermentation process, the invasion of external air or microorganisms will interfere or pollute the fermentation process, affecting the quality and stability of fermentation.