Modern fermentation processes include a variety of fermentation methods, such as fed batch fermentation and continuous fermentation. This paper will focus on the principles and case studies of these two methods. Fed batch fermentation originates from fractionation fermentation with closed culture and adjustment of the pH value of the carbon source, to which the process of feeding the carbon source to the cell culture in a controlled manner has been added. This type of fermentation is more commonly used compared to the other. Continuous fermentation is also a closed fermentation system, which can operate without restrictions by continuous or intermittent addition of fresh nutrient media to the fermenter; however, it is susceptible to contamination by stray bacteria and metabolic inconvenience.