Primary development stage, traditional fermentation industry stage, modern fermentation industry stage and biotechnology industry stage. According to information from Baidu Encyclopedia, the development of the fermentation industry can be divided into four stages, namely the original development stage, the traditional fermentation industry stage, the modern fermentation industry stage and the biotechnology industry stage. Fermentation refers to the process in which people use the life activities of microorganisms under aerobic or anaerobic conditions to prepare the microbial cells themselves, or direct metabolites or secondary metabolites.