Bacterial fermentation is a biological process that uses the special metabolic pathway of bacteria to transform raw materials into target products. There is no difference between bacterial fermentation and yeast fermentation in essence, but they use different strains, one is yeast and the other is bacteria. Bacterial fermentation can be divided into anaerobic and aerobic, and there are many fermentation methods. The products are rich and varied, and they are used up. Fermentation bacteria have simple structure and many special metabolic pathways, which make its formula rough, raw materials cheaper, sensitive to the environment and easy to improve. At present, they are the most widely used.