The dissolved oxygen concentration is insufficient, and there is no stirring and ventilation above 35℃. It is necessary to control the oxygen concentration in different stages of fermentation, stir and ventilate, and control the temperature below 35℃ to prevent lysine fermentation from turning sour. Lysine is one of the essential amino acids in human body, which can promote human development, enhance immune function and improve the function of central nervous system. Lysine is an essential amino acid. Because the content of lysine in cereal food is very low, and it is easy to be destroyed and lacked during processing, it is called the first restrictive amino acid.