Streptococcus lactis is a kind of polypeptide substance formed by Streptococcus lactis, and its appearance appears as a light brown solid powder. It has different solubility under different pH values, and is almost insoluble in alkaline environment. Streptococcus lactis can be digested by protease in the digestive tract and converted into amino acids, and provide the body with necessary nutrients and energy sources. In addition, it has been shown that Streptococcus lactis has an inhibitory effect on most Gram-positive bacteria, bacilli and other pathogens, as well as an inhibitory effect on their reproduction and growth. Streptococcus lactis has been widely used as a natural preservative in pharmaceuticals, health food, convenience food, canned food and other medical and food preservation and storage technologies.