ε-Polylysine is a light yellow powder with strong hygroscopicity and slightly bitter taste. It is a linear polymer of lysine. It is produced by streptomyces fermentation and has a broad-spectrum antibacterial effect. ε-polylysine is polymerized by 25-30 lysine groups, which is relatively stable to pH and heat. Its antibacterial effect is related to the degree of polymerization and the environment. The molecular weight of polylysine is between 3600-4300 which has the best antibacterial activity.