Polylysine refers to several types of lysine homopolymers, which may differ from each other in terms of stereochemistry (D/L; the L form is natural and usually assumed) and link position (α/ε).

[2] Since the late 1980s, ε-polylysine has been approved by the Japanese Ministry of Health, Labour and Welfare as a preservative in food.

[6] ε-Polylysine is used commercially as a food preservative in Japan, Korea and in imported items sold in the United States.

The use of polylysine is common in food applications such as boiled rice, cooked vegetables, soups, noodles and sliced fish (sushi).

[8] Polylysine has a light yellow appearance and is slightly bitter in taste whether in powder or liquid form.

α-Polylysine is commonly used to coat tissue cultureware as an attachment factor which improves cell adherence.

Therefore, modified EPLs have the potential of becoming bifunctional molecules, which can be used either as surfactants or emulsifiers in the encapsulation of water-insoluble drugs or as antimicrobial agents.