The epsilon-Polylysine is a small natural homopolymer of the essential amino acid L-lysine that the formula is (C₆H₁₂N₂O)_n. With the CAS registry number 28211-04-3, it is also named as (S)-Poly(imino(2-amino-1-oxo-1,6-hexanediyl)). It is produced by bacterial fermentation.

The epsilon-Polylysine is a homo-polypeptide of approximately 25 ~ 30 L-lysine residues. Epsilon refers to the linkage of the lysine molecules. It belongs to the group of cationic polymers. According to research, ε-polylysine is adsorbed electrostatically to the cell surface of the bacteria, followed by a stripping of the outer membrane. This eventually leads to the abnormal distribution of the cytoplasm causing damage to the bacterial cell.

Uses of epsilon-Polylysine: It is used as a natural preservative in food products in Japan, the republic of Korea and in the USA. It is also used in boiled rice, cooked vegetables, soups, noodles and sliced fish (sushi). In addition, this chemical is used to coat tissue cultureware as an attachment factor which improves cell adherency.