Polylysine

Chembox new
Name = Polylysine
ImageFile = polylysine.jpg
ImageSize = 160px
ImageNameL1 = Skeletal formula of polylysine
IUPACName = Poly [imino [(2S)-2-amino-1-oxo-1,6-hexanediyl]
Section1 = Chembox Identifiers
CASOther = 28211-04-3
Section2 = Chembox Properties
Formula = C₁₈₀H₃₆₂N₆₀O₃₁
MolarMass = 4700 g/mol (degree of polymerization = 30)
MeltingPt = 172.8 °C (446.0 K, 343.0 °F)
Solubility in water = Soluble
pKa = 9

Polylysine (ε-Poly-L-lysine)is a small polypeptide of the essential amino acid L-Lysine that is produced by bacterial fermentation. ε-Poly-L-lysine is used as a natural preservative in food products (see also: Polylysine in food).

Chemical structure & function

ε-Polylysine is a homo-polypeptide of approximately 25 ~ 30 L-Lysine residues [Shima, S. and Sakai H., 1977, Polylysine produced by Streptomyces, Agricultural and Biological Chemistry, 41, pp 1807-1809] . Epsilon (ε) refers to the linkage of the lysine molecules. In contrast to normal peptide bond that is linked by the alpha-carbon group, the lysine amino acids are molecularly linked by the epsilon amino group and the alpha carboxyl group.

ε-Polylysine belongs to the group of cationic surfactants. In water, ε-polylysine contains a positively charged hydrophilic (amino) group and a hydrophobic (methylene) group. Cationic surface-active compounds have the ability to inhibit the growth of microorganisms. According to Japanese researchers, ε-polylysine is absorbed 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 [Shima, S. et al, 1984, Antimicrobial action of ε-poly-L-lysine, The Journal of Antibiotics, 37, pp 1449 - 1455] .

Production

Production of polylysine by natural fermentation is only observed in Streptomyces strains. The strain Streptomyces albulus is most often found in literature studies and is also used for the commercial production of ε-polylysine [ [http://www.chisso.co.jp/yokohama/english/reseach/polylysine/index.html] Chisso website: Industrial producer of polylysine ] .

History

The production of ε-polylysine by natural fermentation was first described by Japanese researchers Shoji Shima and Heiichi Sakai in 1977 [Shima, S. and Sakai H., 1977, Polylysine produced by Streptomyces, Agricultural and Biological Chemistry, 41, pp 1807-1809] .

Since the late 1980’s, polylysine has been approved by the Japanese “Ministry of Health, Labour and Welfare” as a preservative in food. In January 2004, polylysine became GRAS (Generally Recognized As Safe) certified in the United States [GRAS Notice No. GRN 000135 [http://www.cfsan.fda.gov/~rdb/opa-g135.html] ] .

Polylysine in food

Polylysine is commercially used as a food preservative in Japan, the republic of Korea and in the USA. Food products containing polylysine are mainly found in Japan. The use of polylysine is common in food applications like: boiled rice, cooked vegetables, soups, noodles and sliced fish (sushi) [Hiraki, J. et al, 2003, Use of ADME studies to confirm the safety of ε-polylysine as a preservative in food, Regulatory Toxicology and Pharmacology, 37, pp 328-340] .

Literature studies have reported an antimicrobial effect of ε-polylysine against yeast, fungi, gram-positive bacteria and gram-negative bacteria [Hiraki, J., 1995, Basic and applied studies on ε-polylysine, Journal of Antibacterial Antifungal Agents, 23, pp 349-354]

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

Biology and Health effects

ε-Polylysine was found to be non-toxic at high levels in acute animal studies and was not mutagenic in bacterial reversion assays [Hiraki, J. et al, 2003, Use of ADME studies to confirm the safety of ε-polylysine as a preservative in food, Regulatory Toxicology and Pharmacology, 37, pp 328-340] . Polylysine is “Generally Recognized As Safe” (GRAS) by the FDA [GRAS Notice No. GRN 000135 [http://www.cfsan.fda.gov/~rdb/opa-g135.html] ] .

References