Polylysine - Natural Preservative in Food Products

Polylysine
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. 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.


Properties
ε-Polylysine is a natural substance made from streptomyces albulus metabolism. High potency ε -Polylysine is a hygroscopic, light yellow power. It is soluble in water, slightly soluble in ethanol, insoluble in organic solvent such as ethyl acetate, ether, etc.. The molecular of ε -Polylysine is a straight chain polymer of lysine. It can decompose to lysine in human body, and can be completely digested and absorpted , but has no poisnous side-effects.

ε-Polylysine can inhibit the growth of Gram(+) and Gram(-) bacteria , yeast, mould, virus, ect., especially inhibit the Gram(-) bacteria which can't be easily inhibited by other preservatives,such as E coli, Salmonella,and thermophilic bacillus , etc. Its activity is not affected by PH value , and stable when heated (120°C for 20min). It is widelly used as a highly efficient and safe food preservative.



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.


History
The production of ε-polylysine by natural fermentation was first described by Japanese researchers Shoji Shima and Heiichi Sakai in 1977.


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.


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).


Literature studies have reported an antimicrobial effect of ε-polylysine against yeast, fungi, gram-positive bacteria and gram-negative bacteria


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


Polylysine was generally recognized as a safe food preservative by FDA in October,2003. It is widely used in food industry. In food application, it is usually applied with alcohol, organic acids, or glyceride, etc.. It can be used in cooked rice, cakes, snacks, noodles, drinks, brewing, meat products, canned food, etc. Recommend dosage from 35 to150 ppm for food processing.

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. Polylysine is “Generally Recognized As Safe” (GRAS) by the FDA.


References
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Last updated on Wednesday May 28, 2008 at 00:55:42 PDT (GMT -0700)

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