ε-Polylysine can greatly inhibit the growth of bacteria, yeasts and moulds bacteria, especially to the Gram+ bacteria which can’t easily inhibit by others. As a good preservative, ε-PL is characterized as being high safety, water-soluble, stable at high temperatures, widely usage, non prejudice to the taste, antibacterial in neutral or subacidity conditions. Because of the stability at high temperatures, it can inhibit some heat-resistant bacillus after heat treatment and sometadpole-form no contractile siphovirus bacteriophage as well.

Antibacterial Spectrum

Table 1 ε-PL MIC Test (minimum inhibition concentration)

As can be seen, ε-PL has wide range of antimicrobial spectrum with minimum inhibitory concentration of bacteria less than **0μg/ml, and to Fungi, the MIC is higher.

Antibacterial Mechanism

ε-PL is in high aggregation state of multivalent cations, which can damage the cell membrane structure of microorganisms, causing cell material, energy and information transmission interrupted. Its combination with the ribosomes within the cell affects the synthesis of biological macromolecules, eventually leading to cell death.

Safety

It had been approved by FDA for use as an antimicrobial agent in cooked rice or sushi rice at levels up to *0 milligrams per kilogram (mg/kg) of rice. The results of an acute toxicity study and bacterial assays for mutagenicity show that ε-Polylysine was non-toxic and there was no evidence for mutagenic activity of ε-Polylysine. So ε-Polylysine is absolutely safe to be used as food preservative.

Range of Application

With features of solubility in water, good heat tolerance and extensive antimicrobial against fungi, ε- PL can be used under various conditions. A test for thermal stability and pH test using scope of ε-PL was carried out and the results are shown in Table 2 and Table 3

Table*2 Effect of temperature on the Minimum Inhibition Concentration (MIC) of ε-Polylysine against Growth of Escherichia coil

Table 3 PH on ε-PL MIC

No Influence on Food Flavor

As a food preservative, ε-PL does not affect food flavor. When added to food, ε-PL and dextran will have Maillard reaction after high temperature disinfecting because of its excellent

heat-resistance property. Not only can it maintain the effectiveness of antimicrobial, but also it has strong emulsifying properties, which is unacted whether the food is under circumstances of PH7 or 1 mol/L NaCl. Therefore, ε-PL as food additive has a dual function of emulsificationand fresh-keeping.