Preservative Effect Of ε-polylysine And Its Antibacterial Mechanism Against Escherichia Coli

The prospect of ε-Polylysine (ε-PL) in food preservation industry was verybroad, due to the natural, safe, healthy, nutrient and remarkable antibacterialcharacteristics of ε-PL. In this study, the basic properties and progress of ε-PL wereintroduced briefly and the effects of ε-PL on physicochemical as well as microbialfeatures of chilled meat were researched. Additionally, this paper investigated theeffects of ε-PL on cell wall, cell membrane and cell contents to reveal antibacterialmechanism of ε-PL against Escherichia coli (E.coli) at the molecular level. And theseresults were obtained as follows:(1) The change of sensory properties (appearance, odor, texture, taste andoverall acceptability) of chilled meat before and after treated with differentconcentrations ε-PL showed that ε-PL could improve sensory properties and extendshelf life of chilled meat. Furthermore, with the increase of ε-PL concentration, time ofmaintaining well sensory properties of chilled meat was increased. ANOVAdemonstrated that there were no differences between1.25and1.50%ε-PL in sensoryproperties of chilled meat. Thus, in order to minimize the content of additives in food,1.25%ε-PL was optimal concentration for using in chilled meat with6days of shelflife.(2) The application of ε-PL on chilled meat resulted in significant effects ofTBC, pH, TVB-N, and MetMb with increasing concentrations of ε-PL when comparedto control. However, ε-PL did not affect TBA of chilled meat. These results revealedthat1.25and1.50%ε-PL could inhibit notably the growth and reproduction ofmicroorganisms, decrease the decomposition of meat protein, and prevent the change ofcolor of chilled meat. Therefore, ε-PL had the potential to be used as nature preservativeand to extend the shelf life of chilled meat.(3) The effects of different concentrations of ε-PL on cell wall, cell surfacehydrophobicity, cell outer membrane permeability, cell membrane permeability and cellmembrane proteins of E.coli showed that ε-PL could change E.coli cell membranestructure, increase permeability of cell wall, increase cell surface hydrophobicity,increase outer membrane and cell membrane permeability, disrupt cell membraneprotein structure, and cause the leakage or hinder the synthesis of membrane protein,leading to interference of cell normal physiological activities and damaging normal cellmorphology. Therefore, growth of E.coli was inhibited and even death, in addition, the impacts increased with increasing ε-PL concentrations.(4) The effects of ε-PL on respiratory chain dehydrogenase, β-galactosidase,metal ion, protein and nucleic acid in E.coli cells indicated that ε-PL could damage thenormal structure of E.coli cells, cause the leakage of β-galactosidase, Ca2+, K+, Mg2+,degrade the cell protein, interfere with the normal synthesis of protein, DNA, lead toprotein aggregation, inhibit the activity of respiratory chain dehydrogenase, damagecells DNA instructure, and cause the leakage of DNA, RNA in E.coli cells. Besides, theinfluence increased with increasing concentration of ε-PL, eventually inhibiting thenormal growth of E. coli, or even killing bacteria.