Preparation And Antibacterial Activity Of ε-polylysine And Its Composites

Microbe is the major cause of food spoilage and almost all kinds of bacteriawould induce food spoilage under certain conditions. Therefore, it is important andnecessary to develop new technology for spoilage microorganism identification andfood preservation to reduce food corruption.First of all, from spoiled meat products, six kinds of spoilage bacteria wereisolated and three isolates were identified as Bacillus by matrix-assisted laserdesorption/ionization time-off light mass spectrometry (MALDI-TOF MS). Three ofthem were identified as Bacillus at the species level. Further investigated by16SrRNA gene sequencing method, they were confirmed to be Bacillus licheniformis. Itwas difficult to identify the other three isolates, due to the shortage of referencestrains in MALDI-TOF MS. While they were identified as Bacillus subtilis by16SrDNA sequencing method. The identification precision of MALDI-TOF MS wasproved by comparing the two techniques. Providing the database is perfected, it isanticipated to play a role in food microbe identification. On this basis, the inhibitoryeffects of bio-preservatives (Nisin and ε-poly-L-lysine), and chemical preservatives(potassium sorbate and sodium nitrite) against the six newly isolated bacteria werecontrasted. Their inhibitory abilities were ranked as: ε-poly-L-lysine>NISIN>potassium sorbate> sodium nitrite. It was found that chemical preservatives showedno bacteriostatic effect against these food spoilage strains; however, ε-poly-L-lysinewas highly resistant to them. As an excellent bio-preservertive, the dosage ofε-poly-L-lysine can be controlled by combined usage of other preservatives.Secondary, the applications of ε-poly-L-lysine were tried to explord on the fieldsof food, biology, medical materials. Taking advantage of its food-grade-safeantibacterial activity, ε-polylysine/PVA blended membranes and ε-polylysine/PVAfibers were prepared. The composite membranes and fibers had outstandingantibacterial activity and bio-safety. Among them, the ε-polylysine/PVA blendedmembrane prepared by casting was more successful. Visualized under SEM, smoothsurface and homogeneous morphology were observed. It was known from FTIRspectrum that there were no new compounds generated during its fabrication, whichguaranteed its safety. The mechanical properties, such as tensile strength(28.60-33.11MP), were superior to the most antibacterial PVA membranesreported in literatures. The addition of ε-polylysine made the ε-polylysine/PVA filmcould absorb more UV（35%） than the PVA film, while maintain the equal lighttransmittance. Moreover, ε-polylysine/PVA film was more thermal-stable and itswater uptake capability was reduced, in comparision with neat PVA membrane.In the same time, we tried to modify the surface of SiO2nanoparticles by usingε-polylysine to enhance their DNA adsorption capacity.