The Identification Of Plantaricin And Its Inhibition Against Listeria Monocytogenes In The Food

In the current food antisepsis technology,it has moved from traditional chemical anti-corrosion towards a more natural security biological preservatives.Because of its biodegradation security,bacteriocin has been used as a kind of natural safe food preservatives and got great attention.My research was focused on the antibacterial activity and application of the bacteriocin produced by Lactobacillus plantarum Zhang-LL to provide the theoretical basis on application in the field of food preservation.The main contents are as follows:(1)Identification of bacteriocin-producing strain:Strain Zhang-LL was identified as Lactobacillus plantarum subsp.plantarum by combining morphology with 16S rDNA and pheS gene sequence analysis.And eliminating organic acid and hydrogen peroxide,the antimicrobial substance was confirmed as bacteriocin analyzed by cup-plate method.(2)Separation and purification of the plantaricin:The plantaricin was preliminary extracted by the adsorption-desorption method depended on pH,and purified by ion exchange chromatograph.After purifying,the activity of the plantaricin reached 9.38×103 AU· mg-1.And the plantaricin was purified 32.49 times compared to the fermentation supernatant.Combined with dialysis,Tricine-SDS-page electrophoresis and active glue bacteriostatic test to determine the molecular weight of the plantaricin in 3.5～4.6kda.(3)Physicochemical and biological properties of the plantaricin:The plantaricin could resist high temperature to 100℃ for 90min and keep stable antimicrobial activity at pH from 2 to 8.The plantaricin production reached its maximum at the early stationary phase of the actic acid bacteria and the best harvesting time was 16h.Besides,it covered broad antimicrobial spectrum,especially exhibited strong antibacterial activity against Gram-positive bacterium such as Listeria monocytogenes,Bacillus subtilis,Enterococcus faecalis and Gram-negative bacterium such as Escherichia coli,Salmonella and Enterobacter sakazakii.also it could inhibited the growth of the fungus identified as Trichocomaceae in the strawberry.(4)Antimicrobial application of the plantaricin and its composite antibacterial agent in the food:The reserch was on the effect of the plantaricin and Nisin to inhibit the growth of Listeria monocytogenes in the medium system.Then determined the best antibacterial activity of the combination of the two bacteriocin was P:N(3:1).The composite antibacterial agent of the plantaricin and Nisin was applied in the pork.The application experiment showed that the combination has an increased bactericidal effect against Listeria monocytogenes from day 4 to day 10,causing a reduction of 4.14 log units compared to the control.