The Screening And Antimicrobial Activity Research Of Nisin

The number of Antimicrobial peptides has been found reached2200since1970s and1980s,and a large number of these drugs enter clinical trials has made remarkable effective in practice. At the same time,more varieties of the antimicrobial peptide gene can be attain-ed through transgenic technology into cells,they can get disease-resistant. Synthetic class of antimicrobial peptides has made remarkable achievements in the cow mastitis,diarrhea, classical swine fever and other bacterial diseases.Compared with conventional antibiotics, antimicrobial peptides does not produce resistance and residual non-toxic.So far,more than50countries and regions around the world has been approved Nisin as a food preservative. Recently,China has also formulated the Nisin product of na-tional standards,the condu-cting experimental use of Nisin research has far-reaching sig-nificance.The study of this project to the lactic acid streptococcal strains T0538(isolated from cheese to obtain) as experimental materials and gain a new kind of Nisin,and explore the minimal inhibitory concentration of Nisin, the trypsin inhibitory activity, hemolytic ac-tivity and hemor rha-gic activity and bactericidal mechanism, the results are as follows:1. Obtained the NisinP,and recognized as a new discovery of Nisin.The experimental material has been streptococcus strains T0538(isolated from che-ese),through Sephadex G-25gel filtration chromatography, preparative RP-high-pressure liquid chromatography,ion exchange chromatography and analytical reversed-phase high performance liquid chromatography.We purificate out a new Nisin, NisinP, through the Edelman degradation of NisinP Nisin,the primary structure of evaluations. Search on the net library sequence alignment and determine,after this study included get Nisin,NisinP and ever found in the amino acid sequence Nisin differences,belongs to the newly discovered Nisin.2. Obtained the biological indicators of the new Nisin.We detectedthe minimum inhibitory concentration on the new Nisin,the trypsin inh-ibitory activity, hemolytic activity and hemorrhagic activity.The results showed that:Ni-sinP to gram-positive has very good antibacterial effect,but against gram-negative bacteria did not show that the bacteriostatic effect,in addition to the antimicrobial activity, Nisin, NisinP also has trypsin inhibited activity,it showed a very weak hemolysis activity, but did not detect bleeding activity. 3.The bactericidal mechanism of Nisin has been provedIn order to further clarify NisinP sterilization mechanism,we use S.aureus ATCC25923strains and NisinP after incubation of transmission electron microscope analysis,NisinP bacteria and bacterial surface to form the influence of the structure.The results showed thatrbefore processing S.aureus ATCC25923strains with complete cell wall and cell membrane,and the cellular structure is complete,smooth surface,can observe the complete bacterium hair,cell surface did not appear any damage.Due to internal and proteins and DNA bacteria such as material,they dying liquid contained in combination of heavy metal ion,thus make negative after dying of the bacteria present deep black.After NisinP processing,S.aureus ATCC25923cell membrane destroyed,appear different degree of damage or appear the hole of place,membrane boundaries blurred,and even completely dissolved cell membrane.The cell membrane injury causes the cell to content coming out,the bacteria part or all of rupture,and the phenomenon of diluted with cytoplasm, cytoplasm disintegrated,forms cavity,the contents of a cell to reduce or disappear,cause the cells by dying color becomes shallow.These results demonstrate that NisinP can make S.aureus ATCC25923bacteria somatic cell wall burst or on the cell surface forming hole,content were leaked, eventually leading to tbe bacteria death.