Study Of Bacteriocins Produced By LABR-X Of Lactobacillus Plantarum

Bacteriocins produced by certain bacteria are antimicrobial peptides or proteins, in sufficient amounts, these peptides can kill or inhibit bacteria competing for the same ecological niche or the same nutrient pool. Although bacteriocins are produced by many Gram-positive and Gram-negative species, those produced by the LAB are of particular interest to the food industry. To date, the only commercially produced bacteriocins is nisin. While nisin has been found to be extremely effective as an additive to prevent spoilage and increase shelf-life in a number of foods. But its effectiveness has been more variable with respect to other applications. So the new bacteriocins should be attractive to explore.In the paper, 8 clonies of good shape were isolated from sauerkraut fermentation broth, the starting strain mutagenesis LABR of the largest inhibitory strains was selected by the antibacterial test. The LABR was identified as Lactobacillus plantarum by the conventional microbiological identification. The LABR-X of the best antibacterial activity was compound selected by UV and DNS from LABR,the fermentation supernatant by centrifugation and concentrated can inhibit indicator strains strongly excluding inhibitive effect of hydrogen peroxide and organic acid.To optimize mutagenesis strains LABR-X culture conditions, the best culture conditions were determined by orthogonal experiments: the temperature 37℃, the initial pH of culture media 6,the culture starter is 5%(v/v),the volume of liquid is 60%. The period of stable growth of LABR-X from 18 to 26 hours under the culture conditions. The inhibitive activity decreased sharply after treatment with proteinase K and Trypsin, with Ninhydrin and biuret reaction response to positive. The results confirmed that these inhibitory materials were protein, could be classed as bacteriocins.Through the principle of protein extraction and purification, the fermentation product of LABR-X were precipitated by ammonium sulphate, followed by weak acid cation exchange chromatography and Tricine-SDS-PAGE to purification. The molecular weight of elution protein of the best inhibition was 20.1 kDa, the inhibition titer double than nisin. The bacteriocins contain 13 kinds of amino acids and 5 kinds of unknown oligopeptide.We researched on mechanism of antibacterial by optical microscope and scanning electron microscope observation of cell morphology and activity assay of alkaline Phosphatase andβ-galactosidase. The experimental results show the bacteriocins inhibit bacteria by destroying the cell wall and membrane of bacteria.