Screening Of Board Spectrum Bacteriocin-producing Lactic Acid Bacteria And Characteristic And Fermentation Condition Optimization Of Bacteriocin

Thirty lactic acid bacteria strains were screened from kimchi, pickled cabbage,sauerkraut, cheese, yoghourt. Escherichia coli and Staphylococcus aureus were selected asthe indicative strain. Lactic acid bacteria A8isolated from kimchi showed obviousantibacterial activity by antibacterial test, the test of eliminating organic acids and hydrogenperoxide, and the effect of protease. The inhibitory material produced by this strain could notonly inhibit gram-positive bacteria but aslo gram-negative bacteria, and it was a broadspectrum bacteriocin. And its biological property and fermentation condition were studied tosupply a theoretical guide for developing and applying of new lactolin in food industry.There are three main parts in this study:1. By using double agar diffusion method,30lactic acid bacteria strains were screenedfrom kimchi, pickled cabbage, et al. Escherichia coli and Staphylococcus aureus wereselected as the indicative strain,8lactic acid bacteria strains showed broad antimicrobialactivity by preliminary screening, Lactic acid bacteria A8isolated from kimchi showed obviousantibacterial activity by the second screening. The antibacterial circle diameter of Lactic acidbacteria A8was20.2mm and18.3mm for two indicative strains respectively. After thefermentation supernatant of Lactic acid bacteria A8was treated with trypsin and papain, itsinhibition activity was lost, which indicated that bacteriocin of Lactic acid bacteria A8belonged to protein. Lactic acid bacteria A8was identified as Lactobacillus plantarum bycolony characteristics, individual form and physiological-biochemical characteristics.2. The biological features of bacteriocin from Lactobacillus plantarum A8were asfollows. It was stable in acid conditions and high temperature and sensitive to proteinase.EDTA can enhance the inhibitory activity of bacteriocin, and the antibacterial circle diameterof bacteriocin was24.3mm. However, its inhibitory activity was not affected by Tween80,SDS, NaCl, Triton X-100and Triton X-114. The bacteirocin has a broad spectrum. Its actionmode is bactericidal way.3. The fermentation condition for bacteriocin production of Lactobacillus plantarum A8 optimized by single factor experiment and orthogonal experiment. The optimum culturemedium coponents was peptone14.0g/L, beef extract14.0g/L, yeast extract7.0g/L, K2HPO42.0g/L, ammonium citrate dibasic2.0g/L, sodium acetate5.0g/L, sucrose35.0g/L, Tween804.0mL/L, MgSO4·7H2O0.58g/L, MnSO4·4H2O0.25g/L. The optimum incubation temperaturewas30℃, the optimumincubation time was36h, the optimum broth initial pH was6.5. Whencultured under the fermentation conditons, antibacterial circle diameter of bacteriocin was20.6mm for Staphylococcus aureus.