Medium Optimization, Probiotic Properties Of Pediococcus Acidilactici And Application As Preservative In Pork

Pediococcus acidilactici PA003produces pediocin which has the antimicrobialactivity against Listeria mononucleosis and other Gram-positive bacteria. This studyis aimed at researching the optimization of culture medium and fermentationconditions, the probiotic properties of Pediococcus acidilactici PA003，and theapplication as preservative in pork.In order to obtain a low-cost fermentation medium for Pediococcus acidilacticiPA003in a large scale, the culture medium and fermentation conditions wereoptimized by Single Factor Test and Orthogonal Test. The results showed that the bestcompositions of fermentation medium were2%of molasses,2%of soybean powder,0.3%of corn extraction solution,0.2%of dipotassium hydrogen phosphate,0.5%ofsodium acetate,0.2%of ammonium citrate,0.058%of magnesium sulfate,0.025%ofmanganese sulfate, and0.1%of Tween80, and the pH of the medium was6.5. Theresults also indicated that the best fermentation inoculum size was6%, incubationtemperature at37℃and time for14h, speed at140r/min. The biomass of Pediococcusacidilactici in such conditions reached6.4×109CFU/mL, which was equivalent to thebiomass in MRS medium.The probiotic properties of Pediococcus acidilactici PA003were studied bytesting its inhibition activity and the tolerance to high temperature, acid, bile salt andantibiotics. The results showed that the strain was able to inhibit the growth ofListeria mononucleosis and so on. It was resistant to the temperature of50℃, but thesurvival rate declined at80℃and above. The number of bacteria reduced from108CFU/mL to106CFU/mL after6h treatment in MRS culture of pH2.5, whereas itshowed increasing trend if treated with the culture of pH3.5and4.5for4h. The strainwas proved to have better tolerance to the bile salt concentration of0.1%～0.4%, butgrew worse if it was above0.4%. The strain also indicated strong tolerance toantibiotics such as Norfloxacin, Gentamicin, Tetracycline, Penicillin and Rifampin.The Pediococcus acidilactici strains were mixed with indicators Listeriamononucleosis and Escherichia coli respectively，and seeded to pork samples. Theseeded samples were stored at4℃and20℃for a week and the change of indicatorswere observed. The results indicated that Pediococcus acidilactici had the antimicrobial activities against both seeded Listeria mononucleosis and Escherichiacoli. Althouth the number of Listeria mononucleosis rebounded on the seventh day,the number of Listeria mononucleosis was still less than that of controlled samples.The medium with good industrial prospect for the culture of Pediococcusacidilactici was established. The probiotic properties of the strain，and the inhibitoryeffect as preservative in pork were explained. The study provided an important basefor Pediococcus acidilactici as probiotics and preservative in food industry.