Optimization On Fermentation Conditions Of Bacteriocin Production By Lactobacillus Plantarum And Separation & Application Of The Bacterioncin

Development of bacteriocin had become an important topic, since Nisin production by Lactococcus lactis was licensed as preservative. Bacteriocin could be considered as peptides of inhibitory activity producted by microorganism synthesis through ribosome. Nonhazardous effect is an advantage of bio-preservatives. Bacterocins production of LAB implied an important biological role. Although bacteriocin was produced in industry, some of them couldn't inhibition Gram-negative bacteria. Its effectiveness has been more restrict to other applications. So the new bacteriocin should be attractive to explore. Lactobacillus plantarum KLDS1.0391, a bacteriocin-producing strain, was screened from 67 strains of lactobacilli from different sources. The bacteriocin production by this strain exhibited a broad spectrum of antagonistic activity against various species of Gram-positive bacteria, Gram-negative bacteria. Therefore, the purpose of this subject is optimizating fermentation conditions of bacteriocin production by Lactobacillus plantarum KLDS1.0.391 using response surface methodology, obtaining Plantaricin MG of inhibitory activity by spray-drying. Application of Plantaricin MG could offer conditions for development.Skim milk, soy whey, cheese whey, corn steep liquor was used as medium for Lactobacillus plantarum KLDS1.0391. The effect of medium on bacteriocin production by this strain was studied. The peptide distribution of skim milk of different degrees of hydrolysis was analyzed by capillary electrophoresis and SDS-PAGE. Results indicated that casein was completely hydrolyzed and whey was partly hydrolyzed in skim milk with DH of 15%. The peptide of low molecular weight after hydrolyzing was favored by Lactobacillus plantarum KLDS1.0391. Skim milk with DH of 15% was the suitable medium.Based on the single factor experiment, the effect of fermentation pH, inoculum size and fermentation temperature on bacteriocin were optimized by response surface methodology. Results indicated that the optimal fermentation conditions were as follows: fermentation pH 5.1, inoculum size 1%, fermentation temperature 33℃. Under these optimum conditions, the maximal antibacterial activity was increased by 42.96%, achieved 601.32 IU/mL.Fermentation broth was ultrafiltrated by membrane of MW 1KDa. The raffinate was ultrafiltrated by membrane of MW 3KDa. The ultrafiltrate was condensed by rotary evaporation. Plantaricin MG was obtained by spray-drying. The antibacterial activity achieved 2000.56 IU/g. Effect of Plantaricin MG on yeast in yoghurt was studied. Results showed that for samples of yoghurt with polluted yeasts of initial concentration 1 CFU/mL, Plantaricin MG had inhibited yeast completely. Samples of yoghurt with polluted yeasts of initial concentration 10 CFU/mL and 100 CFU/mL, Plantaricin MG had a weak bacteriostatic action, compared with bacteriostatic action of natamycin.Effect of Plantaricin MG on Listeria monocytogene in cooked ham was studied. Results showed that combination of Nisin, Plantaricin MG and Lactobacillus plantarum had improved inhibitory effect than them respectively with significant differences.Effect of Plantaricin MG on refreshing in fresh pork was studied. Results showed that fresh pork could preserve 6 d. Sample of fresh pork with Plantaricin MG could preserve 9 d. Combination of Plantaricin MG and 2% sodium lactate was added, the pork could be preserved 12 d.