Study On Screening And Optimation Of Lactic Acid Bacteria And Charateristics Of The Bacteriocin

This experiment is to obtain a bacteriocin with a strong inhibitory effect and broad-spectrum through isolation and screening of lactic acid bacteria from fermented foods and the physiochemical charaterisitics of the bacteriocin was investigated and optimized the fermentation conditions of the strain, discusses its application in feed. The results as follows.1. Strains with inhibitory effect from the test of 20 lactic acid bacteria isolated by Double agar diffusion method, by which S1-4 was selected because of its significant inhibitory effect. The exhibited inhibitory activity against part of the Gram-positive bacteria and Gram-negative bacteria. And antibacterial spectrum was wide.16S rDNA molecular identification results shown that the S1-4 was Lactobacillus pentosus (similarity of 99.7%).2. The characteristics of antibacterial substances of Lactobacillus pentosus S1-4, were tested for Escherichia coli 3301 as the indicator by the Double agar diffusion method. The results showed that the antibacterial activity of strain S1-4 was not destroyed after treatment with papain, but destroyed after treatment with pepsin and trypsin. This antibacterial substances of Lactobacillus pentosus S1-4 showed good thermal stability and stable antibacterial activity under acidic conditions in pH 3.5-5.5. The inhibitory activity of this strain fermentation supernatant was not affected by some chemical agents and ultraviolet irradiation treatment.3. By single factor experiments and orthogonal experiments, the optimal fermentation condition of antibacterial substance produced by Lactobacillus pentosus S1-4 and antibacterial spectrum of antibacterial compounds was studied. The result showed that the optimum inoculation quantity was 2%, initial fermentation pH was5.5,culturing at 30℃ for 26 hours. The diameter of inhibitory activity of Lactobacillus pentosus under the optimum broth was (30.08 ± 0.69) mm, the optimized bacteriostatic activity increased 1.19 times.4. The purification of the antibacterial substances of Lactobacillus pentosus S1-4 showed that treated with the 60% saturation of the ammonium sulfate precipitation and plastbag.The protein content of the bacteriocin was 4.14mg/mL, the Lactobacillus pentosus under the optimum broth was 38.30 mm.5. The Lactobacillus pentosus S1-4 as the starter cultures in the roughage were tested, the results show that used as a feed natural preservative has good application prospect with good corrosion resistance.