Screening And Study Of Antioxidative Lactic Acid Bacteria From Koumiss In Xinjiang

In the present study, traditional fermented Koumiss of Minority in Xinjiang as raw materials, lactic acid bacteria (LAB) were isolated, purified and identified by the tests of morphological characters, physiological and biochemical properties. The lactic acid bacteria with antioxidative activity were selected to study the tolerance property and some antioxidative activity influencing factors. Meanwhile, lactic acid bacteria were tested for16S rDNA homology analysis. The results were as follows:1.28strains of LAB were isolated from a sample which was gathered from places such as Shuixigou, Yili and Nashan(simplified characters:S, Y and N)in Xinjiang. According to the morphological characters, physiological and biochemical properties, all of them were confirmed as Lactobacillus, which were identified as L.paracasei, L.plantarum, L.intestinalis, L.helvericus, L. delbrueckii subsp.lactis, L. casei and L.fermentum.2.The antioxidant capabilities of28strains of live cells, cell-free extracts and extracellular secretions were determined through H2O2tolerance capability, scavenging capabilities of hydroxyl free radical, reducing activities and chelation abilities of ferrous ion. The result showed that the two strains of S3and Yll displayed the excellent antioxidant capabilities among28strains of LAB. The two desired strains showed excellent tolerance in different concentration of H2O2in culture media, they were tolerant to l.Ommol/L hydrogen peroxide solution. Scavenging efficiencies of S3and Yll cell suspension and cell-free extracts were38.1%,25.2%and52.3%,29.7%for hydroxyl free radicals when addition level was1.5mL. The two lactic acid bacterial strains showed good reducing activities, the values of A700nm of the two strains were1.272and1.483. The percentage of chelating ferrous ion capacity were36.62%and43.16%, respectively.3.Studying on the ability of acid-base-tolerance. NaCl-tolerance, temperature-tolerance and bile salt-tolerance showed that6.8were the optimum growth pH of S3and Y11. S3and Y11were tolerant to8%and6%NaCl, respectively.37℃were the optimum growth temperature of the two strains. S3and Y11were tolerant to0.10%and0.50%bile salts, respectively. According to the growth curve and the pH curve of strains showed that strain Y11has a relatively shorter logarithmic growth phase and longer stationary phase than strain S3, so that Y11in favor of ferment quackly.4.The change of antioxidant activity of the two strains were determined in different incubation temperature, different incubation time and different pH. The result showed that S3and Y11reached the maximum antioxidative activity at37℃. When the two strains entered the late logarithmic growth phase, the antioxidative activity were reached the maximum. In18h, scavenging of hydroxyl free radical efficiencies of S3cell suspension and cell-free extracts were36.5%and27.8%, reducing activities of extracellular secretions reached the maximum activity, in12h, scavenging of hydroxyl free radical efficiencies of Y11cell suspension and cell-free extracts were32.7%and26.2%, reducing activities of extracellular secretions reached the maximum activity, the two strains had a capacity of chelation abilities of ferrous ion in18h. When the pH was7, the antioxidative activity of the two strains were maximum, scavenging efficiencies of S3and Y11cell suspension and cell-free extracts were37.2%,25.9%and38.6%,29.3%, respectively for hydroxyl free radicals, the two strains had a capacity of reducing activities of extracellular secretions and chelation abilities of ferrous ion when the pH was7.5.7representative strains S3, Y11, Nl, N6, Y2, N2and Y3were tested for16S rDNA homology analysis. It was shown that there was a100%homology between the strain of S3and Lactobacillus paracasei subsp. paracasei strain X208; there was a100%homology between the strain of Y11and Lactobacillus plant arum strain bh6.