| A lactic acid bacterial strain, Sporolactobacillus S1, was investigated to explore its probiotic activity. The growth property of the strain and its sensitivity to antibiotics were determined. A range of different substrates were screened for beneficially stimulating the growth of lactic acid bacteria (LAB). The effects of daidzein and skimmed milk on the survival of Sporolactobacillus S1 were investigated under different pH and bile salt conditions. To further understand the probiotic role of the strain in the intestine of piglets, an in vivo experiment was also conducted. This thesis includes four sections.In the first section, growth properties of Sporolactobacillus S1 were analyzed by monitoring the development of growth density and pH in the culture during incubation. The results showed that the growth of S1 was rapid. S1 reached its exponential growth phase after 2 h incubation and went into stationary growth phase after 10 h. In stationary phase, the pH value of the culture declined to below 4.5. Sporolactobacillus S1 was also compared with Lactobacillus L7 and E. coli O141 in their sensitivity to antibiotics. The results showed that the mimimal inhibitory concentration (MIC) of most antibiotics on S1 was higher than those on L7 and 0141.In the second section, a range of substrates (0.5% glucose, 0.3% yeast extract, 0.5% sugar-beet dregs, 0.5% corncob and 0.5% citrus peel powder) were screened for their effect on the growth of lactic acid bacteria (LAB). The effect of daidzein at 10, 20 , 50, 100 mg L-1 on the growth of LAB were also analyzed. The results showed that as compared with the control group, the addition with 0.3% yeast extract and 0.5% citrus peel powder improved the growth of LAB and apparently increased their lactic acid production. The growth of the LAB was slightly faster with the addition of 0.5% sugar beet dregs and 0.5% corncob than the control group, but the lactic acid productions were similar. The addition of 0.5% glucose did not enhance the growth of LAB, but increased the lactic acid production after 10 h incubation. However, daidzein showed no significant effect on the growth ofLAB in culture.In the third section, in vitro experiments were conducted to investigate the effects of daidzein and skimmed milk on the survival of Sporolactobacillus S1 under different pH and bile salt conditions. The results showed that under either low pH or bile salt conditions SI survival counts with the addition of 1% skimmed milk were significantly higher than those in the control. As compared with the control, treatment with 50 mg 鈥?L"1 daidzein enhanced the S1 survival counts under bile salt conditions, but decreased the survival counts under low pH conditions.In the fourth section, in order to obtain an ideal preparation of Sporolactobacillus SI for piglets experiment, two preparation forms ( freeze drying powder and freezing liquid ) were compared by enumeration of SI survival counts during processing and preservation. The results indicated that SI in the form of freezing liquid showed higher survival rate than in the form of freeze drying powder. To investigate the effects of Sporolactobacillus SI on E. coli and LAB counts in jejunum and colon of piglets and the fluctuation of VFA concentration in colon of piglets from 7 days of age to 35 days of age. six litters of piglets were divided randomly into two groups, namely the control group and LAB group. The results showed that the counts of E. coli and LAB in jejunum and ileum was stable before weaning. After weaning both the counts of E. coli and that of LAB in jejunum and colon showed apparent decrease, but the decrease of LAB count was more significantly than that of E. coli. As compared with the control group, oral administration with Sporolactobacillus SI enhanced the ratio of the LAB count to the E. coli count in jejunum and colon of piglets after weaning. The VFA concentration in colon of piglets decreased obviously after weaning. Treatment with S1 could apparently increase the VFA concentration in colon of piglets as compared w...
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