Study On Producing Capability And DNA Polymorphism Of The Twelve Lactic Acid Bacteria

Twelve Lactic acid Bacteria had been obtained by the lineation on the selectivity flats, including 7 S.thermophilus strains and 5 L.bulgaricus strains. There shape observed by microscope and the growth status which were cultivated in fermented skim milk were researched. The important producing characters were identified, including the value of life, biomass, acidifying, viscidity, flavour compounds and so on. The total genomic DNA of all the Lactic acid Bacteria was amplified through PCR method with 3 selected primers picked out of 10 arbitrary primers. The analyses based on the RAPD data revealed DNA polymorphism. The results indicated:1. There were some differences between the values of life of Lactic acid Bacteria. The S.thermophilus'value of life was higher than that of the L.bulgaricus',and the value of the former was 0.39~ 0.47 while the later was 0.27 ~0.35.2. The growing rule of the single cell microorganism could be found from the biomass curve of Lactic acid Bacteria.3. There were differences between the values of acidifying of the Lactic acid Bacteria. And the mean value of all the S.thermophilus was higher than that of all the L.bulgaricus in this study.4. The viscosity value of S.thermophilus was better than that of the L.bulgaricus. Those values of S.thermophilus were about from 173 mpa.s to 450 mpa.s while that of L.bulgaricus were about from 481 mpa.s to 724 mpa.s. There were distinctly different among the ability of producing viscosity of the Lactic acid Bacteria in this study.5. The quantity of acetaldehyde and diacetyl production from L.bulgaricus was higher than those from S.thermophilus. And the values of acetaldehyde of L.bulgaricus were about from 15.75 mg/L to 18.60 mg/L while the values of diacetyl of L.bulgaricus were about from 0.46 mg/L to 0.75 mg/L. The values of acetaldehyde of S.thermophilus were about from 5.77 mg/L to 8.53 mg/L while the values of acetaldehyde of S.thermophilus were about from0.27mg/L to 0.60 mg/L.6. The correlation of the producing characters was analyzed in the research. And the value of the titratable acidity had strongly negative correlation to the value of pH. To S.thermophilus, the value of diacetyl had strongly negative correlation to the value of titratable acidity and positive correlation to the value of pH; To L.bulgaricus, the value of viscosity had middling related to the value of titratable acidity, and was strongly negative correlation to the value of pH and the quantity of acetaldehyde. There were also some other relativities among the parameters but the value of the relativities was quite low.7. The total genome DNA of S.thermophilus and L.bulgaricus were amplified through PCR method with 3 selected cingulums, and the quantities of total bands were 10 and 11. There were 6 and 10 polymorphic bands in those bands were acquired; the polymorphic rate was 60% and 90.91% respectively.