Isolation And Identification Of Lactic Acid Bacteria From DVS Starter And Biochemical Characteristics Of These Bacteria

The lactic acid bacteria can convert the lactose into lactic acid. Yogurt is a product obtained through milk fermentation with a specific yogurt starter culture consisting of a mixture of two species of lactic acid bacteria (LAB), Lactobacillus delbrueckii subs. bulgaricus and Streptococcus thermophilus. DVS starter is a kind of high concentration and standardized frozen or freeze-dried starter culture. It can be directly thrown into the hot-treated milk to ferment. It doesn't need any treatment in advance before fermentation. Now almost all the big dairy corporations use DVS starter to ferment milk. In this paper we isolate and identify strains from EZAL-MY96 starter, we also analysis the biochemical characteristic of EZAL-MY96 starter. So we could select fine strains, it also provides the basic research for developing the dairy market.The lactic acid bacteria were isolated by semi-selective medium, MRS and M17 culture, and were identified by sugar fermentation experiments, RAPD fingerprint and PCR. Three kinds of lactic acid bacteria from DVS were isolated. One is Streptococcus thermophilus, one was Lactobacillus delbrueckii subs, bulgaricus and another was one of unknown Lactobacillus. We got the growth curve of the three bacteria. We also research the acidification, viscosity and aroma mechanism of the three lactic acid bacteria.It shows that sugar fermentation experiment and PCR can isolate the lactic acid bacteria efficiently. The sugar fermentation experiment can identify the two Lactobacillus rapidly. Different DVS strain has different acidification, viscosity and aroma characteristic. This paper provides an important method and experimental data for developing the DVS starter.