| Objective: Since the metabolism of lactic acid bacteria own characteristics determine its applied potential and value in food industry, especially it isolated from traditional fermented dairy product with a long history, the better lactic acid bacteria selected by the extensive attention from researchers all over the world. XinJiang has a very special geographic environment and the humanistic conditions which created its rich resources of lactic acid bacteria, while residents of the Aletai have been adopted thousands of years old and followed the traditional method of making fermented milk, the production method is simple, unique flavor products, organization delicate, pure taste, and longer periods of storage at temperatures also ensure that local natural taste and status. Therefore, screening,purification and identification of probiotic Lactococcus from the fermented dairy products in this special environment, studying the optimum fermentation conditions in yogurt production, it has a highly practice signification.Methods: The present study was to investigate and screen the lactic acid bacteria from XinJiang Aletai area herdsmen homemade traditional fermented dairy products. The phylogenetic status of those Lactic acid bacteria were identified based on 16 S rRNA gene sequence.(GTG)5-PCR was used to preform the strains with highly homologous of 16 S rRNA were future investigated. We screened the bacteriocin produced by Lactococcus by Oxford Cup Method, studying the growth characteristics and the resistance of bile and acid, and the optimum fermentation conditions used in yogurt production.Result: In this experiment, isolated and purified the 710 presumptive lactic acid bacteria, in which the rod-strains were accounted for most of the all, the second were coccus. isolated from the samples collected the 262 Lactococcus strains. Using(GTG)5 primers rep-PCR molecular genetics technical study the 24 band forms of Lactococcus strains. Combined with the typical bacteria, the three kinds of Lactococcus were dominant. Isolated Lactococcus strains which have some degree of antagonistic properties by Oxford Cup Method. After exclusion of acid, over interference of the hydrogen peroxide and protein nature determination shows the 8 Lactococcus will inhibit the growth of spoilage bacteria in varying degrees, As an important index for screening probiotic strains, the Lactococcus was able to grow in different bile salt concentration; When the pH was about 6.5, the growth of the strain was the best, and the strain could not grow at pH 1.5. In the production process, the role of yogurt fermentation agent is very important, since it is possible to improve the flavor and sensory yogurt products, improve the nutritional value. Screening the55 Lactococcus strains from the samples.These 8 strains have better fermented properties. Screened two bacteria can be used as starter cultures for yogurt production and sensory evaluation better, they had faster acid production, curd short time, the production of acetaldehyde better. At the meantime these strains have a high viable count in bad conditions.They had a little acidity change during the cold storage period. |
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