Analysis of the diversity and fermentation characteristics of lactic acid bacteria in traditional yogurts from Ta Cheng, Xinjiang

In this experiment, 30 lactic acid bacterias with fast acid-producting capacity were screened from the traditional yogurt of Tacheng in Xinjiang by observing the p H of the fermentation broth and the discoloration time of bromocresol purple plate.Identified them in different ways, for example, morphological characteristics, physiological and biochemical identification, rep-PCR genotyping, 16 S r DNA gene sequence analysis and so on, and furtherly analysised the relationship between the acid production characteristics and protease activity and autolysis rates of different kinds of lactic acid bacteria.The results showed that there were 12 strains of Lactobacillus plantarum, 9 strains of Enterococcus hirae, 3 strains of Enterococcus durans, 2 strains of Lactobacillus fermentum and Enterococcus faecium respectively, 1 strain of Pediococcus acidilactici and Enterococcus faecalis respectively.It was worth mentioning that all of 7 kinds of lactic acid bacteria could normally grow in the milk and reduce the p H of milk, the protease activity was between 3 and 14 U, the autolysis rates was between 3% and 29%, and there was a close relationship between the fermentation characteristics and the species of strains.