Dynamic changes of the microbial communities during the preparation of traditional Tibetan Qula cheese

The production of traditional Tibetan Qula cheese involves a natural fermentation by microorganisms. As a result, there are complex changes in microbial communities during Qula production from raw yak milk. In this study, microbial changes during Qula production were studied, including those of lactic acid bacteria (LAB), coliform bacteria, aerobic bacteria, mycelial fungi, and yeast. Isolated LAB strains were identified by physiological, biochemical, and 16S ribosomal RNA (rRNA) gene sequence analyses. LAB, coliform bacteria, aerobic bacteria, mycelial fungi, and yeast were present throughout the Qula production at different levels. The following LAB species were involved in the fermentation process, Leuconostoc mesenteroides, Enterococcus hirae, Enterococcus mundtii, Lactococcus lactis, Lactobacillus plantarum, Lactobacillus sakei, Lactobacillus buchneri, Lactobacillus diolivorans, and Lactobacillus casei. During the course of preparation, Ln. mesenteroides was the predominant species.