Abstract: The aims of this study were to explore the diversity of lactic acid bacteria (LAB) in traditional fermented milk in western China and to analyze the nitrite degradation capability of the dominant strains in order to provide useful data for their industrial application. The LAB isolates, isolated from different fermented milk products from different pastoral areas, were identified by 16S rDNA sequence analysis, and their nitrite degradation capabilities were comparatively determined by colorimetry. The results obtained showed that: 1) A total of 275 LAB strains were isolated from 104 fermented milk samples, belonging to 23 species in 6 genera. Lactobacillus helveticus was detected from the samples from Qinghai, Gansu, Xinjiang, Inner Mongolia and Tibet. Meanwhile, L. helveticus and L. plantarum were isolated from fermented yak milk, koumiss, shubat and milk dreg. 2) The nitrite degradation rates?of 275 LAB isolates were between 4.8% and 99.9%, 50% of which had good nitrite degradation capability with an average of over 91.3%. 3) The nitrite degradation capability of these LAB isolates varied depending on the sources and species. The effect of LAB from Tibetan was significantly higher than that of LAB from Qinghai, Gansu and Xinjiang (P < 0.05), and the effect of LAB from milk dreg was significantly higher than that of LAB from fermented yak milk and koumiss (P < 0.05). L. plantarum, L. paracasei and L. breris could stably and efficiently degrade nitrite, and L. plantarum had the strongest nitrite degradation ability among the 8 dominant strains. However, a significant difference in the nitrite degradation ability was found among some dominant strains (P < 0.05).

Key words: lactic acid bacteria, isolation and identi?cation, nitrite, degradation rate