Abstract: In this paper, the isolation and identification of 9 lactic acid Coccus strains from fermented milk were studied. The lactic acid bacteria were isolated by MRS plate streaking cultivation and microscopic examination, and were identified by specific PCR technique. The results of plate streaking cultivation showed that there are 11 strains. The specific PCR primers were designed on the basis of biochemical metabolic enzymes genes coding, different between Lactococcus lactis and Streptococcus thermophilus at the level of strains. The PCR amplifications classify these strains into 9 strains; 6 lactococcus lactis strains, 2 Streptococcus thermophilus strains and 1 Streptococcus agalactiae respectively. In addition, 2 species-specific PCR primers of Lactococcus lactis named LclamyLF-R and LclmapA2F-R respectively were acquired, and Streptococcus thermophilus also had two primers, SttglgPF-R and SttamyLF-R respectively. And even one strain-specific primer of AS1.1936 named LclamyYF-R is obtained.

Key words:  , Lactococcus lactis； Streptococcus thermophilus； PCR(polymase chain reaction)； identification；