Screening and identification of lactic acid bacteria strains with high acid-producing from traditional fermented yak yogurt

A total of 57 strains of lactic acid bacteria (LAB) were isolated and purified from traditional fermented Yak Yogurt in Hongyuan-Sichuan and Yangbajing-Tibet. The strains with high acid-produced were screened by soluble calcium circle and titratable acidity determination. The five strains, 7-1, 22-1, 28-1, 34-1 and 62-1, possessed the high acid-producing and the value of titratable acidity is 196.2, 191.1, 192.2, 194.8 and 200.2 T respectively. Based on 16S rDNA sequence analysis, 22-1 was identified as Lactococcus lactis subsp. lactis , 28-1 as Lactobacillus casei , 34-1 as Lactobacillus fermentium , 7-1 and 62-1 as Enterococcus durans . This study could provide the evidence for researching fermentation strains to improve yogurt quality.