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

Abstract

Abstract.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 acidproducing 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.

Isolation and identification of lactic acid bacteria (Lactobacillus plantarum YS2) from yak yogurt and its probiotic properties

“…Usually, the pH of gastric juice in human body is about 3, and the digestion time is between 1-3 h. The viability of each strain was evaluated by lactic acid bacteria digestion in the pH 3 artificial gastric juice for 3 h, and the lactic acid bacteria with good tolerance were screened out [12]. In this study, the tolerance of 4 strains of Lactobacillus in simulated gastric juice was studied.…”

“…The collected bacterial pellet was re-suspended using a sterile saline (5 mL), and following which 1 ml suspension was mixed with 9 mL sterile artificial gastric juice (0.2% NaCl, 0.35% pepsin, pH 3.0) and incubated in a thermostatic oscillator at 37°C and 300 rpm. Subsequently, sample (200 µL) was pipetted well and incubated with a Lactobacillus MRS Agar plate at 37°C for 3 h. After 0 and 3 h later, the number of colony forming units (CFUs) was counted and calculated the bacterial survival rate, the survival in pH 3.0 artificial gastric juice was calculated according to formula: viable count at 3 h (CFU/mL) / viable count at 0 h (CFU/mL) × 100% [12].…”

“…After incubation at 37°C for 24 h, the blank medium was used as control, all the media were determined at 600 nm, and the growth in bile salt was calculated according to formula: bile salt containing culture medium OD600 nm/blank culture medium OD600 nm × 100% [12].…”

“…Then, standing for 5-10 min for layer, take the lower aqueous phase, with PBS buffer fluid as the blank control to test OD560 the value of nm. The hydrophobic rate (A0 and A are nm values of OD560 of bacteria fluid before and after mixing with xylene) are calculated according to the formula: (A0-A)/A0 × 100% [12].…”

Preventive Effects of Lactobacillus Plantarum YS4 on Constipation Induced by Activated Carbon in Mice

“…Then, saline was addedto get 5 mL of the bacterial suspension. It was then mixed with artificial gastric juice at the volume ratio of 1.0 to 9.0;subsequently, it was shaken, followed by culture for 3 h under 37 • C which gave the number of viable LP-YS4 as measured at 0 and 3 h, which helped calculate the tolerating ability of lactic acid bacteria in artificial gastric juice (%) = viable count (CFU/mL)(colony-forming units per milliliter) at 3 h/viable count (CFU/mL) at 0 h × 100% [11].…”