Screening of Probiotic Activities of Lactobacilli Strains Isolated from Traditional Tibetan Qula, A Raw Yak Milk Cheese

Abstract

In this study, 69 lactobacilli isolated from Tibetan Qula, a raw yak milk cheese, were screened for their potential use as probiotics. The isolates were tested in terms of: Their ability to survive at pH 2.0, pH 3.0, and in the presence of 0.3% bile salts; tolerance of simulated gastric and intestinal juices; antimicrobial activity; sensitivity against 11 specific antibiotics; and their cell surface hydrophobicity. The results show that out of the 69 strains, 29 strains (42%) had survival rates above 90% after 2 h of incubation at pH values of 2.0 or 3.0. Of these 29 strains, 21 strains showed a tolerance for 0.3% bile salt. Incubation of these 21 isolates in simulated gastrointestinal fluid for 3 h revealed survival rates above 90%; the survival rate for 20 of these isolates remained above 90% after 4 h of incubation in simulated intestinal fluid. The viable counts of bacteria after incubation in simulated gastric fluid for 3 h and simulated intestinal fluid for 4 h were both significantly different compared with the counts at 0 h (p<0.001). Further screening performed on the above 20 isolates indicated that all 20 lactobacilli strains exhibited inhibitory activity against Micrococcus luteus ATCC 4698, Bacillus subtilis ATCC 6633, Listeria monocytogenes ATCC 19115, and Salmonella enterica ATCC 43971. Moreover, all of the strains were resistant to vancomycin and streptomycin. Of the 20 strains, three were resistant to all 11 elected antibiotics (ciprofloxacin, erythromycin, tetracycline, penicillin G, ampicillin, streptomycin, polymyxin B, vancomycin, chloramphenicol, rifampicin, and gentamicin) in this study, and five were sensitive to more than half of the antibiotics. Additionally, the cell surface hydrophobicity of seven of the 20 lactobacilli strains was above 70%, including strains Lactobacillus casei 1,133 (92%), Lactobacillus plantarum 1086-1 (82%), Lactobacillus casei 1089 (81%), Lactobacillus casei 1138 (79%), Lactobacillus buchneri 1059 (78%), Lactobacillus plantarum1141 (75%), and Lactobacillus plantarum 1197 (71%). Together, these results suggest that these seven strains are good probiotic candidates, and that tolerance against bile acid, simulated gastric and intestinal juices, antimicrobial activity, antibiotic resistance, and cell surface hydrophobicity could be adopted for preliminary screening of potentially probiotic lactobacilli.

Identification of salt tolerance-related genes of Lactobacillus plantarum D31 and T9 strains by genomic analysis

“…The cell suspension of L. plantarum D31 and T9 strains was individually inoculated into the MRS broth containing different concentrations of bile salt (0.0%, 0.05%, 0.1%, 0.2%, and 0.3%) (Beijing Land Bridge Technology, Beijing, China) and incubated at 37°C for 24 h. Growth curves of these two strains at different acid, osmotic pressure, and bile salt conditions were individually determined as described above. Tolerance of L. plantarum D31 and T9 strains to artificial gastric and intestinal fluids was determined according to the method described previously (Zhang et al 2016) with slight modification. The cell suspension of L. plantarum D31 and T9 strains was individually inoculated (10%, v/v) into the artificial gastric and intestinal fluids and incubated at 37°C for 180 min and 240 min, respectively.…”

“…The cell suspension of L. plantarum D31 and T9 strains was individually inoculated (10%, v/v) into the artificial gastric and intestinal fluids and incubated at 37°C for 180 min and 240 min, respectively. The viable cell count assay was performed as described previously (Zhang et al 2016). Artificial gastric fluid contained 0.35% pepsin and 0.2% NaCl in 100 ml of distilled water.…”

In vitro evaluation of probiotic properties of lactic acid bacteria isolated from some traditionally fermented Ethiopian food products

“…tolerans strain NBRC 15906 ( Fig.). According to Shokryazdan,Sieo (45), the results of comparative 16S rRNA gene analysis 23 showed LAB isolates belonged to L. acidophilus, L. fermentum, L. buchneri and L. casei. In addition, Cho, Lee (46) have identified Lactobacillus strains with potential probiotic properties from the feces of breast-feeding piglets using 16S rRNA genes analysis.…”

Evaluation of Enterococcus faecium Ch-1 isolated from Chuli- A traditional fermented apricot product of Trans Himalayan region

“…This isolate has been reported for the very first time from chuli with an exceptionally high probiotic potential. [24,30,31] . But in the present study, all the six screened isolates were found sensitive to protein inhibitors.…”

“…Thus, the tolerance was assayed by determining the viable count in simulated gastric juice after the incubation for different time intervals up to 4 hour. All the experiments were carried out in triplicates [24] .…”