Study of growth kinetic and gastrointestinal stability of acid-bile resistant Lactobacillus plantarum strains isolated from Siahmazgi traditional cheese

In this study, 22 Lactobacillus plantarum strains isolated from Siahmazgi traditional cheese were evaluated using different tests including resistance to low pH (1.50 and 2.50) and bile salt (0.50 and 1.00%), growth kinetic at low pH values and survival under simulated gastric and intestinal fluids. All the strains retained their viability at pH 2.50. However, the survival of all of the isolates was decreased at pH 1.50. Ten out of 22 strains which were able to tolerate low pH were selected for further investigations. All the selected isolates were able to grow at low pH. Strain F2 showed the highest specific growth rate. Five out of 10 isolates showed a significant decrease in bacterial count varied from 2.00 to 7.00 log CFU mL(-1 )during 3 hr exposure to 0.50% bile salt, while five isolates represented resistance to 0.50% bile during 3 hr. A significant reduction was observed in survival of all of the isolate at 1.00% bile salt concentration. Furthermore, viability of the selected isolates was lowered during 1 hr incubation under gastric conditions, while it remained unchanged within next 2 hr. Although, no significant changes were seen in bacterial count of the selected isolates during 1 hr of exposure to simulated intestinal condition, the survival of the isolates was relatively reduced after 3 hr. In conclusion, five out of 22 examined L. plantarum isolates showed appropriate resistance properties, therefore, could be good candidates for further examinations including functional and safety evaluation supporting their use as probiotics.