Determining potential probiotic properties of human originated Lactobacillus plantarum strains

In this study, twenty Lactobacillus plantarum strains which were isolated from the fecal samples of humans were investigated in vitro for their characteristics as potential new probiotic strains. The L. plantarum strains were examined for resistance to gastric acidity in simulated gastric juice at pH 2.0, 2.5, 3.0, and 3.5. The growth of test cultures with different pH was monitored after 0, 10, 30, 60, 90, and 120 min of incubation using a spectrophotometer at 550 nm. At the same time, samples were serially diluted in sterile PBS, and counts of viable bacteria were determined by plate counts using MRS agar for each pH and time parameter. The strains were also examined for resistance to 0.4% phenol, production of H₂O₂, adhesion to Caco-2 cell line and antimicrobial activity. It was determined that the artificial gastric juice, even at pH 2.0, did not significantly change the viability of the cultures. Except L. plantarum AA1-2, all strains were detected at 8 ～ 9 log₁₀ CFU/g. It was found that all L. plantarum strains showed good resistance to 0.4% phenol, and only one strain (AC18-82) produced H₂O₂. Good adhesion of L. plantarum strains to Caco-2 cells was observed in this experiment. These selected strains also showed antimicrobial activity.