Screening for Lactobacillus plantarum with potential inhibitory activity against enteric pathogens

Abstract

Three hundred and forty-seven strains of Lactobacillus plantarum previously isolated from Chinese and Mongolian traditionally fermented foods were preliminary evaluated for their probiotic properties, including their resistance to simulated gastrointestinal fluids and bile salts, and their antibacterial activity. Fifteen strains showed broad-spectrum inhibitory activity against five indicator enteric pathogens. Seven out of these 15 strains showed high tolerance to both simulated gastrointestinal fluids and bile salts. Further preliminary experiments (by pH adjustment, treatment with catalase, pepsin, and trypsin or heat) were performed to characterize the nature of antibacterial materials in the cell-free supernatants. The antibacterial property was suppressed by the adjustment to pH 6.0 except for strain IMAU80087, suggesting that such activity was pH-dependent for most of the characterized strains. The antibacterial activity of IMAU70104 and IMAU80184 was largely hydrogen peroxide-based, whereas the antibacterial property of IMAU70010 and IMAU80171 was possibly peptide/protein in nature. The antibacterial materials of IMAU80076 and IMAU70088 were partially sensitive to pepsin treatment. Finally, the antibacterial material in the cell-free supernatant of IMAU80087 was strongly resistant to pH change and most treatments used in this study, which makes it particularly desirable for application in neutral food. The current study has identified novel L. plantarum strains and valuable microbial resources, which are of good potential to be applied in controlling the growth of pathogenic food bacteria.