Screening of probiotic Lactobacillus in simulated gastrointestinal environment

Abstract:

[Objective] To screen probiotic Lactobacillus as candidate strains for healthy yoghurt. [Methods] Lactobacilli isolated from healthy human feces and Milk Tofu were tested and screened by tolerance to simulated gastric juice. Probiotic potential was determined based on resistance to simulated gastrointestinal juice and bile salts, antibacterial activity, and cholesterol degradation ability. [Results] Results show that 41 bacterial strains with dissolved calcium were obtained from the Lactobacillus isolation medium. Five strains with high tolerance to low pH and simulated gastric juice were selected from the screened strains and identified by 16S rRNA gene sequencing. Three strains were Lactobacillus, named as Lactobacillus plantarum (LpMT-3), Lactobacillus plantarum (LpMT-5) and Lactobacillus salivarius (LsAF-7). These three Lactobacillus strains exhibited higher tolerance to simulated gastric juice than the commercially available LGG (Lactobacillus rhamnosus GG). After the Lactobacillus strains were transferred to intestinal juice for 26 h, survival rate of LpMT-5 was stable at approximately 45%, lower than LGG (49%). The three Lactobacillus strains displayed higher tolerance to bile salt than LGG when the concentration of bile salt was 0.10%. LpMT-3 and LsAF-7 were still alive when the concentration of bile salt was increased to 0.20%. All the three strains exhibited antibacterial activity, especially to Enterococcus faecalis, followed by Staphylococcus aureus, and the least inhibition effect to Escherichia coli and Salmonella. All three Lactobacillus strains also showed cholesterol-reducing ability. [Conclusion] Three strains of Lactobacillus could be taken as the strains to further develop new probiotic products and health yogurt.