Isolation of a broad-spectrum antibacterial lactic acid bacterium and evaluation of probiotic properties

Abstract:

[Objective] This study wanted to isolate and evaluate the probiotic properties of a broad-spectrum antibacterial lactic acid bacterium from Chinese traditional fermented soybean paste which was sampled from Jianhe country, Guizhou Province. [Methods] The strain DJ-04 was screened by antibacterial activity test, which was identified by physiological and biochemical characteristics and classification of 16S rRNA. The strain was examined for a series of assays including tolerance to artificial gastric intestinal juice, bile salt, and osmotic pressure. [Results] The strain DJ-04 was identified as Lactobacillus plantarum. It had an antibacterial activity against five pathogenic bacterium, including Escherichia coli, Salmonella sp., Staphylococcus aureus, Shigella sp., and Pseudomonas aeruginosa. DJ-04 had a strong tolerance to acid. The number of viable cells after 3 hours of incubation in pH 2.5 reached more than 107 CFU/mL. DJ-04 had a strong tolerance to artificial gastric intestinal juice since no significant changes were observed after 3 hours of incubation. The number of viable cells after 24 hours of incubation in 0.2 g/100 mL bile salt was above 108 CFU/mL. In addition, the number of viable cells after 24 hours of incubation in MRS containing 10 g/100 mL NaCl was more than 107 CFU/mL. [Conclusion] The isolated Lactobacillus plantarum DJ-04 had good tolerance to artificial gastric intestinal juice, bile salt, and osmotic pressure, suggesting that it could be a potential probiotics candidate for beneficial use.

Key words:Antibacterial activity, Artificial gastric intestinal juice, Bile salt, Osmotic pressure, Tolerance, Lactobacillus plantarum