Biological Characteristics of Limosilactobacillus reuteri K07 and Its Genetic Analysis
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Abstract:
Two strains of Limosilactobacillus reuteri (K07, K08) were isolated from traditional fermented cheese of Zhaosu County, Xinjiang Province. The growth, acid production, acid tolerance, bile salt tolerance, tolerance to simulated gastrointestinal tract, reuterin-producing capacity and antioxidant activity of the two strains were evaluated. In addition, the bacteriostatic performance of two strains was determined and genetic analysis of the K07 strain was performed. The results showed that both strains entered the late logarithmic growth phase after 12 hours of culture, and the endpoint pH of fermentation was 4.45. K07 exhibited stronger tolerance to acid, bile salt and the simulated gastrointestinal tract as well as higher antioxidant ability than K08. The survival rate of K07 was 73.27% after the treatment at pH 2.50 for 4 h. For the K07 strain, it took 5.50 hours for the OD600 nm to increase by 0.3 units under the stress of 0.15% bile salt. The survival rate of K07 in the simulated gastrointestinal test was 74.13%. The antioxidant activities of the cell-free extracts of the two strains were higher than those of the intact cells, with the scavenging rates of the cell free extracts of K07 for DPPH free radicals and hydroxyl free radicals were 42.39% and 15.69%, respectively. with the reducing power being17.96%. The amount of reuterin produced by K07 was 183.05 mmol/L, which was significantly higher than that of K08. Also, K07 exhibited better antimicrobial performance. The diameters of inhibition zones for Candida albicans and Streptococcus agalactiae were 22.20 mm and 18.26 mm, respectively. The full length of K07 genome was 1 950 440 bp, with 2067 predicted protein coding genes. The content of GC was 38.69%. The research results showed that Limosilactobacillus reuteri K07 had good probiotic properties, which provides a theoretical basis for subsequent industrial applications.
