Whole genome sequence analysis and in vitro probiotic characteristics of a Lactobacillus strain Lactobacillus paracasei ZFM54.

Abstract

The aim was to identify a Lactobacillus strain with potential probiotic characteristics by whole-genome sequence analysis and in vitro experimental studies. The whole-genome sequencing was carried out using PacBio RSII sequencing method and Illumina's paired-end sequencing technology. Gene prediction and annotation were achieved using GlimmerVersion 3.02 and NCBI prokaryotic Genome Annotation Pipeline. Identification was done by biochemical tests and 16S rRNA sequence analysis. mega 6 software was used to build phylogenetic tree. Antagonism against pathogen was determined by agar well diffusion method. Resistance and stability to bile, simulated gastric acid, different salt concentration and thermostability were investigated. Hydrophobicity assay, aggregation assay and anti-oxidation assay were performed to check further probiotic traits. Finally antibiotic susceptibility and acute oral toxicity of the strain in mice were investigated to check its safety status. The strain showed >99% similarity to Lactobacillus paracasei which was further confirmed by biochemical tests. It significantly inhibited pathogens in agar well diffusion assay. It showed tolerance to simulated gastric acid (pH 3), 0·3% bile salt and 10% NaCl. Significant hydrophobic, aggregation and anti-oxidizing activities were observed. No resistance to antibiotics tested was observed and no adverse effects during acute oral toxicity in mice were detected. Lactobacillus paracasei ZFM 54, a new and safe Lactobacillus strain was identified with numerous probiotic-associated genes and characteristics confirmed by experimental studies. A new probiotic strain has been identified which is highly stable, safe and suitable to be used in health and food industries.