Microbial Biodiversity of Vietnamese Pickled Cucumber: Safety-Screening of Lactiplantibacillus plantarum DL8 as a Probiotic Candidate

Thuy Phuong Nguyen, Nguyen Thuy Linh

Abstract

Traditional fermented foods, such as Vietnamese pickled cucumbers, are essential sources of bacterial biodiversity, yet their functional characteristics in Vietnam remain underexplored. This study aimed to identify and evaluate promising probiotic candidates from this matrix. Presumptive lactic acid bacteria (LAB) isolates underwent a multi-stage screening process to assess simulated gastrointestinal tolerance, antimicrobial activity, and safety profiles using both phenotypic and genotypic assays. Identified via 16S rRNA sequencing as Lactiplantibacillus plantarum, strain DL8 exhibited remarkable tolerance to gastrointestinal stressors, successfully surviving at pH 3.0 and in 0.4% bile salts. It demonstrated broad-spectrum antimicrobial activity in neutralized cell-free supernatants (CFS) against key foodborne pathogens, including Escherichia coli, Staphylococcus aureus, and Salmonella enterica. Comprehensive safety testing showed that DL8 was non-hemolytic and sensitive to common clinical antibiotics. In addition, PCR-based genotypic screening confirmed the absence of virulence factors, vancomycin resistance genes, and genes encoding biogenic amine production. These in vitro findings indicate that L. plantarum DL8 represents a promising probiotic candidate and a potential protective starter culture for the regional food industry, requiring further validation through whole-genome sequencing and in vivo studies.

Keywords

antimicrobial activity; food safety; lactic acid bacteria; probiotics; traditional fermented foods

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