Isolation and Molecular Identification of Bacteriocin-Associated Lactobacillus Strains from Indigenous Fermented Food

Abstract

Bacteriocin-producing Lactobacillus species have been observed for their ability to inhibit foodborne pathogens and enhance food safety and serving a natural biopreservatives and probiotics. This study aimed to isolate and characterize bacteriocin-producing Lactobacillus strains from selected indigenous fermented foods for potential application in the food industry in Nigerian. The fermented food samples were serially diluted and were cultured on de Man, Rogosa and Sharpe (MRS) agar and used to isolate lactic acid bacteria (LAB). The isolates were characterized by using morphological, biochemical methods and molecular identification based on 16S rRNA gene amplification and sequencing. The LAB isolates that were predominant were subsequently screened for the presence of the gassericin bacteriocin gene using polymerase chain reaction (PCR) to screen for bacteriocin-producing potential. Phenotypic and molecular characterization identified the predominant isolates as Lacticaseibacillus paracasei, Lactiplantibacillus plantarum, Limosilactobacillus fermentum, and Limosilactobacillus reuteri, each were able to produce a distinct 16S rRNA gene amplicon of approximately 1,500 bp. The gassericin-associated gene, with an expected amplicon size of approximately 800 bp, was detected in all predominant isolates. Out of the 30 LAB isolates that were screened, 19 (63.33%) were positive for the targeted bacteriocin-associated genetic marker, with frequency of occurrence ranging from 50% in fermented melon seeds (Ogiri) to 70% in fermented milk. These findings in this study have shown that indigenous Nigerian fermented foods can constitute valuable reservoirs of lactobacilli that possess genes for bacteriocins, with potential applications as starter cultures, natural biopreservatives, and probiotic candidates that can be used to improve food safety and extend the shelf life of fermented foods and other food products.