Abstract

Objective: To isolate an antagonistic Lactobacillus strain from healthy infant feces and estimate its potential against a range of Gram-positive and Gram-negative bacteria. Methods: Isolation was based on biochemical tests and on 16S rDNA sequences. A PCR based screening of plantaricin bacteriocin encoding genes was conducted using specific primers. Antimicrobial activity was realized using spot on agar and agar well-diffusion tests. Spent culture supernatant was subjected to ultrafiltration. Effect of mitomycin C and UV light, heat treatment, storage, pH and enzymes were tested. Results: Biochemical tests and 16S rDNA sequences showed that LbM2a belonged to Lactobacillus plantarum. Screening of plantaricin genes showed the presence of plantaricin EF and K. Ultrafiltration tests lead to estimate the molecular weight between 3 and 10 kDa. LbM2a showed a broad inhibitory activity, which was stable at pH range of 2.0 to 6.0 and was proteinaceous (inactivation by proteolytic enzymes). Mitomycin C and UV light did not affect the activity. Conclusions: The paper illustrates that the ability of isolate and its bacteriocins in inhibiting a wide-range of bacteria are great interest for food safety and might have future applications as food preservative.

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