Assessing Activity and Characteristics of the Bacteriocins Produced by Lactobacilli from Local Yogurts of Behbahan City

Lactobacillus spp. are widely distributed in environment as well as dairy products. During the fermentation process, these microorganisms produce various compounds such as organic acids and bacteriocins with antimicrobial activities. The aims of this study were to isolate and identify lactobacilli from local yogurts of Behbahan, Iran, and assessment of antimicrobial activity of the bacteriocins produced by these lactobacilli.

In this study, the lactobacilli isolates were identified using 16S rRNA gene analysis. Antimicrobial effects of the bacteriocins were studied against five pathogenic bacteria using well diffusion and disk diffusion methods. Effects of proteolytic enzymes, heat and pH on these compounds were investigated as well.

Results of the well diffusion and disk diffusion methods showed that the most inhibitory effects on Shigella dysenteriae, Staphylococcus aureus, Pseudomonas aeruginosa, Micrococcus luteus and Listeria innocua belonged to Lactobacillus plantarum, Lactobacillus  acidophilus, Lactobacillus casei and Lactobacillus buchneri respectively. Micrococcus luteus was the most susceptible and Pseudomonas aeruginosa was the most resistant pathogens to effects of the bactericidal compounds. Antimicrobial compounds were inactivated by the proteolytic enzymes; however, the compounds preserved their resistance to heat and pH.

Bacteriocins produced by native lactobacilli are able to inhibit activity of various pathogenic microorganisms in foods and can be used as safe, harmless biological preservatives.