Abstract
The antimicrobial activity of potentially probiotic strains is important for their possible application in the development of successful strategies for bio-preservation of different foods. The antimicrobial activity of the potentially probiotic strain Lactobacillus plantarum L4 against the pathogenic bacteria Salmonella abony; Staphylococcus aureus; Escherichia coli and the phytopathogenic fungi Aspergillus niger and Aspergillus flavus was determined using agar-diffusion assay with wells. Lb. plantarum L4 exhibited high antagonistic activity against all test microorganisms included in the study, which was due not only to the production and accumulation of lactic acid and other organic acids, but also to the production of other bioactive substances. The bioactive substances were then submitted to the action of different enzymes. This allowed to observe that they have protein nature, suggesting that they are likely bacteriocins or bacteriocin-like substances. The substances produced by Lb. plantarum L4 did not lose their antimicrobial activity during heat treatment at temperatures above 100 °С for 15 min and they exhibited high inhibitory activity against the test-microorganisms when pH ranged between 4 and 7. After further examination of the properties of the produced antimicrobial compounds, Lb. plantarum L4 can be used in the development of strategies for bio-preservation of different food products.
Highlights
Interest in food bio-preservation has considerably increased in the last decades due to the proven adverse effects of chemical preservatives on human health [1]
Bacteria and yeasts used in food production produce various compounds with antimicrobial activity, such as organic acids, diacetyl, H2O2, reuterin, bacteriocins and enzymes that exhibit bacteriostatic, bactericidal, fungistatic and fungicidal action against spoilage microorganisms and pathogens
In a series of experiments the supernatants obtained after the growth of the potentially probiotic strain Lb. plantarum L4 were tested for the presence of substances with antimicrobial activity and protein nature in the supernatants
Summary
Interest in food bio-preservation has considerably increased in the last decades due to the proven adverse effects of chemical preservatives on human health [1]. Bio-preservation is a method for preserving the quality of food and prolonging its shelf life by introducing substances of plant origin or microorganisms (most often lactobacilli and bifidobacteria), producing metabolites with high antimicrobial activity [3]. Bacteria and yeasts used in food production produce various compounds with antimicrobial activity, such as organic acids (lactic acid, acetic acid, propionic acid), diacetyl, H2O2, reuterin, bacteriocins and enzymes that exhibit bacteriostatic, bactericidal, fungistatic and fungicidal action against spoilage microorganisms and pathogens. They differ in the mode of antimicrobial action.
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