Control of Listeria monocytogenes biofilm on industrial surfaces by cell-free extracts of Lactobacillus plantarum
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In this study, the anti-microbial and anti-biofilm potential of the cell-free extract (CFE) of Lactobacillus plantarum was assessed against Listeria monocytogenes 32 isolated from the food sample. CFE of L. plantarum showed high anti-microbial activity (15.5 +/- 1.4 mm diameter zone) against L. monocytogenes 32. The anti-biofilm forming activity with the sub-minimum inhibitory concentration (MIC) value of CFE (15.625 mg/L) for 24 hr co-incubation period was obtained with the 90 +/- 7.9% inhibition. Co-incubation assay was also carried out on different surfaces such as stainless steel, polypropylene, and polyvinyl chloride. Viable cells in the formed biofilm were counted and the greatest reduction (5.22 log CFU/cm(2)) was achieved on polyvinyl chloride surface. Both biofilm formation and inhibition were also visualized by Scanning Electron Microscopy. It was observed that the biofilm of L. monocytogenes 32 was thread-like, binding one cell to another and the surface by the extracellular polymeric substance. Practical applications The dairy, meat, poultry, and seafood industries are the main food sectors where the biofilm formation of food-borne pathogens is observed. Listeria monocytogenes is one of the most noteworthy among them. High costs, procurement difficulties, or resistance problems limit the practical use of several approaches focused on the inhibition of L. monocytogenes biofilms. To prevent biofilm formation and/or to destroy cells embedded in biofilm via lactic acid bacterial strains and/or their metabolites has been remarkable in recent years. In the light of data obtained in this study, the cell-free extract of L. plantarum with its anti-microbial and anti-biofilm activity may be used to design as a bio-control strategy with its safe and environmentally friendly properties for prevention of biofilm formation of L. monocytogenes.