Potential of yellow gentian aqueous-ethanolic extracts to prevent Listeria monocytogenes biofilm formation on selected food contact surfaces

Abstract

As a foodborne pathogen, Listeria monocytogenes could be commonly found in the food processing facilities, where forms biofilm on various food contact surfaces. Therefore, the control of L. monocytogenes biofilm formation is of key importance for improving food safety. The aim of this work was to examine the ability of yellow gentian root and leaf extracts to inhibit biofilm formation of L. monocytogenes strains at commonly used 37 °C and at ambient temperature associated with food processing plants (18 °C), on both polystyrene and stainless steel. Crystal violet staining assay revealed strong potential of the extracts to prevent biofilm formation on polystyrene at 37 °C (up to 90% inhibition), and on both surfaces at 18 °C (up to 78.1% and 62.9% on polystyrene and stainless steel, respectively). Antibiofilm effect could be ascribed to extracts’ ability to reduce the production of exopolysaccharides and to suppress swimming motility. Finally, qRT-PCR demonstrated no activity against quorum sensing, but up-regulation of the genes (flaA, sigB) involved in biofilm formation, most likely as a response to stressful conditions. Results obtained suggest yellow gentian extracts as potent antibiofilm agents, but further analyses are needed to determine the underlie mechanism and to validate the efficiency and safety in commercial environment.