Partial characterisation of peptides inhibiting Listeria growth in two Alpine cheeses
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Listeria monocytogenes, agent of food-borne listeriosis, is a major concern in dairy industry. The aim of this study was to assess the occurrence of peptides inhibiting Listeria spp. growth in two traditional Alpine pressed-curd cheeses: Emmental de Savoie and Asiago d’Allevo, and to get further insights regarding the characteristics of these peptides. Water-soluble extracts of these two cheeses were ultrafiltered onto 10,000-g.mol−1 cut-off filters to remove proteins and the corresponding filtrate was subsequently dialysed with 100–500-g.mol−1 cut-off membranes to remove salt and organic acids. A decrease from 53 ± 2% to 68 ± 1% of Listeria innocua LRGIA01 cells growth after 12-h incubation at 30 °C was observed in the presence of lyophilised extracts of the four cheese samples which were analysed. A less pronounced inhibition of L. monocytogenes 162 strain cells growth by cheese extracts was observed under the same conditions. After ultrafiltration onto 1,000 g.mol−1 cut-off membranes, all the extracts had almost the same anti-L. innocua activity, suggesting that most of antibacterial peptides had a molecular mass between 100–500 and 1,000 g.mol−1. The assay of the anti-L. innocua activity of fractions of Asiago cheese extracts separated by cation-exchange chromatography indicated that non-cationic peptides had a lower antibacterial activity. Taken together, these data suggest that most of antibacterial peptides present in Asiago cheese are low molecular mass and cationic peptides. A significant contribution of intact bacteriocins is thus unlikely; a contribution of either antimicrobial fragments of bacteriocins or caseins released by proteolytic enzymes during cheese ripening is more likely.
KeywordsCheese ripening Antimicrobial peptides Antilisterial activity Listeria innocua Listeria monocytogenes
The Emmental de Savoie cheese samples were provided by Actilait. The authors would like to thank Conseil Général de l’Ain and Communauté d’Agglomération de Bourg en Bresse for their financial support. The authors are finally very grateful to Agence Universitaire de la Francophonie for the PhD grant of Phuong NGUYEN THI.
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