NATURAL ANTIMICROBIALS FOR THE CONTROL OF FOOD-BORNE PATHOGENS

ISLA MARIA INÉS; CASTELLANO PATRICIA; MELIAN CONSTANZA; VIGNOLO GRACIELA; ZAMPINI CATIANA

san miguel de tucuman

Simposio; V Simposio Internacional de Bacterias Láctica.; 2016

Biopreservation or biocontrol refers to the use of natural or controlled microbiota, or its antibacterial products to extend the shelf life and enhance the safety of foods. Since lactic acid bacteria (LAB) occur naturally in many food systems and have a long history of safe use in fermented foods, thus classed as Generally Regarded As Safe (GRAS), they have a great potential for extended use in biopreservation. Antimicrobial substances from other natural sources, such as antimicrobial proteins or peptides from animal secretions, or bioactive molecules from plant have also been exploited in different ways for food biopreservation. Therefore, the objective of this study was to investigate the antibacterial activity of bacteriocins of Lactobacillus curvatus CRL705 and that of Zuccagnia punctata extract against pathogenic bacteria such as L. monocytogenes FBUNT and Escherichia coli ATCC25922. The synergistic and antagonistic effects between natural antimicrobials was also analyzed. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined by the broth microdilution method. The bactericidal activity of natural antimicrobials alone or in combination was confirmed by the time-kill curve.The semi-purified bacteriocins exhibited good bacteriostatic and bactericidal activity against L. monocytogenes, with an MIC and MBC of 53.33 and 426.67 UA/mL, respectively, while a lack of antibacterial activity against E. coli was observed. The plant extract demonstrated activity against both pathogens, with a MIC of 125 and 250 g/ml for L. monocytogenes and E. coli, respectively. The MBC of the plant extract against E. coli could not be determined because no complete inhibition was achieved even at highest assayed concentrations. Bacteriocins in combination with plant extract had a synergistic effect only against L. monocytogenes, enabling the use of lower antimicrobial concentrations. According to time-kill curve the log rates of both pathogens significantly decreased by treatments except for E. coli + bacteriocins. Only the combination of natural antimicrobials completely eradicated L. monocytogenes at the concentration of 2 × MIC after 6 h incubation, while E. coli decreased by 2.0 log cycles its population during the same time. The current study suggests the use of natural compounds, bacteriocins plus plant extract, as alternative biopreservatives for food. Further studies should be performed to elucidate the sensory impact in food model systems.