SYNERGISTIC EFFECT OF LACTOCIN AL705 COMBINED WITH NISIN, POTASSIUM SORBATE, CALCIUM PROPIONATE AND SODIUM LACTATE AGAINST LISTERIA

VERDI, M.C.; CASTELLANO, P.; EISENBERG, P.; VIGNOLO, G.; BLANCO MASSANI, M.

Tucuman

Simposio; V International Symposium on Lactic Acid Bacteria (SIBAL). Benefitting from lactic Acid Bacteria. Progress in Health and Food.; 2016

CERELA-CONICET

Unlike most bacteria, Listeria can grow and multiply in some foods in the refrigerator, causing food borne outbreaks. To fight this microorganism, combinations of nisin (Nis) with sodium lactate (SL), calcium propionate (CP) and potassium sorbate (PS) were previously studied, showing synergistic inhibitory effects against Listeria innocua 7.Lactobacillus curvatus CRL705 produces the antilisterial bacteriocin(s) lactocin AL705. In order to reduce the quantity of antimicrobials used to inhibit Listeria, the present work aimed to study the effect of lactocin AL705 addition to the previously evaluated combinations. Inhibitory effects (bacteriostatic, bactericidal or bacteriolytic) of ternary mixtures were also studied.Lactocin AL705 was obtained by growing L. curvatus CRL1579 and subsequent ammonium sulfate precipitation. To assess the potential synergistic effect produced when adding AL705 to previously studied combinations, three-dimensional graphics were constructed representing the ternary mixtures AL705+Nis+X, with X: SL, CP or PS. The additive plane involving the CIM of each component was calculated. Three points were evaluated for each ternary combination by using the agar well diffusion method (i) an additive point on said plane; (ii) a point below, indicating synergistic interaction; (iii) a point above, indicating antagonism. Afterward, each ternary combination was incubated in Muller Hinton broth (pH 5.4, 24hs, 35C) with L. innocua 7 (106 CFU/ml), and colony counts were performed to assess their inhibitory effects. AL705 addition to Nis+X combinations showed synergistic effects allowing reduction of the antimicrobial amounts required to inhibit L. innocua 7: reduction of 61.6% (AL705), 97.5% (Nis), 90% (SL), 90% (CP) and 91.7% (PS). Besides, bacteriolytic activity was observed after incubating L. innocua 7 with each of the combinations. In conclusion, the results presented in this study demonstrated that AL705 combined with nisin, sodium lactate, calcium propionate or potassium sorbate had a synergistic effect while maintaining AL705 bacteriolytic effect against L. innocua 7. These results are promising for the design of strategies to fulfill consumer demands for safe and healthier foods.