Purpose: In this study, the bioprotective activity of a bacteriocinogenic LAB, isolated from Brazilian fresh Minas cheese and identified by 16S rRNA gene sequencing as Lactococcus lactis (strain 11), was evaluated.
Methods: Strain 11 was co-inoculated with food pathogens Listeria monocytogenes ATCC 7644 or Staphylococcus aureus ATCC 25923 in pasteurized milk, maintained at 8°C for up to 10 days. Lactobacillus sakei ATCC 15521 was used as negative control for bacteriocin production (LAB bac-).
Results: After incubation period, monocultures of L. monocytogenes reached 8 log CFU ml-1. In the presence of LAB bac-, L. monocytogenes population achieved 7.3 log CFU ml-1. However, when co-inoculated with strain 11, Listeria counts were maintained at the initial inoculum levels, not surpassing 2.3 log CFU ml-1. Regarding to S. aureus, in the end of the experiment, cultures counts were 5.4 log CFU ml-1 (monocultures), 5.5 log CFU ml-1 (co-inoculation with LAB bac-) and 4.7 log CFU ml-1 (co-inoculation with strain 11). Even though growth inhibition of S. aureus in the co-inoculation studies was not as evident as L. monocytogenes inhibition, S. aureus growth was significantly affected (P<0.005, according to Scott-Knott test) by the presence of strain 11.
Significance: These results indicate that Lactococcus lactis strain 11 has potential for use as a biopreservative culture in dairy products. Additional studies are being planned to confirm this assumption.
Funding Agencies: CNPq #482043/2013-0; FAPESP #2012/50507-1