Research – Antilisterial and antistaphylococcal activity of a Lactococcus lactis strain isolated from Brazilian fresh Minas cheese

Lactococcus lactis QMF 11, isolated from Brazilian fresh cheese, produces bacteriocin like inhibitory substances (bac⁺). To evaluate L. lactis QMF11 possible application on biopreservation systems of dairy food, co‐inoculation studies were performed in pasteurized milk (8 °C, 10 days) targeting the inhibition of Listeria monocytogenes ATCC 7644 or Staphylococcus aureus ATCC 25923. Lactobacillus sakei ATCC 15521 was used as a negative control for bacteriocin production (bac⁻). L. monocytogenes and S. aureusreached 8 log CFU ml⁻¹ and 5.4 log CFU ml⁻¹ in monoculture, respectively, compared to <2.3 log CFU ml⁻¹ and 4.7 log CFU ml⁻¹ in co‐culture with L. lactis QMF 11. Instead, in the presence of the bac⁻, L. monocytogenes population reached 7.3 log CFU ml⁻¹ and S. aureuspopulations 5.5 log CFU ml⁻¹. These results indicate that L. lactis QMF11 may have potential for be use as biopreservative culture in dairy products, mainly because of its antilisterial activity.

Practical applications

There is a renewed interest in the use protective bacterial cultures or their metabolites to guarantee the microbiological safety and to extend the shelf life of dairy products, in a process called biopreservation. The research in this area has been leveraged by consumers demand for naturally preserved foods. Dairy products are natural niches for Lactococcus lactis strains, and these bacteria have been associated with food production and preservation since ancient times. As a dominant species in dairy ecosystems, L. lactisstrains are very interesting because they are not likely to require regulatory approval for practical application as bioprotective cultures.