Métodos de obtenção e efeitos de metabólitos de Lactococcus lactis sobre bactérias residentes do trato gastrointestinal

Abstract

This study aimed to obtain secondary metabolites of Lactococcus lactis subsp. lactis and evaluate its efficacy in inhibiting bacterial growth in vitro. 10 μl of L. lactis bacterial suspension was plated at 103 cells concentration, which were seeded onto M17 agar. Plates were incubated at 30 ° C for 20 hours. The cell number was read at each hour interval and the time corresponding to the stationary phase was identified. L. lactis was cultured in M17 medium at 30øC for 16 hours and the secondary metabolites were extracted. 90 μl of the metabolic extract was inoculated together with 10 μL of Muller Hinton broth with test microorganisms: Escherichia coli, Enterococcus faecalis, Enterobacter sakazakii, Lactococcus lactis and Salmonella enteritidis, according to the standards of The Clinical and Laboratory Standards Institute. The secondary metabolites were extracted by centrifugation at 6000 rpm for 10 minutes. The metabolites showed inhibitory action at different intensities on the growth of the test microorganisms. Both microorganisms Escherichia coli and Enterobacter sakazakii presented inhibition index 37% and Salmonella enteritidis 93%. Lactococcus lactis and Enterococcus faecalis showed growth promotion index of 30% and 20%. It is concluded that the extract obtained stimulated the growth of the bacteria Enterococcus faecalis and Lactococcus lactis, suggesting the presence of substances that favor the survival of these microorganisms, and inhibited the growth of Escherichia coli, Enterobacter sakazakii and Salmonella enteritidis.