Safety evaluation and identification of key genes from nisin operon in bacteriocinogenic strains isolated from goat milk

Abstract

Lactococcus lactis bacteriocin producers' strains were differentiated by repPCR. Applied chemicals, pH and temperature showed specific effect on the bacteriocin stability. Addition of CFS to the actively growing cultures of Listeria monocytogenes ScottA, Lactobacillus sakei ATCC 15521 or Enterococcus faecium ATCC 19434 resulted in the complete inhibition of bacterial growth. Different levels of adsorption of bacteriocin produced by studied strains to the test organisms were observed on bacteriocin and test organisms' specific manner, affected by temperature, pH and selected chemicals, important results for the prediction of potential optimal application of studied bacteriocins. Only between 200 AU/mL and 400 AU/mL were levels of adsorption of the bacteriocins to the cells surface on producers’ cells. The five tested strains resulted negative for the presence of different bacteriocins genes, except for nisin. Moreover, the targeted genes, parts of nisin operon, were detected partially in the DNA of DF2Mi and DF60Mi, suggesting that the bacteriocin(s) produced by these two strains differ from nisin. Studied strains were evaluated for presence of different virulence, antibiotics resistance and biogenic amines production associated genes, an important feature for their safety evaluation. Interaction between studied strains and commercial medicaments were evaluated in order to better model their potential application as probiotics.