Resumo

Lactic acid bacteria can produce antimicrobial substances such as bacteriocins, able to inhibit the growth of foodborne pathogenic bacteria and applicable as food biopreservatives without changes in the sensorial quality of the product. The aim of this study was to isolate lactic acid bacteria with bacteriocinogenic activity of natural occurrence from raw goat milk produced in cities of Paraiba. Eighteen samples of raw goat milk were collected directly from animals from small farms located in the Cariri’s region of Paraíba and proceeded to the isolation of lactic acid bacteria and verification of antagonistic activity by plating on MRS surface at different time and temperature combinations: 25°C, 30°C and 35°C anaerobically for 48/72 hours and 30°C, 37°C for 48/72 hours, both in aerobiosis and in anaerobiosis and verification of the proteinaceous nature of the responsible substance for the inhibitory activity in the supernatant. Gram positive and catalase-negative isolated colonies were selected and the antagonistic activity against different indicator microorganisms such as Listeria monocytogenes Scott A, Listeria monocytogenes ATCC 7644, Listeria monocytogenes 711 (USP / Chiarini), Enterococcus faecium ATCC 19433, Staphylococcus aureus ATCC 13565, Salmonella spp 29 (UFPB / Farias) and Escherichia coli ATCC 29214 using the “spot on the lawn” method with modifications and expressed in arbitrary units per mL. The supernatants of the cultures were treated with the following enzymes: pepsin, α-chymotrypsin from bovine pancreas type II and protease type XIV from Streptomyces griseus, all of them at a concentration of 1.0 mg/mL. Only one from the twenty-four cultures that were isolated and tested, with small and milky colonies, presented bacteriocinogenic potential with inhibition against the Listeria monocytogenes 711 (USP/Chiarini) and Listeria monocytogenes ATCC 7644. The enzymatic treatments were able to inactivate the supernatant’s bacteriocins, confirming the proteinaceous nature of the bacteriocin. The metodology used for the isolation of lactic acid bacteria and detection of bacteriocin activity was shown to be feasible and appropriate for the proposed study and additional analyzes are needed to identify the spectrum of activity against other susceptible organisms as well as the identification of factors that may interfere with the antimicrobial activity.