Isolation of antimicrobial lactic acid bacteria with potential use as a protective culture for ‘Queso Fresco’

Abstract

Lactic acid bacteria (LAB) isolated from various sources are used in the food industry for different purposes depending on their characteristics; being its antimicrobial capacity one of the most important. The objective of this work was to determine the antagonism of LAB’s isolated from milk and its derivatives against Salmonella, Staphylococcus and Listeria, contaminants of ‘queso fresco’ produced in the south of the state of Chiapas, Mexico, as a strategy for the development of protective crops for this artisan cheese. A total of 54 samples of dairy products (whey, milk and cheeses) from the Istmo-Costa region were analyzed. 52 strains of LAB were isolated, which were analyzed to investigate their antibacterial capacity by the methods of the drop on the surface and diffusion in agar. From the first method, 36 strains evaluated showed signs of being antagonistic to pathogens: nine against Staphylococcus aureus, seven against Salmonella sp. and five against Listeria monocytogenes. In the agar diffusion test, 31 strains evaluated showed antagonistic capacity: eight against S. aureus, 12 against Salmonella sp. and 11 against L. monocytogenes. These results encourage one to think that LAB’s isolated from dairy products may function as protective cultures from pathogens that contaminate ‘queso fresco’. Additional testing is required to validate this hypothesis.