Study of lactic acid bacteria isolated from traditional ripened foods and partial characterization of their bacteriocins

Abstract

The antimicrobial activity of lactic acid bacteria (LAB) isolated from traditional ripened foods against various foodborne pathogens was evaluated, and the bacteriocins produced by the selected LAB of interest were characterized. For this, 33 bacteria were initially selected for their ability to produce proteinaceous compounds with antimicrobial activity. Subsequently, only three isolates were selected since they did not have virulence factors or were resistant to antibiotics. Due to the greater bacteriocin activity spectrum, Lactilactobacillus sakei 205 was selected, and its bacteriocin was characterized. The highest activity level (6400 AU/mL) was observed against Enterococcus faecalis ATCC 29212 during the growth of Lb. sakei 205 for 18–20 h. The bacteriocin, with an approximate molecular size of 24 kDa, remained stable at temperatures ranging from 25 °C to 60 °C, at pH values between 4.0 and 6.0 and was sensitive to all the detergents and inactivated with the proteolytic enzyme proteinase K, confirming its proteinaceous nature. Furthermore, it affected the viability of all the studied pathogens and repressed their growth for at least 12 h. In this preliminary study, the identified properties of Lb. sakei 205 strain and its produced bacteriocin indicate its potential application as a biopreservative in traditional ripened foods.

Se evaluó la actividad antimicrobiana de las bacterias del ácido láctico (LAB) aisladas de alimentos madurados tradicionales frente a diversos patógenos transmitidos por los alimentos, y se caracterizaron las bacteriocinas producidas por las LAB de interés seleccionadas. Para ello, inicialmente se seleccionaron 33 bacterias por su capacidad de producir compuestos proteicos con actividad antimicrobiana. Posteriormente, solo se seleccionaron tres aislados por no tener factores de virulencia ni ser resistentes a los antibióticos. Debido al mayor espectro de actividad de la bacteriocina, se seleccionó Lactilactobacillus sakei 205 y se caracterizó su bacteriocina. El nivel de actividad más alto (6400 AU/mL) se observó contra Enterococcus faecalis ATCC 29212 durante el crecimiento de Lb. sakei 205 durante 18–20 h. La bacteriocina, con un tamaño molecular aproximado de 24 kDa, se mantuvo estable a temperaturas entre 25 °C y 60 °C, a valores de pH entre 4,0 y 6,0 y fue sensible a todos los detergentes e inactivada con la enzima proteolítica proteinasa K, confirmando su naturaleza proteinica. Además, afectó la viabilidad de todos los patógenos estudiados y reprimió su crecimiento durante al menos 12 h. En este estudio preliminar, las propiedades identificadas de Lb. La cepa sakei 205 y su bacteriocina producida indican su aplicación potencial como bioconservante en alimentos madurados tradicionales.