Maldi-tof mass spectrometry for the identification and detection of antimicrobial activity of lactic acid bacteria isolated from local cheeses

Abstract

In this study, 21 traditionally made cheeses were used. A total of 150 lactic acid bacteria (LAB) isolates were obtained from cheeses. 100 of them were identified at genus levels as Leunoconostoc (10), Lactobacillus (46) and Enterococcus (44) using biochemical tests. 71 strains were identified as Enterococcus durans (6), E. faecalis (18), E. faecium (24), E. italicus (2), Lb. brevis (1), Lb. paracasei (2), Lb. plantarum (1), Lactococcus lactis (3), Leuconostoc lactis (1), Leu. mesenteroides (11), and Streptococcus parauberis (2) at species levels using MALDI-TOF MS analysis. 10 of 100 isolates that showed antimicrobial activity were obtained from 21 samples of local cheeses. LAB strains were centrifuged to obtain supernatants in order to investigate two mechanisms. First, unprocessed supernatant was used to examine total antibacterial effect. Second, bacteriocins were obtained from LAB strains isolated using partial purification. The Kirby-Bauer Disk diffusion method was used to compare their antimicrobial activity against six pathogen. In conclusion, the bacteriocin produced from E. faecium shows higher antimicrobial activity than the others, and therefore, it can be used as a biological preservatives to extend shelf life.