Isolation and Phylogenetic Analysis of Bacteriocin-producing Lactic Acid Bacteria from Retail Foods

Abstract

Lactic acid bacteria (LAB) are known producers of small, anti-microbial peptides termed bacteriocins. The first study looked at the presence of bacteriocin producing (Bac+) LAB on unprocessed retail foods. A total of 170 food samples from 108 different food products yielded 43 isolates with antimicrobial activity against Listeria monocytogenes. Isolated Bac+ LAB included Lactococcus lactis, Lactobacillus curvatus, Carnobacterium maltaromaticum, Enterococcus faecium, and Leuconostoc mesenteroides, including two Gram-negative bacteria, Serratia plymuthica, and Serratia ficaria. A wide variety of food products contain Bac+ bacteria, but the majority were isolated from fresh vegetables. These data propose that Bac+ LAB are widely dispersed as part of the natural flora of unprocessed foods.A second study examines the bacteriocin structural gene sequences of Enterococcus strains isolated from food as well as additional strains from animal sources. This second study utilizes a PCR primer array containing 16 primer pairs to detect bacteriocin structural genes in 22 Enterococcus spp isolates. Each isolate contained at least one of the screened structural gene with 15 of the 22 containing at least two. Enterocin A (entA), enterocins mr10A and mr10B (mr10AB), and bacteriocin T8 (bacA) were the most commonly found structural genes in order of decreasing prevalence. Our results display a high degree of bacteriocinogenic potential among enterococci which promise a part in biopreservation of food.