Bacteriocins produced by wild Lactococcus lactis strains isolated from traditional, starter-free cheeses made of raw milk

Abstract

21Sixty bacterial strains were encountered by random amplification of polymorphic DNA 22 (RAPD) and repetitive extragenic palindromic (REP) typing in a series of 306 Lactococcus 23 lactis isolates collected during the manufacturing and ripening stages of five traditional, 24 starter-free cheeses made from raw milk. Among the 60 strains, 17 were shown to produce 25 bacteriocin-like compounds in both solid and liquid media. At a genotypic level, 16 of the 26 strains were identified by molecular methods as belonging to L. lactis subsp. lactis and one 27 to L. lactis subsp. cremoris. Among the L. lactis subsp. lactis strains, phenotypic and 28 genetic data determined that eleven produced either nisin A (nine strains) or nisin Z (two 29 strains), and that five produced lactococcin 972. Variable levels of the two bacteriocins 30 were produced by the different strains. In addition, nisin was shown to be produced in 31 inexpensive, dairy-and meat-based media, which will allow the practical application of its 32 producing strains in industrial processes. Specific PCR and nucleotide and deduced amino 33 acid sequence analysis identified as a lactococcin G-like bacteriocin the inhibitor produced 34 by the single L. lactis subsp. cremoris isolate. Beyond the use of bacteriocins as functional 35 ingredients for the biopreservation of foods, the newly identified bacteriocin-producing L. 36 lactis strains from traditional cheeses may also be useful for designing starter cultures with 37 protective properties and/or adjunct cultures for accelerating cheese ripening. 38 39

Comparative Phenotypic and Molecular Genetic Profiling of Wild Lactococcus lactis subsp. lactis Strains of the L. lactis subsp. lactis and L. lactis subsp. cremoris Genotypes, Isolated from Starter-Free Cheeses Made of Raw Milk

“…lactis LC44 of the cremoris genotype). These strains were previously identified by the sequencing of the 16S rRNA gene and comparison of the sequences against those in the GenBank and Ribosomal Database Project II databases (1 Molecular identification of strains. The identifications of the isolates were verified by molecular methods, which included partial amplified rRNA gene restriction analysis (ARDRA), sequencing, and sequence comparison.…”

Biodiversity in Oscypek, a Traditional Polish Cheese, Determined by Culture-Dependent and -Independent Approaches

“…The new cultures can also be used to complement or replace the starters currently used by the large-scale dairy industry (5). In addition, traditional cheese ecosystems may harbor LAB strains showing unique flavor-forming capabilities (4), enhanced bacteriophage resistance (31), or the production of new, broad-range antimicrobial agents (1).…”

Isolation and Characterization of Bacteriocin and Aggregation-Promoting Factor Production in Lactococcus lactis ssp. lactis BGBM50 Strain

“…Genes coding for the most common bacteriocins produced by L. lactis strains were sought by specifi c PCR primers (Table 2; 18,19). All amplifi cation reactions were conducted under standard conditions at an annealing temperature of 50 °C.…”