Screening and identification of bacteriocin-like inhibitory substances producing lactic acid bacteria from fermented products

A total of 544 isolates of lactic acid bacteria isolated from fermented products: 451 isolates from fermented products from Thailand and 93 isolated from French fermented products were screened for bacteriocin production. 10 isolates showed antimicrobial activities. Identification of the selected strains by random amplification of polymorphic DNA-polymerase change reaction using the primers E1, E2 and M13 showed three different RAPD patterns. One of the isolates from each product was chosen and good antimicrobial activity were displayed by 3 strains including MP6/2, PKS2-1 and OV1-1 producing in MRS broth bacteriocin-like substance (BLIS) inhibiting Candida albicans ATCC 90028, Carnobacterium maltraromaticum NCDO 2760, Lactobacillus sakei subsp. sakei JCM 1157, Listeria innocula CIP 80.11, Listeria ivanovii SLCC 2379, Pseudomonasc aeruginosa ATCC 27853, Staphylococcus aureus CIP 76.25 and Streptococcus mutans used as indicator strains. However, inhibitory activities of MP6/2 and PKS2-1 were related to the production of either organic acid, while OV2-1 was not affected by heating. The inhibitory activities of these three isolates were sensitive to proteolytic enzymes. 16S rDNA gene sequencing allowed to identify the MP6/2 as Pediococcus pentosaceus while PKS2-1 and OV1-1 were identified as Enterococcus faecium. It was concluded that the obtained isolates may be used as bio-preservative cultures to produce fermented foods.