Determination of antimicrobial activity and identification of Lactococcus lactis isolates from milk

Lactic acid bacteria have been used as a starter culture to protect consumer health from pathogens by rapid acid formation and secreting natural antimicrobial agents for extending the product's shelf life. Use of Lactococcus lactis starters to produce fermented milk products increase the industrial importance of these species. These bacteria can form taste, aroma and contents of the food by fermentation and synthesized natural antimicrobial compounds (bacteriocin). The aim of this study was to determine antimicrobial activities, identification with phenotypic and PCR methods of Lactoccoccus lactis species from raw milk samples available for consumption in Amasya. Colonies inoculated into MRS Agar and colony morphology seen as a Lactococcus lactis, gram positive, catalase negative colonies then inoculeted into M17 agar and 154 strain isolated from 77 raw milk samples. %40 of these isolates has demonstrated antimicrobial activity on (ATCC 13076) Salmonella enteritidis, %33 on (ATCC 25923) Staphylococcus aureus, %29 on (DSM 4312) Bacillus cereus, %29 on (DSM 4312) Bacillus cereus, %29 on (ATCC 6633) Bacillus subtilis and %13 on (ATCC 35218) Escherichia coli using agar well diffusion technique. %59 of isolates showed inhibitory effect on at least one pathogen, %38 on two, %22 on three, %11 on four and %5 on all pathogens. 34 isolates have antimicrobial activity and %23 of these isolates were determined as Leuconostoc spp., %17,6 as Enterococcus faecalis, %17.6 as Lactococcus lactis ssp.cremoris, %14.7 as Lactococcus lactis ssp. lactis, %8.8 as Enterococcus faecium, %8.8 as Aerococcus viridans, %5.8 as Enterococcus durans and %2.9 as Enterococcus avium according to API 20 Strep test results. Determination were using PCR method %73 of 34 isolates typed as Lactococcus lactis ssp. cremoris, %82 of these typed as Lactococcus lactis ssp. lactis.