Identification of presumptive enterococcus strain with antimicrobial activity isolated from white cheese and determination of its functional properties

The aim of this master's thesis is to identify the presumptive bacteriocin-producing enterococcus strain isolated from Turkish White cheese (Polymerase Chain Reaction (PCR) with genus-specific and species-specific primers, 16S rRNA gene region sequence analysis), to determine the bacteriocin produced by the strain using known enterocin primers and to identify some technological and probiotic properties. As a result of activity spectrum tests, the presumptive enterococcal isolate showed the highest inhibitory activity against Listeria monocytogenes, followed by Staphylococcus aureus and vancomycin-resistant enterococci. As a result of proteolytic enzyme application, it was determined that the antimicrobial substance produced by the enterococcus isolate was bacteriocin. The enterococcal isolate was identified as Enterococcus faecium BT29.11 by 16S rDNA sequence analysis and genus and species-specific PCR. As a result of PCR studies carried out with primers belonging to known enterocin structural genes, it was determined that E. faecium BT29.11 has entA, entB and entX structural genes. The ΔpH value of E. faecium BT29.11 strain at the 6th and 24th hour of incubation in RSM medium was calculated as 0.41±0.004 and 0.82±0.001; and in MRS medium, 1.470±9.19 and 2.044±18.38, respectively. E. faecium BT29.11 grew at a rate of 2.19% and 21.36% in media containing phenol and lysozyme, respectively. It was determined that E. faecium BT29.11, which was inoculated into gastric juice with pH adjusted to 3, remained alive at a rate of 98.44% at the end of three hours of incubation. In addition, BT29.11 strain showed growth rates of 24.78%, 13.90% and 1.70% on media containing 0.3%, 0.5 and 1% bile salt, respectively. As a result of survival experiments of E. faecium BT29.11 at low pH, the number of cells decreased to an undetectable level at pH 1.0 from the first hour of incubation. However, it was determined that the BT29.11 strain maintained its viability for 4 hours at pH 3.0 and pH 5.0. The autoaggregation value of E. faecium BT29.11 and L. monocytogenes ATCC7644 was found to be 56.89±2.47% and 25.35±1.89%, respectively. Additionally, the coaggregation rate of E. faecium BT29.11 with L. monocytogenes ATCC7644 was determined as 43.95±1.78%. The hydrophobicity value of E. faecium BT29.11 was determined as 44.35% ±0.71. The findings obtained from the thesis study showed that enterocin producer E. faecium BT29.11, originating from Turkish white cheese, may have the potential to be used as an adjunct probiotic culture.