Ekşi Hamurlardan İzole Edilen Lactobacıllus Brevis ve Lactobacıllus Plantarum’un Antimikrobiyel Etkilerinin İncelenmesi

Abstract

Nowadays, the interest in safe products is increasing due to the increasing awareness of consumers and the desire of consumers to consume healthier products. Industrially, the long shelf life of foods provides benefits to consumers, producers and market chains. In order to produce long-lasting and safe products, the use of probiotic microorganisms as protective cultures comes to the fore. In this thesis, it was aimed to investigate the probiotic properties of non-commercial L. brevis and L. plantarum bacteria isolated within the scope of the doctoral thesis (Tezer, 2019). Within the scope of the research, 3 Lactobacillus plantarum (Iz1, Wz3, Hp2) and 1 Lactobacillus brevis (Gc3) isolates were used. Some probiotic properties of these isolates were investigated and catalase tests were performed. In the studies, antimicrobial properties of lactic acid bacteria against various food pathogens (Salmonella enterica subsp. enterica serovar Enteritidis, Listeria monocytogenes, Enterohemorrhagic Escherichia coli, methicillin resistant Staphylococcus aureus) were investigated. All four of the lactic acid bacteria used in this thesis study were found to have antimicrobial susceptibility to food pathogens. Iz1 strain showed the highest antimicrobial activity to methicillin resistant Staphylococcus aureus pathogen, Wz3 and Hp2 strains showed the highest antimicrobial activity to Listeria monocytogenes pathogen. The food pathogen to which Gc3 strain showed the highest antimicrobial activity was Salmonella Enteritidis. Enterohemorrhagic Escherichia coli (EHEC) was the pathogen with the lowest effect of all lactic acid bacteria. The food pathogen to which the metabolites produced by lactic acid bacteria showed the highest antimicrobial activity was Listeria monocytogenes. The lowest activity shown by the cell-free supernatants of Iz1 and Wz3 strains was against EHEC. The lowest antimicrobial activity of the Gc3 supernatant was against methicillin resistant Staphylococcus aureus, and the Hp2 supernatant against Salmonella Enteritidis. Supernatants were also tested against pathogens by the broth microdilution method. The Minimal Inhibitory Concentration (MIC) of lactic acid bacteria was evaluated by the broth microdilution test. Supernatants from all selected lactic acid bacteria strains inhibited pathogen growth by 50% or more when used at ≥30-35%. When the cell-free supernatants were used at 50% concentration, the highest inhibition of Iz1 was against MRSA, the highest inhibition of Gc3 was against L. monocytogenes, the highest inhibition of Wz3 was against. S. Enteritidis, the highest inhibition of Hp2 was against MRSA. In order to further investigate one of the properties of lactic acid bacteria, whether they contain the enzyme catalase was determined by the catalase test. It was concluded that all 4 lactic acid bacteria were catalase-negative. As a result of the thesis study, 4 non-commercial lactic acid bacteria strains also gave positive results in terms of probiotic properties and no contrary findings were found. In this study, it is aimed to continue the studies to prove the probiotic properties of lactic acid bacteria and if proven, commercial use of these non-commercial strains in the food industry and bringing them to the culture collection will make a significant contribution.