Isolation of lactic acid bacteria from traditional yoghurts, identification by MALDI TOF MS biotyper system and determination of some starter culture characteristics

In this study, yogurt samples which were produced by traditional methods from some provinces around Bolu were collected and lactic acid bacteria (LAB) were isolated. Isolated strains were identified by MALDI-TOF MS Biotyper system. Of the 84 isolates isolated from the study, 2 were identified as Lactobacillus helveticus, 2 Lactobacillus plantarum, 3 Lactobacillus fermentum, 1 Enterococcus faecalis and 76 Lactobacillus delbrueckii. In order to determine the antibiotic resistance of the isolates, 16 different antibiotics were used and as a result, the susceptibility to erythromycin, teicoplanin, streptomycin, rifampicin, ampicillin, clindamycin, cefotaxime, chloramphenicol, tetracycline and vancomycin antibiotics was higher, whereas the majority of the isolates were nalidixic acid, ciprofloxacin, ofloxacin, gentamicin and showed resistance to trimethoprim sulfamethoxazole antibiotics. Acid production capabilities, diacetyl production, antimicrobial activities and protease activity of some isolates were investigated. For the analysis of antimicrobial activity, Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus and Bacillus cereus were used as indicator microorganisms. As a result, while the majority of the isolates did not show any inhibitory effect against Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus pathogens, the majority of isolates were found to have antimicrobial effect against Salmonella Typhimurium, E. coli O157:H7 pathogens. It was determined that the isolates mostly produced diacetyl production.