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    Comparison of the probiotic characteristics of Lactic Acid Bacteria (LAB) isolated from sourdough and infant feces
    (Elsevier, 2022) Kaya, Yasemin; Erten, Tayyibe; Vurmaz, Melike; Ispirli, Humeyra; Simsek, Omer; Dertli, Enes
    Probiotics are beneficial microorganisms with certain characteristics such as survival under gastrointestinal conditions, adhesion to intestinal surface and different functions which result in several health benefits to host. With this regards, this study aimed to isolate Lactic Acid Bacteria (LAB) from sourdough and human feces as two different environments and to test their potential probiotic functions. In total nine distinct isolates were assessed with several probiotic functions such as in vitro adhesion to human colon cells, antimicrobial activities and survival under harsh gastrointestinal conditions. In general, distinct strains showed strong antimicrobial activity against the pathogenic and fungal strains tested in this study. Importantly, the adhesion levels to HT29 cells were determined between 0.29 % and 9.54% and Lactobacillus paracasei F7B showed the highest adhesion. All isolates tolerated the bile salt after 24 h and the infant feces isolates showed good survival characteristics at pH 4.
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    Diversity of Clostridium spp. causing late blowing in Kas , ar cheese and their behaviour against various antimicrobials
    (Elsevier Sci Ltd, 2023) Kaya, Halil Ibrahim; Simsek, Omer; Akgunoglu, Ozlem
    One of the problems encountered during storage of Kas , ar cheese is blowing. The diversity of Clostridium spp. having a role in blowing was screened and the sensitivity of Clostridium spp. strains against nisin, NaCl, CuSO4, and EDTA was determined and compared. According to 16S rDNA sequence similarity, 12 Clostridium spp. isolates were Clostridium sporogenes while 3 were Clostridium jeddahense. Gas formation by Clostridium spp. spores can be significantly inhibited by reducing the pH below 5.5 and adding 400 IU mL-1 nisin when the number of spores are below 300 spore mL-1. It was determined that the late -blowing problem in Kas , ar cheese is caused by C. sporogenes and C. jeddahense strains, but the success of preventive agents is closely related to the amount of spores.(c) 2022 Elsevier Ltd. All rights reserved.
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    Expanding Layers of Bacteriocin Applications: From Food Preservation to Human Health Interventions
    (Mdpi, 2025) Demirgul, Furkan; Kaya, Halil Ibrahim; Ucar, Redife Aslihan; Mitaf, Naciye Afranur; Simsek, Omer
    Bacteriocins, ribosomally synthesized by bacteria, have long been recognized for their role in ensuring food safety and security due to their antibacterial effects against foodborne pathogens and spoilage bacteria. However, recent advancements have unveiled their expanding potential beyond food applications, with increasing evidence of their efficacy against clinically significant pathogenic bacteria, biofilm formation, viral infections, and even cancer. These emerging discoveries have continuously added new layers to the application of bacteriocins, extending their relevance from food preservation to broader human health interventions. To further harness this expanding potential, various innovative strategies have been developed to overcome traditional limitations associated with bacteriocin use. Instead of directly employing bacteriocins or bacteriocin-producing bacterial cultures, novel approaches, such as incorporating them into films and packaging materials or coupling them with nanoparticles, have demonstrated enhanced effectiveness. In this review, we examine the evolving landscape of bacteriocin applications and shed light on the expanding functional spectrum of bacteriocins for both food safety and human health, although some important challenges and limitations remain. By analyzing the recent literature and innovative technological advancements, we highlight how bacteriocins are continuously evolving, opening new frontiers for their use and reinforcing their significance beyond their conventional roles.
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    Identification of additional probiotic attributes in yeasts isolated from tarhana fermentation
    (Springer, 2025) Erdem, Belgin; Kaya, Halil Ibrahim; Tulumoglu, Sener; Coteli, Ebru; Simsek, Omer
    Fermented foods constitute a valuable source of probiotics for both bacteria and yeasts. To date, however, there has been a limited amount of research conducted on Saccharomyces cerevisiae, Kazakhstania servazzi, Kluyveromyces marxianus and Torulaspora delbrueckii isolated from tarhana. The objective of the research is to identify additional probiotic characteristics other than the leavening activity exhibited by yeasts that were previously isolated from tarhana fermentation. In this study, yeasts were subjected to subsequent acid and bile salt tolerance, bile salt hydrolysis, antagonistic activity, aggregation activity (auto-aggregation and co-aggregation), cholesterol assimilation, folate production, biofilm production, and hemolysis activity. S. cerevisiae PCF122, S. cerevisiae PCF107, and S. cerevisiae PCF134 strains grew at pH 2 and 2,5 but remained at pH 3. Except for S. cerevisiae PCF115 and T. delbrueckii PCF150, all yeasts were found to be 0,5% and 1,0% oxalate tolerant. All yeasts hydrolyze oxalate (bile salt), but only S. cerevisiae PCF115 and T. delbrueckii PCF150 produced EPS. Yeasts also exhibited significant amounts of autoaggregation (46-87%). After 24 and 48 h incubation, all strains assimilated cholesterol at rates ranging from 10,4% to 87,5% and 10,6-91%, respectively. The highest folate production was determined at S. cerevisiae PCF108 (56 mu g/mL) and the lowest was at S. cerevisiae PCF110 and K. marxianus PFC120 (18 mu g/mL). In conclusion, yeasts that existed in tarhana fermentation showed cholesterol assimilation, folate production, and aggregation activity which are additional probiotic attributes that would have consumer health promotion, beside these yeast leaven the tarhana dough.
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    Structural and technological characterization of ropy exopolysaccharides produced by Lactobacillus plantarum strains isolated from Tarhana
    (Korean Society Food Science & Technology-Kosfost, 2020) Zehir Senturk, Duygu; Dertli, Enes; Erten, Huseyin; Simsek, Omer
    Exopolysaccharide producing starter cultures enable manufacturing clean labeled foods with improved textural and nutritional properties. The structural and technological analyses were performed on the ropy exopolysaccharides of six Lactobacillus plantarum. The incubation temperature, time and pH affected the exopolysaccharide production and high exopolysaccharide was produced in the presence of sucrose and maltose. The viscosity of exopolysaccharide was high at acidic conditions except PFC311E that showed viscous at neutral pH. Lactobacillus plantarum strains produced between 120 and 400 mg/L exopolysaccharide in which the highest was observed at L. plantarum PFC311. Exoploysaccharides were degraded over 300 degrees C except PFC311E that degraded at 295.7 degrees C. The NMR analyses revealed that the exopolysaccharides were synthesized by alpha 1-6, alpha 1-3 and alpha 1-4 bonds with glucose, galactose and fructose moieties. In conclusion, L. plantarum PFC311 produced ropy exopolysaccharide with different structural, rheological and thermal properties and reveals potential to be used in food industry.