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    Assimilation of cholesterol and probiotic characterisation of yeast strains isolated from raw milk and fermented foods
    (WILEY-BLACKWELL, 2016) Aloglu, Hatice Sanlidere; Ozer, Ezgi Demir; Oner, Zubeyde
    In this study, cholesterol assimilation ratios and some probiotic characteristics of yeasts were investigated. For this purpose, yeasts were isolated from milk and foods that were naturally fermented and not containing starter culture. In vitro cholesterol assimilation properties were determined in media. The Cholesterol assimilation by yeast strains ranged between 1.36 and 73.33%. Twenty-one yeast strains showing high assimilation percentage were selected, and their acid tolerance, bile tolerance, bile salt deconjugation activity and survival in simulated gastrointestinal conditions were investigated. Among the strains assessed, 12 of them showed probiotic characteristics.
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    Investigation of a Probiotic Yeast as a Cholesterol Lowering Agent on Rats Fed on a High Cholesterol Enriched Diet
    (KAFKAS UNIV, VETERINER FAKULTESI DERGISI, 2015) Aloglu, Hatice Sanlidere; Ozer, Ezgi Demir; Oner, Zubeyde; Savas, Hasan Basri; Uz, Efkan
    Probiotic yeast, Cryptococcus humicola M5-2 strain, which has high cholesterol assimilation feature and isolated from traditionally produced cheese, was investigated in vivo. This study was conducted to determine cholesterol assimilation ability of C. humicola M5-2 in vivo and specify the effect of the strain on serum total cholesterol, HDL/LDL cholesterol and triglycerides levels in rats fed on cholesterol-enriched diet. C. humicola had the ability to assimilate cholesterol at the rate of 73.33% in media. The strain was used with two different concentrations in animal feed (high and low doses containing 2% and 0.1% lyophilized strains, respectively). When the treatment groups were compared, low dose feeding group had the positive results in terms of testing values. According to the results of serum analysis, triglyceride and total cholesterol level were decreased by 25% and 1.34% respectively. Especially, decreasing the percentage rate of triglyceride has not obtained in other in vivo studies. It is thought that health promoting effect will be possible when the obtained isolate is consumed with fermented foods.
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    Physico-chemical and microbiological changes occurring in Kuru Kaymak (a traditional dairy product in Turkey) during storage
    (Indian Dairy Assoc, 2022) Ozer, Ezgi Demir; Yildirim, Metin
    The aim of this study was to determine the changes in some physico-chemical and microbiological properties of Kuru Kaymak (KK) (Dry Clotted Cream) during 30 days of storage at 4 degrees C. Kuru Kaymak samples were produced in a local family business on a small scale using the traditional method. The dry matter, fat, protein, lactose and ash content, and the water activity value of KK samples on the 30th day were 97.4%, 64.2%, 23.5%, 4.40%, 1.69% and 0.59, respectively. Unlike other high-fat dairy products, Kuru Kaymak samples were found to contain a fairly high amount of protein (23.5%). The free fatty acid value showed an enormous increase of 266.7% from 0 to 30 days. Yeast and mould counts of KK samples were below the countable level (<2 log cfu/g) throughout storage. The presence of coliform bacteria in KK samples showed that there was contamination due to noncompliance with hygienic rules in production. Considering the properties examined, it was concluded that KK could be stored for more than 30 days at 4 degrees C without any noteworthy deterioration.
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    The modification of nisin with homocysteine thiolactone and its effect on antimicrobial activity
    (Springer, 2024) Ozer, Ezgi Demir; Yildirim, Metin
    The aim of the present study is to make an important contribution to the literature by focusing on the preparation of the N-homocysteine conjugate of nisin and evaluating the effect of the N-homocysteinylation reaction on its antimicriobial activity. The modification process was monitored using both acetic acid urea polyacrylamide gel electrophoresis (AAU-PAGE) and tricine sodium dodecyl sulphate polyacrylamide gel electrophoresis (tricine SDS-PAGE). The antibacterial effectiveness of modified nisin was assessed against Staphylococcus aureus ATCC 6538, Enterococcus faecium ATCC 9097, Bacillus subtilis ATCC 6633, Lactococcus lactis ssp. cremoris Au, Listeria monocytogenes NCTC 5348, and Escherichia coli RSKK. Optimal conditions for achieving the highest N-homocysteinylation degree (6.30%) were determined as 6 mg/mL nisin, 150 mM homocysteine thiolactone, 150 rpm shaking rate, pH of 3.0, and a reaction time of 6 h. The modified nisin obtained did not have a significant inhibitory effect on the strains tested except E. faecium. E. faecium was inhibited by the modified nisin and its antibacterial activity was determined as approximately 10% of the antibacterial activity of unmodified nisin. On the other hand, hydrolysis of nisin by trypsin and thermolysin resulted in significant specific side chain modifications induced by the homocysteine-thiolactone reaction, especially at Lys12 and Lys22. The results provide valuable insights into the potential of N-homocysteinylation to improve the antibacterial properties of nisin and also suggest that the effects of specific modifications identified during the modification process should be investigated.