Browsing by Author "Ozaktas, Tugba"

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Comparison of Antioxidant Activity, Metal Chelating Power and Antibacterial Activity in Different Tissues of Alcea Calvertii (Boiss.) Boiss
(2023) Biçek, Ayşe Gözde; Kartal, Denız Irtem; Özgökçe, Fevzi; Ozaktas, Tugba
The traditionally used plant Alcea calvertii (Boiss.) Boiss. (Malvaceae) was extracted by two more methods in addition to those used by the locals, in this study. It was found that ethanol extraction significantly improved the release of total phenolic content of all plant parts compared to extraction by infusion and traditional use. In addition, ethanol appears to be a good solvent for the extracting flavonoids and phenolic contents from A. calvertii. However, metal chelating power was found to be higher in the infusion extracts than in the ethanolic extracts. The antibacterial activities of all extracts from the plant parts were also tested. As a result, it has been confirmed in this study that A. calvertii is rich in phenolic compounds and flavonoids and has high antioxidant activity with strong metal chelating power, however, the right plant parts must come together with the right extraction method for this effect to occur.
Comparison of the Effects of Adding Microbial Transglutaminase To Milk and Ice Cream Mixture on the Properties of Ice Cream
(Wiley, 2020) Merve, A. L.; Ersoz, Fatma; Ozaktas, Tugba; Turkanoglu-Ozcelik, Aysun; Kucukcetin, Ahmet
In this study, the effect of recombinant microbial transglutaminase enzyme on the physicochemical properties of ice cream produced by two different methods was investigated. For this purpose, different enzyme units (2, 4 and 6 U/g milk protein) were applied to both ice cream mixture and milk. While with the first method, a 10% increase in the overrun value of ice cream samples was observed, a 7% increase was obtained by the second method. All ice cream samples exhibited pseudoplastic behaviour. This study indicated that transglutaminase concentration is an important factor in terms of improving the physicochemical properties of ice cream.
High Level Multiple Antibiotic Resistance Among Fish Surface Associated Bacterial Populations in Non-Aquaculture Freshwater Environment
(Pergamon-elsevier Science Ltd, 2012) Ozaktas, Tugba; Taskin, Bilgin; Gozen, Ayse G.
Freshwater fish, Alburnus alburnus (bleak), were captured from Lake Mogan, situated in Ankara, during spring. The surface mucus of the fish was collected and associated bacteria were cultured and isolated. By sequencing PCR-amplified 16S RNA encoding genes, the isolates were identified as members of 12 different genera: Acinetobacter, Aeromonas, Bacillus, Brevundimonas, Gordonia, Kocuria, Microbacterium, Mycobacterium, Pseudomonas, Rhodococcus, and Staphylococcus, in addition to one strain that was unidentified. The mucus-dwelling bacterial isolates were tested for resistance against ampicillin, kanamycin, streptomycin and chloramphenicol. About 95% of the isolates were found to be resistant to ampicillin, 93% to chloramphenicol, and 88% to kanamycin and streptomycin. A Microbacterium oxydans and the unidentified environmental isolate were resistant to all four antibiotics tested at very high levels (>1600 mu g/ml ampicillin and streptomycin; >1120 mu g/ml kanamycin; >960 mu g/ml chloramphenicol). Only a Kocuria sp. was sensitive to all four antibiotics at the lowest concentrations tested (3.10 mu g/ml ampicillin and streptomycin; 2.15 mu g/ml kanamycin; 1.85 mu g/ml chloramphenicol). The rest of the isolates showed different resistance levels. Plasmid isolations were carried out to determine if the multiple antibiotic resistance could be attributed to the presence of plasmids. However, no plasmid was detected in any of the isolates. The resistance appeared to be mediated by chromosome-associated functions. This study indicated that multiple antibiotic resistance at moderate to high levels is common among the current phenotypes of the fish mucus-dwelling bacterial populations in this temperate, shallow lake which has not been subjected to any aquaculturing so far but under anthropogenic effect being in a recreational area. (C) 2012 Elsevier Ltd. All rights reserved.
Isolation and Characterization of Chlorpyrifos-Degrading Bacteria From Turkish Tobacco Field Soil
(Taylor & Francis inc, 2025) Yavas, Merve; Ozaktas, Tugba
Pesticide contamination has become a major environmental concern with organophosphates such as chlorpyrifos emerging as major pollutants posing significant risks to both ecosystems and human health. Chlorpyrifos is widely used in agriculture to control pests, however due to its persistence, its accumulation in soils can lead to long-term environmental damage. The objective of this study was to isolate and characterize chlorpyrifos-degrading bacteria from a tobacco field exposed to intensive pesticide use in T & uuml;rkiye. To achieve this, a selective enrichment strategy was employed to promote the growth of chlorpyrifos-degrading microorganisms. Two distinct experimental setups were established to target both normally growing and slower-growing bacteria: the first involved a 4-week incubation with weekly subculturing as described in the literature, while the second applied an 8-week incubation with biweekly subculturing. At the end of the enrichment period, bacterial loads were compared between the two groups. Four of the nine bacterial isolates were obtained from the newly tested long-term setup. Among all isolates, members of the genus Pseudomonas exhibited the best adaptation to the prolonged enrichment conditions. Additionally, isolates belonging to the genera Klebsiella, Sphingobacterium, and Peribacillus were isolated from the normally growing group. Two isolates (AB4 & AB15), identified as Sphingobacterium thalpophilum, were determined to be novel chlorpyrifos degraders. This is the first reported study from T & uuml;rkiye focusing on the biodegradation of chlorpyrifos by native soil bacteria. The findings revealed that various ecological areas, constitute potential sources for new microbial metabolic processes and these bacterial strains can be used in bioremediation studies.