Browsing by Author "Yardim, Dilek Ozcan"

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Identification of Antihypertensive Bioactive Peptides in the Herby and White Cheeses Produced From Different Milk Types
(Springer, 2023) Yardim, Dilek Ozcan; Durak, Muhammed Zeki
The primary objective of this study was to identify bioactive peptides with ACE inhibitor activity in Van herby cheeses and white cheeses made from various milk types. The types of milk used to produce ripened white and Van herby cheeses were cow, sheep, and goat milk. All types of milk were pasteurized, and the starter culture (the mixing of Lc. lactis subsp. cremoris and Lc. lactis subsp. lactis) was added. In all the cheeses, samples were taken for dry matter, pH, and protein analysis on the 0th, 90th, and 180th days of ripening. Fragments were identified using the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) method, which were derived from casein hydrolysis, as well as other cheese peptides and proteins. An ACE inhibitor effect was observed in the range of 8.79%-11.54% in the tested cheese samples after 180th day of ripening. The bioactive peptides were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In the cheese samples, nine ACE inhibitor peptides originating from casein were detected using LC-MS/MS. Observations indicated that cheeses ripened for longer durations had an increased number of bioactive peptides, demonstrating potential positive impacts on human health and suggesting their possible use in functional foods or dietary supplements.
Isolation and Characterization of Endophytic Bacteria From the Poaceae Family: Assessing Their Impact on Drought Stress and Plant Growth in Wheat
(Springer, 2025) Akkopru, Ahmet; Taskin, Bilgin; Arpali, Digdem; Ucar, Ceylan Pinar; Yardim, Dilek Ozcan; Ozturkci, Yusuf
Limited water resources and the increasing impact of global warming highlight the importance of endophytic bacteria (EB) given their unique tolerance to drought stress. In this study, we isolated EB from cultivated and wild Poaceae family members grown in arid or challenging environments in Lake Van Basin. We aimed to reveal plant growth promoting (PGP) characters in EB and to determine their potential to promote plant growth and reduce the effect of different drought levels in two different wheat cultivars (Tir (tolerant) and Bezostaja-1). 410 EB were isolated from 135 plants belonging to 19 taxa at different periods. In vitro tests revealed that 73.1% of the isolates can synthesize indole acetic acid (IAA), 34.4% can fix nitrogen, 37% can synthesize 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCd), 37.6% can solubilize phosphorus, and 93.9% can synthesize siderophore. IAA production and phosphorous solubility were the most common characters, coexisting in 59% of EBs. ACCd production, phosphorus solubilization, and nitrogen fixation were the most common features with a triple association of 0.49%. Although isolates selected according to EB characters showed differing effects on coleoptile, root and shoot length, germination percentage, shoot and root weight, and relative water content (RWC) in the early development period (EDP) of Bezostaja-1 cultivar under drought stress, some isolates had negative effects. However, Pseudomonas asturiensis G58S1, Pantoea agglomerans G129K1-1, Chryseobacterium rhizosphaerae G129S2, Acinetobacter calcoaceticus G118K1T, and Stenotrophomonas sp. G109K2-K isolates selected according to PGP trials and EDP results showed improved plant biomass, chlorophyll content, membrane permeability, germination power, and RCW, and protective effects against drought.
The Voltammetric Determination and Electrochemical Mechanism of Alpha-Lipoic Acid at a Multi-Walled Carbon Nanotube-Surfactant Modified Glassy Carbon Electrode in the Food Additive Sample
(Springer, 2024) Yardim, Dilek Ozcan; Pinar, Pinar Talay
Alpha-lipoic acid (alpha-LA) is a naturally occurring compound that is both water and fat soluble, functioning as a powerful antioxidant in the body. In this study, multi-walled carbon nanotubes (MWCNTs) with SDS were electrodeposited onto a glassy carbon electrode (GCE) electrochemically. This modified electrode was characterized by electrochemical techniques (EIS, CV). The MWCNT/SDS-modified GCE was utilized for the analysis of alpha-LA. An electrochemical oxidation mechanism for alpha-LA was proposed using the developed electrochemical sensor. After optimizing the conditions, the MWCNT/SDS-GCE sensor exhibited a linear response in the concentration range of 0.6-9.0 mu M, with a detection limit of 0.15 mu M. Additionally, this chemical sensor was effectively utilized for the electrochemical analysis of alpha-LA in the food additive sample.