Kimya - Metalurji Fakültesi

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http://hdl.handle.net/11527/17537

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  • Öge
    Abstract book of the international symposium on food rheology and texture, 19 October 2018 - İstanbul, Turkey
    (Istanbul Technical University Press, 2018) Kimya - Metalurji ; Lokumcu Altay, Filiz ; Toker, Ömer Said ; Dede, Sercan
  • Öge
    İTÜ Kimya Mühendisliği 1. Lisansüstü Sempozyumu Özet Kitabı 26 Nisan 2019, İstanbul
    (İTÜ, 2019-04-26) Kimya Mühendisliği ; Gümüşlü Gür, Gamze ; Genceli Güner, Fatma Elif
  • Öge
    Antifungal Activities of Different Essential Oils and Their Electrospun Nanofibers against Aspergillus and Penicillium Species Isolated from Bread
    (American Chemical Society, 2022) Karbancıoğlu Güler, Funda ; Devecioğlu, Tuğba ; Türker, Mustafa ; 0000-0001-6576-0084 ; 0000-0001-6681-0944 ; Food Engineering
    Mold growth, especially Aspergillus spp. and Penicillium spp., deteriorates the quality of bakery products. Essential oils (EOs) have been categorized as good natural antimicrobials. Hereby, this study aimed to evaluate the antifungal activity of six EOs, ginger, cumin, cinnamon, black pepper, origanum, and clove, and their volatile compounds against fungal strains isolated from bread: Penicillium carneum DDS4, Aspergillus flavus DDS6, and Aspergillus niger DDS7 by disc diffusion and disc volatilization methods, respectively. Among EOs, cumin, cinnamon, origanum, and clove were found to be effective against fungal strains, and their minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined. The observed lowest MIC value of EOs was obtained at 1000 μg/mL concentration, and the lowest MFC value was obtained from the results of clove at a concentration of 1000 μg/mL. Based on the MIC and MFC values, clove and cinnamon EOs were found to be more effective at lower concentrations. Electrospun nanofiber films of clove and cinnamon were produced with 6% poly(vinyl alcohol) (PVA), 2% β-cyclodextrin (β-CD), and 2% EO to overcome the unfavorable sensory impact of EOs on food products. The inhibitory activity of cinnamon EO film (2.64–2.51 log(CFU/mg)) was considerably lower than clove EO film (3.18–3.24 log(CFU/mg)) against P. carneum DDS4 and A. niger DDS7. Furthermore, these nanofiber films prevented fungal growth on bread samples visibly and were shown to be an alternative application for active food packaging.
  • Öge
    Simultaneous Detection of Ochratoxin A and Aflatoxins in Industrial and Traditional Red and isot Pepper Flakes along with Dietary Exposure Risk Assessment
    (American Chemical Society, 2022) Karbancıoğlu Güler, Funda ; Öztekin, Sebahat ; 0000-0001-6576-0084 ; 0000-0003-0859-1776 ; Food Engineering
    This study focused on the co-occurrence of aflatoxins (AFs) and ochratoxin A (OTA) in traditionally and industrially dried red pepper flakes (DRPFs) and isot pepper flakes (IPFs). Following the multitoxin immunoaffinity column (IAC) clean-up, high-performance liquid chromatography coupled with fluorescence detection (HPLC-FLD) was used to quantify AFs and OTA. The limit of detection (LOD) and limit of quantification (LOQ) values were 0.11 and 0.18 μg kg–1 (AFB1), 0.04 and 0.08 μg kg–1 (AFB2), 0.13 and 0.18 μg kg–1 (AFG1), 0.04 and 0.11 μg kg–1 (AFG2), and 0.10 and 0.21 μg kg–1 (OTA), respectively. AFB1, AFB2, AFG1, and OTA were found to be positive in 93, 74, 17, and 94% of all samples, respectively. The contamination levels in positive samples ranged from 0.23 to 38.69, 0.04 to 2.14, 0.13 to 0.88, and 0.18 to 52.19 μg kg–1 for AFB1, AFB2, AFG1, and OTA, respectively, while no AFG2 was found above the detection limit (0.04 μg kg–1). None of the industrial isot peppers exceeded the European Union limits, while the levels of AFB1 (5 μg kg–1), total AFs (10 μg kg–1), and OTA (20 μg kg–1) of the traditional peppers were above the limit by 30% (16/54), 26% (14/54), and 4% (2/54), respectively. Co-occurrence of AFB1-AFB2-OTA was the most frequent, accounting for 54% (29/54) of all samples. At the upper bound (UB), estimated average exposure to AFB1, total AFs, and OTA was determined to be 0.175, 0.189, and 0.124 ng kg–1 bw day–1 in all samples, respectively. The margin of exposure (MoE) value of AFB1 and total AFs was found to be 977 and 909, indicating high health concerns compared to OTA (MoE >10,000). AFB1 and total AFs may result in 0.0058 and 0.0062 liver cancer cases/100,000 person/year at UB, respectively, and weekly OTA exposure was 0.868 ng kg–1 bw, well below the provisional tolerable weekly intake, hence not of health concern. AFs exposure could endanger health, whereas OTA posed no toxicological concerns through dried red pepper consumption
  • Öge
    Recent Insights into the Use of Antagonistic Yeasts for Sustainable Biomanagement of Postharvest Pathogenic and Mycotoxigenic Fungi in Fruits with Their Prevention Strategies against Mycotoxins
    (American Chemical Society, 2023-06-23) Karbancıoğlu Güler, Funda ; Öztekin, Sebahat ; Dikmetaş, Dilara Nur ; Devecioğlu, Dilara ; Acar, Emine Gizem ; 0000-0001-6576-0084 ; Food Engineering
    Fungi-induced postharvest diseases are the leading causes of food loss and waste. In this context, fruit decay can be directly attributed to phytopathogenic and/or mycotoxin-producing fungi. The U.N. Sustainable Development Goals aim to end hunger by 2030 by improving food security, sustainable agriculture, and food production systems. Antagonistic yeasts are one of the methods presented to achieve these goals. Unlike physical and chemical methods, harnessing antagonistic yeasts as a biological method controls the decay caused by fungi and adsorbs and/or degrades mycotoxins sustainably. Therefore, antagonistic yeasts and their antifungal mechanisms have gained importance. Additionally, mycotoxins’ biodetoxification is carried out due to the occurrence of mycotoxin-producing fungal species in fruits. Combinations with processes and agents have been investigated to increase antagonistic yeasts’ efficiency. Therefore, this review provides a comprehensive summary of studies on preventing phytopathogenic and mycotoxigenic fungi and their mycotoxins in fruits, as well as biocontrolling and biodetoxification mechanisms.
  • Öge
    Effect of spray drying on physicochemical stability and antioxidant capacity of rosa pimpinellifolia fruit extract-loaded liposomes conjugated with chitosan or whey protein during in vitro digestion
    (Springer, 2024) Kasapoğlu, Kadriye Nur ; Gültekin-Özgüven, Mine ; Kruger, Johanita ; Frank, Jan ; Bayramoğlu, Pelin ; Barla-Demirkoz, Aslı ; Özçelik, Beraat ; 0000-0001-6070-4948 ; 0000-0002-2073-8075 ; 0000-0002-1810-8154 ; Gıda Mühendisliği
    Spray drying is a well-established, energy efficient, and scalable process widely used in the food industry, however it may lead to thermal degradation of susceptible compounds, such as (poly)phenols, resulting in biological activity loss to some extent. In this study, we aimed to improve the physicochemical stability and bioaccessibility of (poly)phenols from Rosa pimpinellifolia fruit extract (Rosa extract) loaded in liposomes by generating solid particles via spray drying. Liposomes were conjugated with chitosan (Ch) and whey protein (Wp) to optimize the biopolymer concentrations by monitoring mean particle diameter, polydispersity index, and surface charge. The mean diameter of liposomes ranged between 135 and 210 nm upon optimal addition of Ch (0.4%, w/v) and Wp (4.0%, w/v) which also increased the entrapment efficiency of (poly)phenols from 74.2 to 77.8% and 79.1%, respectively. After spray drying, about 65–76% of the antioxidant capacity were retained in biopolymer-conjugated liposomes (Ch or Wp) while the retention rate was 48% in only spray-dried extract (Rosa extract powder). Compared to unencapsulated Rosa extract, spray drying (Rosa extract powder) and conjugation with Ch (Ch-Lip powder) or Wp (Wp-Lip powder) significantly increased the bioaccessibility of (poly)phenols and preserved their antioxidant capacity. Based on the findings of this study, Ch- or Wp-conjugation of liposomes prior to spray drying could improve physicochemical stability and protect (poly)phenols loaded in liposomes against processing stress and passage through the digestive tract. Further in vitro and in vivo investigations on a variety of bioactive compounds may draw more attention to their potential as functional foods.
  • Öge
    Encapsulated phenolic compounds : clinical efficacy of a novel delivery method
    (Springer, 2024) Özkan, Gülay ; Ceyhan, Tuğçe ; Çatalkaya, Gizem ; Rajan, Logesh ; Ullah, Hammad ; Daglia, Maria ; Çapanoğlu, Esra ; 0000-0003-0335-9433 ; Gıda Mühendisliği Bölümü
    Encapsulation is a drug or food ingredient loaded-delivery system that entraps active components, protecting them from decomposition/degradation throughout the processing and storage stages and facilitates their delivery to the target tissue/organ, improving their bioactivities. The application of this technology is expanding gradually from pharmaceuticals to the food industry, since dietary bioactive ingredients, including polyphenols, are susceptible to environmental and/or gastrointestinal conditions. Polyphenols are the largest group of plants' secondary metabolites, with a wide range of biological effects. Literature data have indicated their potential in the prevention of several disorders and pathologies, ranging from simpler allergic conditions to more complex metabolic syndrome and cardiovascular and neurodegenerative diseases. Despite the promising health effects in preclinical studies, the clinical use of dietary polyphenols is still very limited due to their low bioaccessibility and/or bioavailability. Encapsulation can be successfully employed in the development of polyphenol-based functional foods, which may improve their bioaccessibility and/or bioavailability. Moreover, encapsulation can also aid in the targeted delivery of polyphenols and may prevent any possible adverse events. For the encapsulation of bioactive ingredients, several techniques are applied such as emulsion phase separation, emulsification/internal gelation, film formation, spray drying, spray-bed-drying, fluid-bed coating, spray-chilling, spray-cooling, and melt injection. The present review aims to throw light on the existing literature highlighting the possibility and clinical benefits of encapsulated polyphenols in health and disease. However, the clinical data is still very scarce and randomized clinical trials are needed before any conclusion is drawn.
  • Öge
    Waste to resource : surface modification of electric arc furnace flue dust by ball milling and in situ carbonization
    (Springer, 2024) Gülcan, Mehmet Feryat ; Karahan, Billur Deniz ; 0000-0002-1224-5473 ; 0000-0002-7839-2222 ; Metalurji ve Malzeme Mühendisliği
    In this article, instead of synthesizing the electrode active material using expensive precursors that lead to high carbon emissions to the atmosphere during fabrication, an alternative engineering approach is presented for the utilization of the electric arc furnace flue dust, which is an industrial waste, as anode material in lithium-ion batteries. In this scope, firstly ball milling of the flue dust with citric acid is applied and then in situ carbonization conditions are optimized by pyrolyzing the mixture at different temperatures (600 °C and 750 °C) and times (4 h and 6 h). Every sample delivers capacities greater than graphite. Structural, morphological, and chemical characterization results demonstrate that the designed method not only promotes the formation of a nanometer-thick carbon layer formation over the particles but also induces partial phase transformation in the structure. The best performance is achieved when citric acid is used as the carbon source and the ball-milled powder is treated at 600 °C for 4 h in nitrogen (C6004): It delivers 714 mAh g−1 capacity under a current load of 50 mA g−1 after 100 cycles. This research is expected to set an example for the utilization of different industrial wastes in high value-added applications, such as energy storage.
  • Öge
    Investigation of the effects of titanium oxide concentration on the sinterability, microstructural characteristics, mechanical properties, in vitro bioactivity, and cell culture behavior of chicken-derived hydroxyapatite
    (Springer, 2024) Gökçe, Hasan ; 0000-0001-7892-5642 ; Prof. Dr. Adnan Tekin Malzeme Bilimleri ve Üretim Teknolojisi UYG-AR Merkezi
    This study focuses on how titanium oxide (TiO2) in concentrations ranging from 0.5 to 4% by weight added the hydroxyapatite (CHA) made from chicken femur bones’, affects sinterability, microstructural, mechanical, and in vitro bioactivity properties. According to the results of the experiments, it was determined that CHA decomposed into whitlockite, alpha tricalcium phosphate (α-TCP), tetracalcium phosphate (TTCP), and calcium oxide (CaO) phases at different temperatures. Rutile and perovskite (CaTiO3) phases were also found in TiO2 added CHAs in addition to these phases. With increasing sintering temperature of CHA, the diameters and the heights of the samples decreased. Density increased up to 1250 °C and decreased at 1300 °C respectively. while the partial density value showed similar behavior with density and hardness, At 1200 °C, the maximum values of fracture toughness (1.071 MPam1/2) and compressive strength (145.417 MPa) were attained; however, as sintering temperatures increased, these values shifted downward to 0.882 MPam1/2 and 111.096 MPa, respectively. It has been determined that grain growth and decomposition are the underlying factors in obtaining the highest density, hardness, fracture toughness and compressive strength values for CHA at different temperatures. Among the TiO2 added CHAs, the best properties are obtained for CHA-0.5TiO2 sintered at 1300 °C (Density: 3.0057 g/cm3, Hardness: 3.973 GPa, Fracture toughness: 1.583 MPam1/2 and Compressive strength: 170.045 MPa) and the properties of the CHA-TiO2 composite decreased with increasing TiO2 ratio. This is due to the fact that increasing TiO2 has a detrimental impact on CHA’s sinterability behavior and causes it to become more porous and degrade more quickly. It was discovered through in vitro bioactivity and cell culture assays that the addition of TiO2 had a detrimental impact on the proliferation of bone tissues.
  • Öge
    Thermodynamic investigations for combustion-assisted synthesis of lithium orthosilicate powders
    (Springer, 2024) Benzeşik, Kağan ; Yücel, Onuralp ; 0000-0003-0996-5151 ; 0000-0002-3879-0410 ; Metalurji ve Malzeme Mühendisliği
    The study investigates the combustion-assisted synthesis of lithium orthosilicate (Li4SiO4) powders for potential CO2 capture applications. Technical-grade lithium carbonate and metallic silicon powders were used as starting materials. Synthesis conditions were explored across temperatures ranging from 500 to 900 °C and different holding durations. Thermodynamic modeling using FactSage 8.2 software suggested that Li4SiO4 production is feasible at temperatures of 700 °C and higher with metallic silicon as the silicon source, which was confirmed experimentally. Characterization of the synthesized powders involved X-ray diffraction, specific surface area determination, particle size distribution analysis, scanning electron microscopy, and CO2 uptake tests. Despite having the lowest Li4SiO4 content as 83.7%, the sample synthesized at 700 °C with 45 min of holding time showed the best CO2 uptake performance as 12.80 wt% while having the lowest crystallite size value (126.58 nm), the highest specific surface area value (4.975 m2/g) and the lowest average particle size value (10.85 µm) which are highly effective on the CO2 uptake performance of such solid sorbents. The study concludes that while challenges remain in achieving optimal CO2 capture performance, it lays a foundation for utilizing lithium orthosilicate in carbon capture applications.
  • Öge
    Synthesis and characterization of BaIrO3-doped YBCO superconducting thin films via TFA-MOD technique
    (Springer, 2024) Bektaş, Murat ; Birlik, Işıl ; Çelik, Erdal ; Metalurji ve Malzeme Mühendisliği
    High-temperature superconducting materials (HTS) are characterized by remarkably high critical current density (Jc) values when exposed to low temperatures and magnetic fields. In the realm of such investigations, various crystalline imperfections, including finely dispersed non-superconducting phases, dislocations, vacancies, grain boundaries, twin boundaries, antiphase boundaries, and insulating regions within grain boundaries, have been recognized as potential sources of pinning centers. However, it is essential to acknowledge that Jc values experience a rapid decline as the temperature rises in the presence of a magnetic field. The primary contributing factors to this decline are attributed to the intrinsic crystalline anisotropy of HTS materials and the thermal fluctuations that prevail at elevated temperatures. Nevertheless, a noteworthy factor in the diminishment of Jc values is the scarcity of efficacious pinning centers. In response to these challenges, a pioneering technology has emerged, revolving around nanostructure engineering for the deliberate creation of artificial pinning centers within HTS materials. In alignment with this approach, the present study endeavors to augment the critical current density and enhance the flux pinning properties of YBa2Cu3O6.56 (YBCO) superconducting films. This augmentation is achieved through the integration of BaIrO3 (BIO) perovskite nanodots, nanorods, or nanoparticles as strategically positioned pinning centers. The films are deposited on a SrTiO3 (STO) substrate employing the Trifluoroacetate Metal–Organic Deposition (TFA-MOD) technique. This research initiative seeks to contribute to the advancement of knowledge regarding the controlled manipulation of artificial pinning centers in HTS materials, particularly focusing on YBCO thin films, with the ultimate goal of enhancing their performance under the influence of elevated magnetic fields.
  • Öge
    Valorization of pineapple (ananas comosus) by-products in milk coffee beverage : influence on bioaccessibility of phenolic compounds
    (Springer, 2024) Kocakaplan, Zeynep Buse ; Özkan, Gülay ; Kamiloğlu, Senem ; Çapanoğlu, Esra ; 0009-0007-1605-6171 ; 0000-0002-6375-1608 ; 0000-0003-3902-4360 ; 0000-0003-0335-9433 ; Gıda Mühendisliği
    The industrial processing of pineapples generates a substantial quantity of by-products, including shell, crown, and core. Bromelain, a proteolytic enzyme found naturally in pineapple, including its by-products, may positively influence the bioaccessibility of phenolics from milk coffee. Therefore, this study aimed to assess how the inclusion of extracts from pineapple by-products, namely shell, crown and core, could impact the bioaccessibility of coffee phenolics when combined with milk. After measuring the proteolytic activity of pineapple by-products, the standardized in vitro digestion model of INFOGEST was employed to evaluate changes in total phenolic content, total antioxidant capacity, and individual phenolic compounds in different coffee formulations. The results showed that incorporating extracts from the crown or core in both black and milk coffee increased the bioaccessibility of total phenolics (from 93 to 114% to 105–129%) and antioxidants (from 54 to 56% to 84–87%), while this effect was not observed for the shell. Moreover, adding core extracts also enhanced the bioaccessibility of caffeoylquinic acids and gallic acid in milk coffee (from 0.72 to 0.85% and 109–155%, respectively). Overall, the findings of this study highlight that bromelain from pineapple core may have a favorable effect on the recovery of phenolic compounds in milk coffee, possibly due to its ability to cleave proteins. These outcomes point out that industrial by-products can be transformed into economic value by being reintroduced into the production process through suitable treatment instead of disposal.
  • Öge
    Tailoring hydrophobicity vs. water capacity of adsorbents for adsorption applications : role of composites
    (Springer, 2024) Atalay-Oral, Çiğdem ; Tatlıer, Melkon ; 0000-0002-8773-2348 ; 0000-0003-2792-410X ; Kimya Mühendisliği
    Water adsorption capacities of various adsorbents reported in the literature were investigated to define a hydrophobicity index that was plotted vs. water capacity. In this plot, logarithmic curves were proposed to be used as indicators of performance limits of adsorbents, especially for adsorption heat pumps. In spite of their useful adsorption properties, zeolites generally exhibited quite low hydrophobicity, remaining well below the logarithmic curve. In this study, the use of composites of zeolite NaY was examined both theoretically and experimentally for improvements in the water capacity and hydrophobicity. Salt impregnation and hydrothermal synthesis experiments were performed to prepare composites of zeolite NaY with LiCl/MgCl2 salts and activated carbon, respectively. Water capacity and hydrophobicity of zeolite NaY composites were generally superior to those of pure zeolite. Zeolite composites may be advantageous for enhancing adsorption capacity and hydrophobicity of zeolites while eliminating low stability and slow adsorption kinetics of other adsorbents. Interface between two different phases might indicate another opportunity to provide improved adsorption properties for zeolite composites.
  • Öge
    Enhancing the sustainability of Poly(lactic acid) (PLA) through ketene-based chain extension
    (Springer, 2024) Alkan Göksu, Yonca ; Metalurji ve Malzeme Mühendisliği
    The widespread utilization of nonrenewable fossil-based polymers has led to significant environmental damage. Bio-based Poly(lactic acid) (PLA) has garnered substantial academic and industrial interest in the last two decades due to its advantageous characteristics for food packaging applications. Nonetheless, the improper disposal of PLA continues to contribute to the plastic waste problem. PLA recycling mainly involves thermal processes, facing challenges due to PLA’s limited stability. This study aims to enhance PLA’s molecular weight and melt viscosity by using chain extenders to increase its degree of branching. A modular chain extender capable of thermally forming highly reactive ketene intermediates is employed to react with PLA’s hydroxyl and carboxyl end groups in a single step. For this purpose, copolymers of styrene and 2,2,5-trimethyl-5-(4-vinylbenzyl)-1,3-dioxane-4,6-dione were synthesized using free radical polymerization and characterized through 1H-NMR, TGA, and DSC analyses. The chemical interaction between these chain extenders and molten PLA was also explored, resulting in increased PLA molecular weight and higher melting temperature (Tm), reaching 155.1 for PLA_2.5CE2. Additionally, the branching introduced through this process led to a notable increase in the UV absorption of PLA, suggesting potential applications in the packaging industry. The chemical tunability of this functional ketene-based chain extender holds promise for tailoring PLA’s structure for diverse applications, further advancing its sustainability and utility.
  • Öge
    Fabrication of MIL-101(Fe)-embedded biopolymeric films and their biomedical applications
    (Springer, 2024) Kocaağa, Banu ; Bağımsız, Gamze ; Alev, İbrahim Avni ; Miavaghi, Mehran Aliari ; Sirkecioğlu, Ahmet ; Batirel, Saime ; Güner, Fatma Seniha ; Kimya Mühendisliği
    The development of wound-dressing materials with superior therapeutic effects, controlled bioactive agent release, and optimal mechanical properties is crucial in healthcare. This study introduces innovative hydrogel films designed for the sustained release of the local anesthetic drug Procaine (PC), triggered by pH changes. These films are composed of MIL-101(Fe) particles and pectin polymers. MIL-101(Fe) was chosen for its high surface area, stability in aqueous environments, and biocompatibility, ensuring low toxicity to normal cells. MIL-101(Fe)-embedded-pectin hydrogels were synthesized and characterized using Fourier-transformed infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma (ICP) spectrometry, particle size analysis, and goniometry. Rheological analysis assessed the hydrogels’ viscoelastic behavior, and UV-spectrophotometry was utilized for drug loading and release studies. The hydrogels exhibited shear-thinning properties, enhancing shape adaptability and recovery, crucial for wound-dressing applications. Controlled drug release was achieved by maintaining the PC solution’s pH between 8.2 and 9.8 during the drug-loading step. The hydrogel film’s impact on wound healing was evaluated through an in vitro wound healing assay, and cytotoxicity was assessed using a WST-1 cell proliferation assay with human dermal fibroblast cells. Results demonstrated that pectin composites enhance cell viability and support fibroblast cell migration without adverse effects, indicating their potential for effective wound healing applications. This study highlights the potential of MIL-101(Fe)-embedded-pectin hydrogels in advancing wound care technology.
  • Öge
    Cryo-assisted nitrogen treatment for the fabrication of nanoengineered, mixed transition metal oxide anode from inorganic domestic waste, for lithium-ion batteries
    (Springer, 2024) Ashraf, Humza ; Karahan, B. Deniz ; 0000-0002-7839-2222 ; Metalurji ve Malzeme Mühendisliği
    A novel method for the fabrication of nanoengineered, mixed transition metal oxide anode active material is proposed based on implementing liquid nitrogen treatment during the chemical precipitation process, for the first time in open literature. Such interference in the precipitation is believed to change the surface energy of the nuclei leading to differentiation in the growth process. To exemplify this hypothesis with an environmentally friendly approach, kitchen scourer pads, an existing waste, are used as a starting material instead of using a mixture of primary quality metals’ salts. Therefore, in this study, firstly, an optimization is realized to leach the scouring pad with 100% efficiency. Then, by applying a conventional chemical precipitation to this leachate at pH 5.5, Sample 1-P is produced. Herein, innovatively liquid nitrogen treatment is carried out during the chemical precipitation to produce Sample 2-P. Lastly, these precipitates (Samples 1-P, 2-P) are calcinated in the air to form mixed transition metal oxide powders: Samples 1 and 2, respectively. Structural, chemical, and morphological characterizations are carried out to examine the effect of liquid nitrogen treatment on the powders’ properties. To discuss the effect of nitrogen treatment on the electrochemical performances of the anode active materials (Sample 1 and Sample 2), galvanostatic tests are realized. The results show that Sample 2 demonstrates a higher 1st discharge capacity (1352 mAh/g) and retains 62% of its performance after 200 cycles when 50 mA/g current load is applied. Moreover, this electrode delivers around 500 mAh/g at 1 A/g current load. The remarkable cycle performance of Sample 2 is believed to be related to the superior chemical, structural, and physical properties of the electrode active material.
  • Öge
    Olive stone powder filled bio-based polyamide 5.6 biocomposites : biodegradation in natural soil and mechanical properties
    (Springer, 2024) Gülel, Şebnem ; Güvenilir, Yüksel ; 0000-0002-2527-5233 ; 0000-0002-1684-9055 ; Kimya Mühendisliği
    The extensive use of non-biodegradable and petroleum derived polymers in industry exacerbates environmental problems associated with plastic waste accumulation and fossil resource depletion. The most promising solution to overcome this issue is the replacement of these polymers with biodegradable and bio-based polymers. In this paper, novel biocomposites were prepared from bio-based polyamide 5.6 (PA56) with the addition of olive stone powder (OSP) at varying weight concentrations by melt compounding method. The degradability of the prepared biocomposites is investigated through soil burial test, and assessed by reduction in their mechanical properties. The biodegradability of bio-based polyamide 5.6 is shown to be improved by addition of olive stone powder, and its effects on the properties of polymer matrix are elucidated. The Fourier transform infrared (FTIR) spectrum of the biocomposites indicate the successful incorporation of OSP into PA56 polymer matrix. After six-month soil burial test, scanning electron microscopy and FTIR show the degradation of PA56 through morphological and structural changes, respectively. Differential scanning calorimetry reveals the changes in the transition temperatures of the polymer matrix and an increase in crystallinity. Thermogravimetric analysis is used on the biocomposite to determine the fraction of its components, polymer and biofiller, and the results show that 2.67% (w/w) of the polyamide 5.6 is biodegraded at the end of the six-month soil burial.
  • Öge
    Identifying and assessing putative allosteric sites and modulators for CXCR4 predicted through network modeling and site identification by Ligand Competitive Saturation
    (American Chemical Society, 2024) İnan, Tuğçe ; Flinko, Robin ; Lewis, George K. ; MacKerell, Alexander D., Jr. ; Kürkçüoğlu, Özge ; 0000-0001-8287-6804 ; 0000-0003-0228-3211 ; Kimya Mühendisliği
    The chemokine receptor CXCR4 is a critical target for the treatment of several cancer types and HIV-1 infections. While orthosteric and allosteric modulators have been developed targeting its extracellular or transmembrane regions, the intramembrane region of CXCR4 may also include allosteric binding sites suitable for the development of allosteric drugs. To investigate this, we apply the Gaussian Network Model (GNM) to the monomeric and dimeric forms of CXCR4 to identify residues essential for its local and global motions located in the hinge regions of the protein. Residue interaction network (RIN) analysis suggests hub residues that participate in allosteric communication throughout the receptor. Mutual residues from the network models reside in regions with a high capacity to alter receptor dynamics upon ligand binding. We then investigate the druggability of these potential allosteric regions using the site identification by ligand competitive saturation (SILCS) approach, revealing two putative allosteric sites on the monomer and three on the homodimer. Two screening campaigns with Glide and SILCS-Monte Carlo docking using FDA-approved drugs suggest 20 putative hit compounds including antifungal drugs, anticancer agents, HIV protease inhibitors, and antimalarial drugs. In vitro assays considering mAB 12G5 and CXCL12 demonstrate both positive and negative allosteric activities of these compounds, supporting our computational approach. However, in vivo functional assays based on the recruitment of β-arrestin to CXCR4 do not show significant agonism and antagonism at a single compound concentration. The present computational pipeline brings a new perspective to computer-aided drug design by combining conformational dynamics based on network analysis and cosolvent analysis based on the SILCS technology to identify putative allosteric binding sites using CXCR4 as a showcase.
  • Öge
    Melt rheological and bead foaming behavior of recycled polyethylene terephthalate/polybutylene terephthalate blends modified with a joncryl chain extender
    (American Chemical Society, 2024) Akdevelioğlu, Yavuz ; Himmelsbach, Andreas ; Ruckdäschel, Holger ; Nofar, Mohammadreza ; 0000-0002-8917-7990 ; 0000-0001-5985-2628 ; 0000-0002-4364-2930 ; Metalurji ve Malzeme Mühendisliği
    This study investigates the melt rheological properties and foamability of recycled polyethylene terephthalate (rPET) and its blends with polybutylene terephthalate (PBT) modified through an epoxy-based Joncryl ADR 4468 chain extender. A twin-screw extruder was used to prepare rPET/PBT blends at various weight ratios (i.e., 100/0, 75/25, 50/50, 25/75, and 0/100) and with varying Joncryl chain extender contents (i.e., 0.25, 0.5, 0.75, and 1.0 wt %). The small-amplitude oscillatory shear rheological experiments were conducted to analyze the melt viscoelastic behavior of the samples. The melt strength and strain-hardening behavior of the compounds were examined by measuring the extensional rheology and Rheotens tests. Crystallization analysis was conducted on the processed samples by using differential scanning calorimetry. The bead foaming behavior of the samples was investigated using a batch-based foaming reactor with supercritical CO2. Both compounding with PBT and Joncryl chain modification increased the complex viscosity, melt strength, and strain-hardening behavior of the blends, while their synergistic effect revealed a more noticeable enhancement. Although direct modification of rPET with Joncryl and its direct compounding with PBT could not generate a meaningful foam structure, a homogeneous microcellular foam structure could successfully be induced when 25 wt % rPET was incorporated in blends with PBT modified with 1.0 wt % Joncryl.
  • Öge
    Alternative plant-based gluten-free sourdough pastry snack production by using beetroot and legumes: characterization of physical and sensorial attributes
    (American Chemical Society, 2024) Yolcu, Zeynep ; Demircan, Evren ; Mertdinç, Zehra ; Aydar, Elif Feyza ; Özçelik, Beraat ; 0000-0002-1810-8154 ; Gıda Mühendisliği
    Objective of this study was to design a formula of a sourdough pastry snack by adding starter inoculum into the formulation which was obtained by the fermentation process through beetroot (Beta vulgaris) puree with black-eyed pea (Vigna unguiculata) and fava bean (Vicia faba). With this development process, it was aimed to review the functional impact of legumes as gluten replacement and emphasize the importance regarding physical and sensory attributes in a pastry snack product. First, a starter inoculum was developed based on modification of the shalgam fermentation process with legumes. An experimental design suggested by the response surface methodology was used to optimize its microbial properties and level of antioxidants with the factors of amounts of beetroot puree, fava bean/black-eyed pea ratio, and fermentation time. In the second part, this starter inoculum was mixed with fava bean flour to obtain a sourdough pastry snack (FBS) with improved physical and sensory attributes and compared to the wheat control sourdough (WCS) pastry snack after the baking process. According to the optimization results to produce starter inoculum with the optimum results of lactic acid bacteria 9.55 log cfu/mL, the level of antioxidant activity 91.86 μM TE/mL, and total yeast level 6.96 log cfu/mL; 75 mL of beetroot puree, 100% for fava bean, and fermentation for 24 h were obtained. Compared to WCS, FBS has approximately 16% higher hardness values. Also, a significant difference was observed for stiffness and springiness among samples. The retention of moisture was higher in the first 4 days following the storage for 8 days; the moisture content continuously decreased with the final moisture content of 12.6%. When compared with the results of textural profile analysis in terms of hardness, stiffness, and springiness, sensory results were correlated. Comparing the overall acceptability of the FBS to WCS, FBS was from moderate to higher scores, which indicated that it could be a promising alternative to chemically developed snack products and a preferred product for people suffering from celiac disease and other gluten intolerances.