Phd Degree / Doktora

Permanent URI for this collectionhttps://hdl.handle.net/11147/2869

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Author: search.filters.author.Sofuoğlu, Aysun

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  • Doctoral Thesis
    Estimation of Exposure To Persistent Organic Pollutants and Associated Health Risks
    (01. Izmir Institute of Technology, 2024) Genişoğlu, Mesut; Genişoğlu, Mesut; Sofuoğlu, Aysun; Sofuoğlu, Sait Cemil; Sofuoğlu, Sait Cemil; Sofuoğlu, Aysun
    Kalıcı Organik Kirleticiler (POPs), çevresel bozunmaya karşı dirençli, uzun mesafeler boyunca taşınabilen ve organik maddelere olan yüksek afiniteleri nedeniyle çevresel ortamlarda ve gıda zincirinde biriken, küresel olarak yaygın maddeler oldukları için insan sağlığı açısından önemli riskler oluşturur. Pertikül ve hava, toprak ve hava, sedimen ve su arasında dağıldıkları için tarım ürünlerinde, etlerde ve deniz ve tatlı su ürünlerinde bulunurlar. Bu da yutma, soluma ve deri teması yoluyla maruziyete ve sağlık risklerine yol açar. Sonuç olarak, mümkün olduğunca çok sayıda POP grubunu araştırmak için kapsamlı bir tarama çalışması tasarlanmıştır. İzmir'de rastgele seçilen ev ve okullardan, iç ve dış mekan havasıyla beraber çökelmiş toz ve yemek örnekleri toplanmıştır. Ayrıca, kafe/bar/restoranlardan iç mekan çökelmiş toz örnekleri toplanmıştır. Örnekler hazırlık, ekstraksiyon ve temizleme işleminden geçirildikten sonra, PAH'lar, PCB'ler, PBDE'ler, NBFR'ler ve OPFR'lerin hedef bileşikleri GC/MS cihazıyla analiz edilmiştir. Ölçülen konsantrasyonlar ve toplanan maruziyetle ilgili anket bilgileri, USEPA maruziyet-risk modellerine girdi değişkenleri olarak kullanılarak yutma ve soluma maruziyetlerini (kronik günlük alım) Monte Carlo yöntemi kullanılarak ilgili sağlık riskleri simüle edilmiştir. Örnekleme yerleri, kentleşmenin etkisini araştırmak için kırsal, banliyö, kentsel alanlar ve bir sanayi bölgesinin rüzgaraltı yerleri arasında mekansal olarak dağıtılmıştır. Bu tez çalışması kapsamında, küresel literatüre girmiş çalışmalar arasında çevresel ve gıda örneklerinde analiz edilen bu kadar yüksek sayıda hedef POP bileşiği düzeyleri konusunda bilgi veren en kapsamlı veriseti oluşturulmuştur.
  • Doctoral Thesis
    Phthalate Esters Degradation Mechanisms by Enzymes
    (01. Izmir Institute of Technology, 2023) Balcı, Esin; Sofuoğlu, Aysun; Mohamed, Gülşah Şanlı
    Phthalate esters (PAEs) stand out as the priority toxicants due to their carcinogenic, mutagenic, and teratogenic properties. The enzymatic degradation is hailed for its recognized safe and environmentally friendly properties. This study delved into PAEs' degradation, especially dibutyl phthalate (DBP) and diethylhexyl phthalate (DEHP) by recombinant esterase from Geobacillus sp. isolated from Balçova Geothermal region in İzmir. The esterase exhibited efficient degradation of DBP but had limited effectiveness in degrading DEHP. Many experiments were conducted to compare the ability of recombinant esterase to degrade DBP and DEHP with that of commercially available enzymes secreted from various microorganisms. Among these enzymes, Bacillus subtilis esterase and Rhizomucor miehei lipase had the highest ability. They were immobilized on halloysite nanotubes (HNTs) by adsorption method to enhance their stability and prolong their activity in applications. To investigate the impact of immobilization methods, two bionanocomposites were formed by immobilization of Bacillus subtilis esterase to HNTs with chitosan (CTS) and alginate (ALG) by the cross-linking method. Two fixed-bed reactors with CTS-HNT-EST and ALG-HNT-EST were operated in batch and continuous modes for PAEs' degradation. CTS-HNT-EST exhibited superior efficacy and durability in PAEs' removal for both modes. Lastly, bioremediation experiments were conducted in PAEs-contaminated soils using Bacillus subtilis esterase and recombinant esterase. Although both esterase had the same active site triad, recombinant esterase had a less significant effect on PAEs' degradation. This fact can be attributed to different substrate specificity and enzyme dynamics. Despite variations in their degradation capabilities, both commercial and newly engineered recombinant enzymes demonstrate considerable potential for breaking down PAEs.
  • Doctoral Thesis
    Long-Term Protection Efficiency of Biodegradable Polymer Treatments on Limestone
    (Izmir Institute of Technology, 2019) Kaplan, Zişan; Böke, Hasan; Sofuoğlu, Aysun; İpekoğlu, Başak
    Synthetic polymers can be replaced by biodegradable ones as adhesive, water repellents and consolidants in stone conservation to preserve historic buildings from further deterioration. In this study, the long-term stabilities of two biodegradable polymers, polyhydroxybutyrate (PHB) and poly-l-lactide (PLA) and an acrylic polymer (Paraloid B72), which are commonly used in conservation works of artefacts, were evaluated on limestone through an UV lamp-weathering chamber. Chemical and morphological changes induced by accelerated weathering test were followed by Fourier Transform Infrared spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM) analysis. The protection efficiencies of the polymers were determined by following the changes in the color, capillary water absorption and static contact angle on the limestone surfaces in accordance with CEN standards developed by the European Committee of Standardization (CEN) for conservation of cultural property. PHB, PLA and Paraloid B72 coatings significantly increased hydrophobicity, decreased capillary water absorption and caused negligible change in the color of the limestone. All polymers showed chemical, physical and optical changes under accelerated weathering conditions. Paraloid B72 decomposed by the reduction of molecular weight, decomposition of ester group and formation of gamma lactones and hydro peroxides. PHB and PLA decomposed with formation of CO2 and hydro peroxide, hydrolysis of ester groups and reduction of the molecular weight. Chemical changes cause to etching, holes, voids, cracks and slight color differentiations on the coatings by chain scission, breaking of polymer bonds and formation of volatile gaseous products. Protection efficiencies of the PLA and PHB polymers almost same as that of the widely used acrylic polymer Paraloid B72. However, PLA and PHB seem to be promising polymers as protective agents due to their reversibility and biodegradability, low chromatic changes, good hydrophobic behavior and good stability to weathering in reducing the effects of outdoor exposure on limestone surfaces.
  • Doctoral Thesis
    Use of Bio-Nano Composites as Protective Coating on Natural Stone Surfaces
    (Izmir Institute of Technology, 2013) Ocak, Yılmaz; Sofuoğlu, Aysun
    Historical monuments are important heritages to pass cultural values to next generations. Most of the historical monuments were composed of natural stones like marble. SO2 and NOx reacts with marble composed primarily of calcite (CaCO3) is a dry deposition process, gypsum (CaSO4.2H2O) and nitrocalcite (Ca(NO3)2.4H2O) are formed after reaction. The polylactic acid (PLA), 2, 5 and 7 wt.% montmorillonite (MMT) clay added PLA (PLA/MMT2, PLA/MMT5 and PLA/MMT7) bio-nano composites coated and uncoated surfaces were tested for capillary water absorption, water vapor permeability, color alteration, and surface hydrophobicity regarding the nanofiller concentrations before reaction. Results indicated that the bio-nano composite coatings didn’t alter the color of the marble, improved the hydrophobicity and barrier properties of the marbles. The level of layered silicate delamination in the PLA matrix and structural characterizations of PLA nanocomposite coatings were affected the barrier properties of the composites coatings. The X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM) analysis pointed out that 5% layered silicates were homogenously dispersed in the polymer matrix, exfoliated structures also were observed in some parts of the polymer matrix and nano particles enhanced the nano-composite coating barrier performance. The protection capabilities of the bio-nano composite coatings were studied in laboratory setup (include nearly 8 ppm SO2) and ambient city atmosphere (include nearly 8 ppb SO2 and 64 ppb NO2). The PLAMMT5 bio-nano composite showed significant reduction (~5 times) in the crust formation after 180 days SO2-calcite reaction in laboratory and 9-10 times after 20 months ambient city exposures for outdoor conditions. Bio-nano composites also decreased the kinetic parameters such as rate constant (ks) and effective diffusivity (De) values of the marbles. These results indicated that PLA/MMT bio-nano composite coating seems to be significant promising materials as protective coating agents in reducing the effects of atmospheric pollutants on the marble surfaces.