Özkan, Altan
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Oezkan, A.
Ozkan, A.
Ozkan, Altan
Özkan, A
Özkan, A.
Ozkan, A
Oezkan, Altan
Ozkan, A.
Ozkan, Altan
Özkan, A
Özkan, A.
Ozkan, A
Oezkan, Altan
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Email Address
altanozkan@iyte.edu.tr
Main Affiliation
03.07. Department of Environmental Engineering
Status
Current Staff
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Sustainable Development Goals
1NO POVERTY
0
Research Products
2ZERO HUNGER
2
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3GOOD HEALTH AND WELL-BEING
0
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4QUALITY EDUCATION
0
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5GENDER EQUALITY
0
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6CLEAN WATER AND SANITATION
3
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7AFFORDABLE AND CLEAN ENERGY
2
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8DECENT WORK AND ECONOMIC GROWTH
1
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
3
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10REDUCED INEQUALITIES
0
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11SUSTAINABLE CITIES AND COMMUNITIES
0
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12RESPONSIBLE CONSUMPTION AND PRODUCTION
2
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13CLIMATE ACTION
3
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14LIFE BELOW WATER
2
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15LIFE ON LAND
1
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16PEACE, JUSTICE AND STRONG INSTITUTIONS
0
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17PARTNERSHIPS FOR THE GOALS
0
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Documents
22
Citations
910
h-index
11
Documents
19
Citations
781
Scholarly Output
8
Articles
3
Views / Downloads
2123/1654
Supervised MSc Theses
4
Supervised PhD Theses
0
WoS Citation Count
7
Scopus Citation Count
6
Patents
0
Projects
3
WoS Citations per Publication
0.88
Scopus Citations per Publication
0.75
Open Access Source
2
Supervised Theses
4
| Journal | Count |
|---|---|
| Algal Research | 1 |
| Algal Research-Biomass, Biofuels and Bioproducts | 1 |
| Phycoremediation of Wastewater: Practical Applications for Sustainability | 1 |
| Turkish Journal of Botany | 1 |
Current Page: 1 / 1
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8 results
Scholarly Output Search Results
Now showing 1 - 8 of 8
Master Thesis Co-Production of Chitin Nanofibers, Proteins, and Lipids in Marine Diatoms Belonging To the Thalassiosira Genus(Izmir Institute of Technology, 2022) Sezgin, Tuğçe; Özkan, Altan; Özkan, AltanChitin is a biopolymer used in various industries, including biomedical, pharmaceutical, medical, and food. Today, the vast majority of chitin is obtained from waste shellfish. Shellfish chitin has an inherent impurity problem because chitin in these organisms is embedded in other organics and inorganics. Thus, new sources have been investigated. Diatoms, particularly Thalassiosira and Cyclotella species, have the potential to be the providers for applications requiring high quality through their unique ability to biosynthesize and extrude chitin nanofibers. The primary aim of this study is to study this potential. This investigation entailed the cultivation of three Thalassiosira strains according to a standard cultivation protocol under photobioreactor conditions. The secondary aim was to assess the possibility of commercially valuable co-product generation. For this, biomass protein, lipid, and fatty acids contents were analyzed. Chitin productivity varied significantly between the strains. The peak productivities and final concentrations ranged from 4 to 25 mg/L-day and from 60 to 250 mg/L, respectively. Average fiber diameters ranged from 68.5 to 95.0 nm. Silicon limited growth increased the chitin biosynthesis in T.weissflogii 1336 and T.pseudonana 2135. Biomass lipid contents of over 45% were obtained with T.pseudonana 2135 under silicon depletion. The fatty acid profiles indicated the suitability for application as live aquaculture feed for T.weissflogii 1336, and biodiesel feedstock material for T.pseudonana 2135. The highest biomass protein contents were about 30%, which were obtained under silicon availability. This study, for the first time, assessed the chitin productivity of Thalassiosira strains and demonstrated unique multiproduct generation scenarios.Article Citation - WoS: 5Citation - Scopus: 5Screening Diatom Strains Belonging To Cyclotella Genus for Chitin Nanofiber Production Under Photobioreactor Conditions: Chitin Productivity and Characterization of Physicochemical Properties(Elsevier, 2023) Özkan, AltanDiatom species belonging to Cyclotella and Thalassiosira genera have the unique and industrially relevant ability to biosynthesize and extrude pure chitin nanofibers. The current understanding of diatom-based chitin production is narrowed by the complete reliance on the performance of a single strain. This study aims to facilitate the development of a wider understanding for enhanced industrial utility. For this purpose, six Cyclotella strains were cultivated under standardized process conditions of a bubble column photobioreactor, and the resulting productions were characterized in terms of rate and physicochemical properties. A two-stage cultivation protocol was followed where the cells were cultivated under silicon replete and then following its complete consumption under silicon deplete conditions. All the strains produced chitin fibers of β-form with relatively constant average diameters, ranging from 48 to 58 nm. Chitin production rates and final concentrations as well as fiber number densities and length distributions were highly strain-dependent. Dissolved silicon availability controlled chitin biosynthesis: following its depletion, the productivity of all the strains increased drastically. Two strains of marine origin, C. cryptica CCMP 332 and C. cryptica CCMP 333, generated the most favorable outcomes for commercial-scale production and had final concentrations of 272 ± 9 mg/L and 316 ± 12 mg/L, and maximum production rates of 48 ± 2 mg/L-day and 51 ± 2 mg/L-day, respectively. The superior performance of these strains was due to (i) the extrusion of more fibers per fiber port, in the case of C. cryptica CCMP 333 as many as 20.7 ± 1.0. indicating free fiber accumulation in suspension, and (ii) the biosynthesis of longer fibers, mean fiber lengths varied from 15 to 20 μm during cultivation. This study demonstrates the importance of species selection and silicon availability for diatom-based chitin production in terms of rate, final concentration, and nanofiber fiber length distributions.Article Effects of Cultivation Temperature on Protein Production of Selected Spirulina Strains Under Photobioreactor Conditions(Elsevier, 2026) Binkanat, Tahir Burak; Ozkan, AltanSpirulina is cultivated industrially for food supplement applications due to its high protein content and protein quality. This study assessed the influence of cultivation temperature on the productivity of widely accessible, protein-rich Spirulina strains under standardized bubble column photobioreactor conditions, with the goal of identifying strains with consistently high nutritional value across varying temperatures and culture age for outdoor applications. Five strains were first screened for protein content at 30 degrees C, and three with protein contents >60 % dry biomass were selected for cultivation at 25 degrees C, 35 degrees C, and 40 degrees C. Protein content was measured daily to determine variations, and protein quality was assessed at log and stationary growth phases. The metal content was analyzed to assess the toxic heavy metal bioaccumulation potential. At the optimum temperature of 35 degrees C, the strains had similar biomass productivities. However, the protein contents were highly temperature and strain-specific. Based on the strain, under identical process conditions, a relatively stable protein content of around 65 % or a content variation from 30 to 70 % was observed through the cultivation. Growth at 25 degrees C lowered the biomass productivity without affecting the protein contents, and growth at 40 degrees C lowered both parameters. S. platensis UTEX 2340 had consistently the highest protein quality, reflected by its higher cumulative essential amino acid contents and essential amino acid index scores. However, at 35 degrees C, the strain also had a mercury content exceeding the safety limits set for food supplements. These findings demonstrate the importance of strain selection and cultivation temperature in maintaining the nutritional value of Spirulina-based products.Book Part Algal Biofilm and Phycoremediation(CRC Press, 2024) Güneş, K.; Kaplangı, B.B.; Özkan, A.; Kucuker, M.A.Various physical and chemical methods have been extensively studied and explored for the remediation of heavy metals, pesticides, and other contaminants present in wastewater. However, the chemicals used in these methods lead to a second treatment, causing problems such as high cost and application difficulties. To overcome this problem, the bioremediation method is an acceptable pollutant removal alternative. It is used as an efficient biological agent in bioremediation studies in microalgae and bacterial strains commonly used in treatment systems. Phycoremediation refers to microalgae-based pollutant removal. In recent studies with algal bioremediation, Chlorella sp., Scenedesmus sp., Spirulina platensis, and Chlamydomonas sp. have been used mostly to remove organic and inorganic pollutants from water streams. In this section, definitions regarding algal biofilm, including its formation mechanism and applications in remediation, will be provided. Subsequently, the suspended and attached algal growth systems commonly employed for pollutant removal will be studied. Furthermore, diverse methodologies utilized for the valorization of algal biomass will be examined. © 2025 selection and editorial matter, Maulin P. Shah and Günay Yıldız Töre.Article Citation - WoS: 2Citation - Scopus: 1Dynamics of Co2 Consumption, and Biomass and Lipid Carbon Production During Photobioreactor Cultivation of the Diatom Cyclotella(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2023) Ökten, HaticeUnderstanding of CO2 delivery and consumption dynamics in algal photobioreactors are critical to unravel microalgae’s full potential for bioproduct generation and carbon capture from flue gas streams. This study aims to expand our current understanding by cultivating the diatom Cyclotella under controlled process conditions of a bubble column photobioreactor and analyzing CO2 consumption dynamics in real time using results from an online CO2 sensor connected to the reactor exhaust. Two sets of experiments were conducted: they served to contrast the influence of silicon and nitrate (Si&N colimitation) and Si limitation, and the light availability, respectively. CO2 consumption was calculated based on the mass balance around the reactor inlet and outlet gas streams. Biomass samples and lipid extracts were analyzed for carbon (C) content to determine biomass-C and lipid-C concentrations. The outlet CO2 concentrations varied significantly with cultivation time and process conditions. More than 15% to 65% of the CO2 introduced left the reactor in the exhaust at any instance based on the set CO2 transfer rates. The highest average daily capturing efficiency was 60%. Nutrient limitation regimes imposed generated unique CO2 consumption profiles undiscernible by the biomass-C analysis, i.e. unlike Si limitation, N limitation had more immediate detrimental effects on C consumption. Final biomass-C concentration increased with increasing N and light availability, 275 mg/L vs. 336 mg/L, and 270 mg/L vs. 501 mg/L, respectively. Biomass-C based capturing efficiency approximations resulted in 20% to 40% underestimation. Under Si-limited conditions, the higher light intensity increased the final lipid-C to biomass-C ratio by two times (from 20% to 40%) and the final lipid-C concentration and peak productivity by four times (from 56 mg/L to 216 mg/L, from 7 to 30 mg/L-day, respectively). This study demonstrates online exhaust CO2 concentration-based analysis’s unique capabilities for assessing carbon availability and capture, organic-C production, and its diversion to biomass and lipid production.Master Thesis Screening Spirulina Stranins for Protein Productivity Based on Cultivation Under Photobioreactor Conditionsy(01. Izmir Institute of Technology, 2022) Binkanat, Tahir Burak; Özkan, Altan; Büyükkileci, Ali OğuzSpirulina is an industrially produced algae for consumption as a nutritional supplement owing to its exceptionally high protein content. The delivery of the desired metabolite profiles highly depends on selecting the correct strains for growth. In this regard, the information in the literature is limited as the strains cultivated industrially are unknown, and the strains of academic research were mostly locally isolated or procured from local sources. The current study is the first step of research activities planned to assess the large-scale production potential of Spirulina in Izmir. Thus in this work, Spirulina platensis 2340, Spirulina maxima 84.79, Spirulina platensis 85.79, Spirulina platensis 86.79, and Spirulina platensis 29 were screened for biomass and protein productivity during cultivation under standardized process conditions of a bubble column photobioreactor. The final biomass concentrations were strain specific and ranged from 1.2 to 1.9 g/L. An inverse relationship existed between the logistic model-based final biomass concentrations and the production rate constants. Thus, the peak productivities were more evenly distributed and ranged between 0.15 to 0.20 g/L-day. SP 29 had the ideal protein content vs. cultivation time profile as it was consistently high and varied in the narrow range of 60 to 64%. Higher protein contents could be reached with the other strains, but they also had higher variations during the growth period. The final protein concentrations varied from 0.4 g/L to 1.4 g/L. The highest peak productivity obtained was about 0.11 g/L-day, which could be obtained by three of the strains. The results clearly show the importance of strain selection for sustaining protein-rich biomass production with Spirulina.Master Thesis Investigation of Phosphate Recovery From Anaerobic Digestate(01. Izmir Institute of Technology, 2024) Erünsal, İlker; Bayrakdar, Alper; Özkan, AltanFosfat, tarım sektöründe nutrient kaynağı olarak yaygın olarak kullanılan nadir ve yenilenemeyen bir kaynaktır. Fosfatın büyük çoğunluğu madencilik faaliyetlerinden elde edilir. Bunlar göz önüne alındığında, sıvı atıklardan fosforun geri dönüşümü, alternatif ve sürdürülebilir bir kaynak olarak görülebilir. Organik atıkların anaerobik çürütülmesi, fermente ürün adı verilen fosfor açısından zengin bir atık üretir. Bu çalışmanın amacı bu fosfat geri kazanımı potansiyelini incelemektir. Bunun için adsorpsiyon yöntemi ve strüvit çöktürme yöntemi araştırılmıştır. Adsorpsiyon potansiyelleri göz önüne alınarak iki farklı atık maddeden ZnCI2-FeCl3.6H2O ile modifiye biyokömür üretilmiştir. Karşılaştırmalı testler, Mısır Koçanı Biyoçarının (Fe-BC-C) 33 mg/g fosfat adsorpsiyon kapasitesine ulaşırken, Atık Anason Biyoçarının (Fe-BC-A) 41 mg/g'a ulaştığını göstermiştir. Biyoçarlar ile P salınımı ve kontrol deneylerinde her iki biyoçarın da ortama fosfor saldığı ve düşük adsorpsiyon potansiyeline sahip olduğu gözlemlenmiştir. Bu durum, fosfor geri kazanımı için modifikasyon sürecinin önemini göstermiştir. Strüvit çökelmesi laboratuvar ölçekli kolonda ve pilot ölçekli kolonda MgCl2.6H2O ilavesiyle araştırılmıştır. Her iki sistemde de %80'den fazla fosfor geri kazanımı gözlemlenmiştir. Fosfat giderimini etkileyen parametreler pH, Mg/P molar oranı, yukarı akış hızı, reaktör tipi ve sürekli besleme olarak belirlenmiştir.Master Thesis The effects of photobioreactor average shear rate on chitin nanofiber production characteristics of the diatom cyclotella cryptica(01. Izmir Institute of Technology, 2024) Ağaoğlu, Cemre; Özkan, Altan; Yılmaz, Benay UzerKitin biyomedikal uygulamalar açsıından çok yüksek potansiyelli doğal bir biyopolimerdir. Halihazırda, ticari kitin üretiminin çoğunluğu deniz ürünleri endüstrisi tarafından işlenen kabuklu deniz canlılarının atıkları kullanılarak yapılmaktadır. Diatom cinslerinden Cyclotella ve Thalassiosira kitin nanofiberlerini direkt olarak hücre duvarları üzerinde bulunan fultoportula adı verilen açıklıklardan dış ortama sentezleyebildikleri için kitin hasatı için sert ektraksiyon koşulları uygulanması gerekliliğini ortadan kaldırmaktadır. Bu çalışmada, Cyclotella cryptica CCMP 333 hücrelerinin kitin üretkenliğinin kabarcık kolon fotobiyoreaktörün havalandırma hızındaki farklılıktan kaynaklı maruz kaldıkları hidrolik kesme kuvvetinden nasıl etkilendiği iki aşamalı bir kültivasyon protokolü (birinci aşamada 0,020 mM silikon takviyesini müteakiben ikinci aşamada 1,80 mM silikon takviyesi) uygulanarak araştırılmıştır. Hücrelerin silikon starvasyonuna maruz bırakıldığı birinci aşamada havalandırma hızı 0,5 vvm olarak sabit tutulmuştur, 1,80 mM silikon takviyesinin ardından havalandırma hızlarının 0,25 vvm, 1 vvm ve 1,5 vvm olarak değiştirildiği 3 ayrı fotobiyoreaktör düzeneği kurulmuştur. Bu çalışma kapsamında ulaşılan maksimum kitin üretkenliği 852 mg/L olmuştur ve bu konsantrasyona silikon starvasyon aşamasında 0,5 vvm ile havalandırılan ve ardından 1,8 mM silikon takviyesi ile eş zamanlı olarak havalandırma hızının 1 vvm olarak değiştirildiği deney grubunda saptanmıştır. Cyclotella cryptica CCMP 333 hücre süspansiyonlarında serbest olarak ve hücreye bağlı olarak buluna kitin konsantrasyonları durağan faz sürecinde toplanan numuneler kullanılarak belirlenmiştir. Hücreye bağlı kitin nanofiberlerin konsantrasyonu ile havalandırma akış hızları arasında ters orantı olduğuna dair elde edilen sonuçlar büyük ölçekli diatom üretim tesislerinde hasatlanacak kitin nanofiberi miktarının maksimizasyonu için geliştirilecek stratejilere katkı sağlayacaktır.