Browsing by Author "Demirel Z."
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Item Enhanced microalgal lipid production in internally illuminated airlift photobioreactor(Marine Technology Society Inc., 2019) Deniz I.; Demirel Z.; Imamoglu E.; Dalay M.C.Internal illumination systems are being considered for use as an alternative light supply technique in microalgal products. The main goal of the study was to analyze the roles of different light wavelengths in internally illuminated airlift photobioreactors (PBRs) providing the light energy in an efficient way for the biomass production, lipid yield, and fatty acid composition of Amphora capitellata. The maximum chlorophyll-a concentration per unit biomass (2.62 ± 0.16 mg L-1) was obtained under red light, which was only 14% higher than under blue light in internally illuminated airlift PBR, whereas low chlorophyll-a content was found under white light. Maximum specific growth rate of 0.317 day-1, which corresponded to a doubling time of 2.185 days, was obtained under red light for A. capitellata. It was found that lipid content increased with decreasing growth rate for A. capitellata. Palmitic acid (C16:0) and palmitoleic acid (C16:1) were the principal fatty acids accounting for between 31%-33% and 31%-32% of total fatty acids, respectively. It is important to underline that red and blue light spectrum ranges contribute to improved biomass growth, whereas white light has the potential to support lipid content of diatoms. © 2019, Marine Technology Society Inc.. All rights reserved.Item Comparison of different photobioreactor configurations and empirical computational fluid dynamics simulation for fucoxanthin production(Elsevier B.V., 2019) Aslanbay Guler B.; Deniz I.; Demirel Z.; Oncel S.S.; Imamoglu E.Microalgae production in culture systems has been a topic of intense study for a long time. Optimization of cultivation conditions and design parameters of photobioreactors are essential for the development of economically and technically feasible algae technologies. The present study aimed to evaluate the effect of different photobioreactor (PBR) configurations on biomass and fucoxanthin production from Phaeodactylum tricornutum and to examine culture conditions by using Computational Fluid Dynamics (CFD) simulation for the photobioreactor having the maximum yield. The cells were first cultivated in three different PBRs (flat plate, airlift and stirred tank) and the maximum cell concentration of 5.94 ± 0.12 × 107 cells/ml was obtained in flat plate PBR. Also, highest fucoxanthin amount was found in the same PBR with the value of 2.43 ± 0.23 mg g−1. Flat plate PBR was simulated using CFD and the obtained results were used to evaluate mixing efficiency, flow dynamics and velocity fields. The extent of mixing was found sufficient to achieve homogenous culture medium and mean turbulent kinetic energy field suggested a homogeneous dissipation, also higher intensities of turbulence were observed around the nozzles and at the liquid-gas interphase. However, dead zones and vortex formations were observed in a small proportion of PBR. For further researches, assembling mixers or baffles into the PBR may be a feasible and effective method to improve the mixing efficiency and to prevent hydrodynamic problems. It was shown that the result of cultivation experiment had good agreement with that of CFD prediction. © 2018 Elsevier B.V.Item Transition from start-up to scale-up for fucoxanthin production in flat plate photobioreactor(Springer Netherlands, 2019) Aslanbay Guler B.; Deniz I.; Demirel Z.; Oncel S.S.; Imamoglu E.Fucoxanthin is one of the most important carotenoids and is found in diatoms such as Phaeodactylum tricornutum. The aim of this study was to evaluate the use of both the constant volumetric power consumption rate as scale-up strategy and the constant light energy per unit volume for transition from 1000-mL bottle to 2-L and 7-L flat plate photobioreactors for fucoxanthin production in P. tricornutum, considering whether an increase in the fucoxanthin yield could be achieved. The cell concentration and fucoxanthin content were enhanced with increasing the cultivation volume. It was found that the fucoxanthin yield increased 2.3 times in 2-L photobioreactor and 2.6 times in 7-L photobioreactor in comparison to the value of 1.05 mg g−1 dry weight in the cultivation bottle. Consequently, fucoxanthin production was successfully step-wise scaled-up from 1000-mL bottle to 7-L photobioreactor using both constant volumetric power consumption rate and the constant light energy per unit volume under laboratory conditions. © 2019, Springer Nature B.V.Item Computational fluid dynamics simulation in scaling-up of airlift photobioreactor for astaxanthin production(Elsevier B.V., 2020) Aslanbay Guler B.; Deniz I.; Demirel Z.; Imamoglu E.The unicellular green microalga Haematococcus pluvialis accumulates large amounts of the red ketocarotenoid astaxanthin. Aiming to cultivate these microalgae with high astaxanthin efficiency, cultivations were scaled-up from 1000 mL bottle to 2 L and 8 L airlift photobioreactor using volumetric power consumption rate (W/m3) as scale up strategy. After cultivations, computational fluid dynamics (CFD) simulation was used to investigate the flow patterns, mixing efficiency and gas holdup profile within the 2 L photobioreactor. At the end, astaxanthin content was enhanced with increasing the cultivation volume and highest astaxanthin amount of 49.39 ± 1.64 mg/g cell was obtained in 8 L photobioreactor. Hydrodynamic characteristics of photobioreactor was simulated and gas holdup showed difference between the riser and the downcomer regions. Velocity profiles of air and medium had higher values inside the draft tube than obtained in downcomer region. However liquid circulation was achieved from draft tube to the downcomer, mixing was not provided effectively considering the turbulence kinetic energy. For the further research, some developments about column configuration, sparger diameter may be necessary to enhance the mixing characteristics. © 2019 The Society for Biotechnology, JapanItem Evaluation of scale-up methodologies and computational fluid dynamics simulation for fucoxanthin production in airlift photobioareactor(John Wiley and Sons Ltd, 2020) Aslanbay Guler B.; Deniz I.; Demirel Z.; Imamoglu E.Researches about commercial-scale production of fucoxanthin are increasing day by day due to the much interest of its broad beneficial health effects. The aim of this study was to investigate the scale-up methodologies in airlift photobioreactor and to simulate fluid flow using computational fluid dynamics (CFD) for fucoxanthin production from Phaeodactylum tricornutum microalgae. During the transition process from 1-L cultivation bottle to the 2-L airlift photobioreactor, the constant mixing time, the constant volumetric oxygen transfer coefficient, and the constant volumetric power consumption rate were evaluated as scale-up methodologies under laboratory conditions. Maximum fucoxanthin yield was found as 1.01 ± 0.07 mg g−1 using scale-up strategy based on constant volumetric power consumption rate. After that, CFD simulation was performed in order to examine flow characteristics, mixing efficiency, hydrodynamics, and gas holdup for selected operation conditions. It was observed that mixing efficiency was low because the draft tube configuration prevented the circulation of fluid and caused a heterogenic culture medium inside the reactor. It is possible to overcome this bottleneck by developing the effective draft tube. © 2020 Curtin University and John Wiley & Sons, Ltd.Item Computational fluid dynamics modelling of stirred tank photobioreactor for Haematococcus pluvialis production: Hydrodynamics and mixing conditions(Elsevier B.V., 2020) Aslanbay Guler B.; Deniz I.; Demirel Z.; Oncel S.S.; Imamoglu E.Agitated photobioreactors (PBR) have been widespread for the cultivation of microalgae because of their advantages in mixing and mass transfer conditions. However, it is difficult to investigate the behaviors of cultivation broth flow with experimental procedures in these PBRs. Computational Fluid Dynamics (CFD) is a common method that has been used to simulate the performance of fluid containing systems in order to investigate the fluid flow, reduce the design cost and improve the efficiency. The objective of this study was to evaluate hydrodynamics and mixing conditions of stirred tank PBR for Haematococcus pluvialis production experimentally and numerically. The cells were first cultivated in a stirred tank PBR containing Rushton turbine impeller and the cell growth was examined during 10 days. At the end of cultivation, the cell concentration was reached the value of 3.1 ± 0.1 × 105 cells mL−1 with the total carotenoid content of 2.47 ± 0.01 mg L−1. Then, the hydrodynamic analyses were conducted to evaluate the average velocity magnitude, turbulence properties and dead zone inside the PBR. The simulation results obtained from realizable k-ε turbulence model showed that the uniformity index of average velocity was found as 0.86. This result showed that the fluid flow showed similar behavior in the most parts of PBR except around the impellers. The velocity contours supported that the mixing conditions were supplied efficiently, however the vortex formation was observed around the impellers in spite of the baffles. In addition, the turbulence kinetic energy having a vital influence on mixing characteristics was found between the values of 1.0 × 10−2 and 3.0 × 10−2 m2 s−2 and the lowest values were observed between two impellers due to extent of mixing. Obtained results could be used to re-design PBR configurations considering the impeller type, the distance between impellers and cultivation conditions. © 2020 Elsevier B.V.Item A novel subcritical fucoxanthin extraction with a biorefinery approach(Elsevier B.V., 2020) Aslanbay Guler B.; Deniz I.; Demirel Z.; Yesil-Celiktas O.; Imamoglu E.Eco-friendly, cost efficient and effective extraction methods have become significant for the industries applying zero waste principles. The two main objectives of this study were; to examine fucoxanthin extraction from wet Phaeodactylum tricornutum using subcritical fluid extraction and to characterize the residual biomass in order to determine the potential application areas. The highest fucoxanthin yield of 0.69 ± 0.05 mg/g wet cell weight was achieved using methanol with solvent-to-solid ratio of 200:1 at 120 rpm, 20 MPa pressure and at 35 °C for 60 min by subcritical extraction. Microscopy images showed that most of the cells were disrupted and intracellular components were effectively released. Based on the results of energy dispersive spectroscopy, biomass contained a mixture of organic molecules including mainly carbon (57–72%), oxygen (26–41%), magnesium (0.6–1.4%) and silica (0.4–1%) (wt%). These results make the residual biomass a potential candidate for various areas such as bioenergy, material sciences and sensor technologies. © 2019 Elsevier B.V.Item Long-term storage of microalgae: determination of optimum cryopreservation conditions(Cambridge University Press, 2022) Deniz I.; Demirel Z.; Imamoglu E.; Conk-Dalay M.Maintenance of eukaryotic microalgae strains for the long term is generally carried out using serial subculture techniques which require labour, time and cost. Cryopreservation techniques provide long-term storage of up to years for numerous microorganism strains and cell cultures. Ssu930ijn vbvbhnn8;l,n is related to a successfully designed mass and heat transfer balance throughout the cell. In this study, optimization of the cryopreservation process was carried out for two commercially used microalgal strains. The parameters to be optimized were DMSO percentage (0-25%), incubation time (1-15 min) and cryopreservation term (7-180 days) using a central composite design (CCD). Long-term storage up to 123.17 and 111.44 days corresponding to high cell viabilities was achieved for Chlorella vulgaris and Neochloris texensis, respectively. Generated models were found to be in good agreement with experimental results. The study also revealed holistic results for storage of microalgal strains in a stable state for industrial applications. Copyright © The Author(s), 2022. Published by Cambridge University Press on behalf of Marine Biological Association of the United Kingdom.Item Evaluation of different scale-up strategies for Haematococcus pluvialis cultivation in airlift photobioreactors(Istanbul University Faculty of Aquatic Sciences, 2022) Guler B.A.; Deniz I.; Demirel Z.; Imamoglu E.Large scale algal biomass production can be very challenging due to the potential issues of sustainability, environmental ethics, and economic concerns. A strategic approach to the transition from the laboratory to the industrial scale allows the prediction of process characteristics, design and analysis of large scale systems, and reduction of extra costs. In this study, a scale-up procedure that considered different approaches was carried out by selecting the Haematococcus pluvialis as a model organism. Three scale-up parameters (constant mixing time (tm), volumetric power consumption rate (P/V), and oxygen mass transfer coefficient (kLa)) were tested for biomass production in a 2-L airlift photobioreactor and they were compared with those obtained from a 1-L aerated cultivation bottle. Among three strategies, the maximum cell concentration, 4.60±0.20×105 cells/mL, was obtained in a constant volumetric power consumption rate experiment. Also, total carotenoid amount showed similar changes with the cell concentration and reached the maximum concentration of 2.02±0.11 mg/L under constant P/V experiment. However, the cultivation bottle presented the highest biomass amount of 0.62 g/L and specific growth rate of 0.38 day-1 of all of the photobioreactors. This result might be attributed to the low aeration rates or improper configuration of the system, which created a non-homogenous culture medium and led to ineffective mass transfer. © 2022 Revista Mexicana de Ciencias Forestales. All rights reserved.Item Aligned with sustainable development goals: microwave extraction of astaxanthin from wet algae and selective cytotoxic effect of the extract on lung cancer cells(Taylor and Francis Ltd., 2023) Aslanbay Guler B.; Saglam-Metiner P.; Deniz I.; Demirel Z.; Yesil-Celiktas O.; Imamoglu E.Astaxanthin is one of the most attractive carotenoid in the cosmetic, food, pharmaceutical, and aquaculture industries due to its strong bioactive properties. Among the various sources, several algae species are considered as rich sources of astaxanthin. Downstream processing of algae involves the majority of the total processing costs. Thus, elimination of high energy involved steps is imperative to achieve cost-effective scale in industry. This study aimed to determine operation conditions for astaxanthin extraction from wet Haematococcus pluvialis using microwave-assisted extraction. The isolated astaxanthin extract was evaluated for cytotoxicity on human lung cancer cells. The microwave-assisted extraction process at 75 °C under the power of 700 Watt for 7 min gave the highest astaxanthin yield (12.24 ± 0.54 mg astaxanthin/g wet cell weight). Based on MTT cell viability and Hoechst 33342 nuclear staining assays on A549 lung cancer cells, astaxanthin inhibited cell growth in dose- and time-dependent manners, where IC50 value was determined as 111.8 ± 14.8 µg/mL and apoptotic bodies were observed along with positive control group at 72 hr. These results showed that the treatment with astaxanthin extracted from wet H. pluvialis by microwave-assisted extraction exhibited anti-cancer activity on lung cancer cells indicating a newly potential to be utilized in industry. © 2022 Taylor & Francis Group, LLC.Item Design of chemobrionic and biochemobrionic scaffolds for bone tissue engineering(Nature Research, 2024) Aslanbay Guler B.; Morçimen Z.G.; Taşdemir Ş.; Demirel Z.; Turunç E.; Şendemir A.; Imamoglu E.Chemobrionic systems have attracted great attention in material science for development of novel biomimetic materials. This study aims to design a new bioactive material by integrating biosilica into chemobrionic structure, which will be called biochemobrionic, and to comparatively investigate the use of both chemobrionic and biochemobrionic materials as bone scaffolds. Biosilica, isolated from Amphora sp. diatom, was integrated into chemobrionic structure, and a comprehensive set of analysis was conducted to evaluate their morphological, chemical, mechanical, thermal, and biodegradation properties. Then, the effects of both scaffolds on cell biocompatibility and osteogenic differentiation capacity were assessed. Cells attached to the scaffolds, spread out, and covered the entire surface, indicating the absence of cytotoxicity. Biochemobrionic scaffold exhibited a higher level of mineralization and bone formation than the chemobrionic structure due to the osteogenic activity of biosilica. These results present a comprehensive and pioneering understanding of the potential of (bio)chemobrionics for bone regeneration. © The Author(s) 2024.Item Photobioreactor facade panels: enhancing comfort, reducing energy use, and capturing carbon in temperate continental climates(Springer Nature, 2025) Yaman Y.; Tokuç A.; Deniz İ.; Ezan M.A.; Köktürk G.; Dalay M.C.; Demirel Z.Buildings contribute around 37% to global carbon emissions, prompting a growing interest in innovative carbon capture technologies. Among these, the integration of microalgae-based photosynthesis into building facades has emerged as a promising solution. This approach offers multiple benefits, including carbon sequestration, reduced energy consumption, dynamic shading, and improved thermal regulation. This paper investigates the impact of integrating photobioreactor (PBR) facade elements, specifically on the south-facing facade of an office building in a temperate continental climate. The study evaluates the system’s effects on indoor thermal and visual comfort, energy production, and carbon dioxide (CO2) sequestration for three distinct PBR facade alternatives and compares them with a commercial curtain wall. The continuous PBR system varies in performance depending on production intensity, necessitating an initial optimization for thermal and visual comfort alongside energy use. Simulations were conducted using Rhinoceros/Grasshopper plug-ins, with optimization performed via the Octopus tool. The results, focusing on the Chlorella vulgaris algae strain, demonstrate that all facade configurations achieve a daylight performance exceeding 50% and meet desired thermal comfort levels. Although the energy generated by the PBR facade does not fully offset the building’s energy consumption, annual CO2 sequestration ranges from 84.87 kg to 770.13 kg. This study concludes that microalgae facades offer a viable strategy for enhancing a building’s energy performance and reducing CO2 emissions, without compromising occupant comfort. Additionally, the findings provide valuable insights for designers, researchers, investors and stakeholders and provides a payback period of these systems (16–24 years) for commercialization in the building industry. © Jiangnan University 2024.