Browsing by Author "Aslanbay Guler B."
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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 Biological conversion technologies: Enzyme hydrolysis, ethanol fermentation(Elsevier, 2023) Aslanbay Guler B.; Deniz I.; Ozmihci S.; Imamoglu E.In the context of increasing population, climate changes, and the depletion of energy resources, researchers have focused on the development of alternative renewable biofuels. Bioethanol has been identified as a biodegradable and environmentally friendly biofuel that gains much more interest as a future energy source. It is produced from various renewable resources including, starch, sugar, lignocellulosic materials, algal feedstocks, and agricultural/food processing waste by the fermentation process that contains four main sections including pretreatment, hydrolysis, fermentation, and downstream. Industrial fermentation processes are considered as an important biotechnological platform and there have been significant developments in order to improve conversion efficiency and reduce the capital and operation costs. This chapter focuses on the discussion of synergic studies from feedstock to life cycle assessment of bioethanol production as reported in the literature. © 2023 Elsevier Ltd. 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 Marine cosmetics and the blue bioeconomy: From sourcing to success stories(Elsevier Inc., 2024) Rotter A.; Varamogianni-Mamatsi D.; Zvonar Pobirk A.; Gosenca Matjaž M.; Cueto M.; Díaz-Marrero A.R.; Jónsdóttir R.; Sveinsdóttir K.; Catalá T.S.; Romano G.; Aslanbay Guler B.; Atak E.; Berden Zrimec M.; Bosch D.; Deniz I.; Gaudêncio S.P.; Grigalionyte-Bembič E.; Klun K.; Zidar L.; Coll Rius A.; Baebler; Lukić Bilela L.; Rinkevich B.; Mandalakis M.As the global population continues to grow, so does the demand for longer, healthier lives and environmentally responsible choices. Consumers are increasingly drawn to naturally sourced products with proven health and wellbeing benefits. The marine environment presents a promising yet underexplored resource for the cosmetics industry, offering bioactive compounds with the potential for safe and biocompatible ingredients. This manuscript provides a comprehensive overview of the potential of marine organisms for cosmetics production, highlighting marine-derived compounds and their applications in skin/hair/oral-care products, cosmeceuticals and more. It also lays down critical safety considerations and addresses the methodologies for sourcing marine compounds, including harvesting, the biorefinery concept, use of systems biology for enhanced product development, and the relevant regulatory landscape. The review is enriched by three case studies: design of macroalgal skincare products in Iceland, establishment of a microalgal cosmetics spin-off in Italy, and the utilization of marine proteins for cosmeceutical applications. © 2024 The Author(s)