Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 15Citation - Scopus: 19Immobilization of Esterase From Bacillus Subtilis on Halloysite Nanotubes and Applications on Dibutyl Phthalate Degradation(Elsevier, 2023) Rosales, Emilio; Pazos, Marta; Sanroman, Maria Angeles; Balcı, Esin; Sofuoğlu, AysunDibutyl phthalate (DBP) is one of the listed phthalic acid esters (PAEs) known as the priority toxicants which exhibit carcinogenic and teratogenic properties and is responsible for endocrine disruption. Therefore, its removal has become a matter to tackle with. In this work, the feasibility of DBP degradation by esterase and lipase enzymes obtained from various microorganisms and the immobilization of the most effective in a clayey material were investigated. Esterase from Bacillus subtilis exhibited the highest degradation efficiency reaching a complete degradation. Its immobilization onto halloysite nanotubes (HNTs) by adsorption method was studied by response surface methodology using a central composite design face-centered. The four selected factors that affect the HNT-enzyme composite generation were: pH, adsorption time, enzyme/HNT (E/H) ratio, and adsorption temperature, and the optimal conditions were determined (pH 7, time 360 min, E/H ratio 0.2, temperature 30oC). Consequently, the activity did not significantly decrease by immobilization, and the adsorption efficiency and relative activity were determined to be 73.15% and 82.7%, respectively. Besides, the immobilization enhanced thermal and storage stability. As for enzyme reusability, after 7 continuous cycles, the composite maintained almost 75% of its initial activity. Both the free enzyme (1 mg/mL) and the composite degraded 100 mg/L DBP with 100% efficiency and several byproducts were detected. Moreover, the composite could be reused for 7 cycles keeping a remarkable catalytic activity. Overall, this study indicated that the HNT-enzyme composite may be used as an effective candidate for remediation of the environmental media contaminated with DBP and other PAEs.(c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Article Citation - WoS: 43Citation - Scopus: 42Immobilization of Superoxide Dismutase/Catalase Onto Polysulfone Membranes To Suppress Hemodialysis-Induced Oxidative Stress: a Comparison of Two Immobilization Methods(Elsevier Ltd., 2015) Yaşar Mahlıçlı, Filiz; Şen, Yasin; Mutlu, Mehmet; Alsoy Altınkaya, SacideThe objective of this study is to improve the blood compatibility of polysulfone (PSF) based hemodialysis membranes through generating antioxidative surfaces with superoxide dismutase (SOD)/catalase (CAT) enzyme couple immobilization. Enzymes were attached both covalently and ionically on the plasma treated and polyethyleneimine (PEI) deposited membranes, respectively. The loss of enzymes from PEI modified surface at the end of 4 h was found to be relatively higher during storage in phosphate buffered saline (PBS) at pH 7.4 when compared to the enzymes on the plasma treated surface. The kinetic studies indicated that SOD catalyzed the reaction in the diffusion-limited regime at all substrate concentrations and its inactivation by hydrogen peroxide was prevented in the presence of CAT. SOD/CAT coated PSF membranes were capable of reducing the levels of reactive oxygen species in blood and can significantly prolong activated partial thromboplastin time. In addition, both the adsorption of human plasma proteins and platelet activation on all modified membranes decreased significantly compared to the unmodified PSF membranes. Proposed modification methods did not affect high permeability, high mechanical strength or the non-toxic properties of the PSF membranes.Article Citation - WoS: 46Citation - Scopus: 52Effect of Enzyme Location on Activity and Stability of Trypsin and Urease Immobilized on Porous Membranes by Using Layer-By Self-Assembly of Polyelectrolyte(Elsevier Ltd., 2010) Guedidi, Sadika; Yürekli, Yılmaz; Deratani, André; Déjardin, Philippe; Innocent, Christophe; Alsoy Altınkaya, Sacide; Roudesli, Sadok; Yemenicioğlu, AhmetThe layer-by-layer (LbL) self-assembly of polyelectrolyte is one of the simplest ways to immobilize enzyme on membrane. In this paper, the immobilization of trypsin (TRY) and urease (URE) on polyacrylonitrile based membranes using the LbL assembly technique was presented. The studied systems consisted in bilayered assemblies with the enzyme layer as the outer layer and trilayered assemblies with the enzyme layer as the inner sandwiched layer. The membrane pore size was chosen so that the smaller enzyme TRY was mainly immobilized within the membrane and confined in the porous membrane structure while URE immobilization mainly took place at the membrane surface. No dramatic difference on reactivity was evidenced between these two enzyme locations. The catalytic activity of immobilized enzymes was found to be lower than the free ones in solution but their stability was dramatically enhanced. The higher activity was observed when the enzyme is deposited as the outer layer of the LbL assembly. On the other hand, the more stable catalytic membranes were obtained when the outer layer consists of a polyelectrolyte covering the enzyme layer. © 2010 Elsevier B.V.