GCRIS

Now showing 1 - 2 of 2

Preparation, Characterization of Enzyme Immobilized Membranes and Modeling Og Their Performances
(Izmir Institute of Technology, 2010) Yürekli, Yılmaz; Alsoy Altınkaya, Sacide
The objective of this thesis study is to prepare active and stable urease (URE) immobilized membranes for the efficient removal of urea and to predict the performances of these membranes under pressure. Two commercially available ultrafiltration membranes namely Poly (acrylonitrile-co-sodium methallyl sulfonate) copolymer (AN69) and polyethyleneimine (PEI) deposited AN69 membranes (AN69-PEI) were used as supporting materials on which urease is immobilized by means of physical adsorption using layer-by-layer self assembly method or chemical attachment using N-ethyl-N.-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and Nhydroxysuccinimide (NHS) coupling agents as a zero crosslinker. During physical immobilization (pH 7.4), the effect of polyelectrolyte type on the activity of immobilized urease was compared between PEI and chitosan (CHI) cationic polyelectrolytes where urease was located either on top of the polyelectrolyte layer (AN69-PEI-URE or AN69-CHI-URE) or between two polyelectrolyte layers in a sandwiched form (AN69-PEI-URE-PEI or AN69-CHI-URE-CHI). The results reveal that the amount of urease immobilized on AN69 membranes are similar and slightly higher than the amount adsorbed on the activated AN69 surface by chemical attachment (AN69-C-URE). The maximum reaction rate was observed with AN69-PEI-URE membrane while the maximum retained activity during storage time was determined with AN69-C-URE membrane. Under dynamic conditions, the hydraulic permeabilities of the commercial and urease immobilized membranes were found similar and the highest urea conversion was achieved with the AN69-PEI-URE-PEI membrane. At the end of 450 minutes of filtration under pressure, the catalytic activity of AN69-C-URE membrane was completely preserved. The mathematical model developed can correlate the experimental filtration data quite well.
Preparation of Tyrosinase Immobilized Chitosan and Gelatin Films for Detection of Parathion-Methyl
(Izmir Institute of Technology, 2012) Polatoğlu, İlker; Çakıcıoğlu Özkan, Seher Fehime
In this work, tyrosinase immobilized chitosan and gelatin films as optical enzyme sensors which were characterized and optimized by UV spectrophotometer, were developed for detection of the pesticide parathion-methyl. The results show that the best sensor was the chitosan supported ones (TCA) prepared by adsorption method due to higher responsiveness and higher catalytic activity. The prepared sensors used for 10 times without significant loss in activity indicate good operational stability. Immobilization of the enzyme to chitosan support increases the pH, temperature and storage stability with respect to free enzyme due to providing structural rigidity and appropriate flexibility by immobilization. The other indication is that, isopropyl alcohol is the most appropriate organic solvent to solve the pesticide due to showing higher solubility for parathion-methyl and lowest inhibition (decrease in activity) for the enzyme. TCA has wide linear detection range and it can detect the parathion methyl concentration below the Maximum Residue Limit (MRL). The decrease in enzyme activity was obtained up to 10 mg/l (ppm) parathion-methyl concentration. The other result is that, kinetics of the immobilized enzyme was reaction controlled for higher substrate concentrations as understood from effectiveness factor, η. Atomic force microscopy (AFM) and FTIR analysis show that tyrosinase enzyme was successfully coated on the surface of chitosan and gelatin films. After using the optical enzyme sensor the binding of product o-quinone to chitosan and gelatin films were observed which was characterized by AFM results and the UV visible absorption peaks.

Phd Degree / Doktora

Browse

Filters

Settings

Sort By

Results per page

Search Results