Browsing by Author "Dizge, Nadir"

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Immobilization of Candida Antarctica a and Thermomyces Lanuginosus Lipases on Cotton Terry Cloth Fibrils Using Polyethyleneimine
(Elsevier, 2012) Ondul, Eda; Dizge, Nadir; Albayrak, Nedim
In this study, cotton terry cloth fibrils were coated with 0.2% polyethyleneimine (PEI). Lipases from Candida antarctica A (CALA) and Thermomyces lanuginosus (TL) were immobilized on this support through adsorption followed by cross-linking with 0.2% glutaraldehyde. PEI-enzyme aggregates formation and growth of aggregates on cotton cloth fibrils lead to multilayer immobilization of the lipases. PEI and lipase was mixed to form PEI-enzyme complex/aggregate. The highest amount of enzyme precipitate was obtained at the PEI to enzyme ratio of 1/20-1/40 for both lipases. The effect of pH was also investigated for aggregates formation. The results showed that when pH values were below 8, aggregation and precipitation were not occurred for C. antarctica A lipase. However, pH did not affect PEI-enzyme aggregate formation for T. lanuginosus lipase. Immobilized enzyme amount was approximately 180 mg/g support and 200 mg/g support for T. lanuginosus and C. antarctica A lipases, respectively. Effect of the reaction temperature on the relative activity of the free and immobilized lipases at various temperature (30-80 degrees C) was studied. It was found that immobilization had no effect on the optimum temperature and it was 60 degrees C for both free and immobilized enzymes. The effect of operational and storage stability on activity of free and immobilized lipases were also investigated. Immobilized lipases exhibited that they could be stored at room temperature with a little activity lost during 28 days. (C) 2012 Elsevier B.V. All rights reserved.
Investigation of Antibacterial Activity and Polyethersulfone (Pes) Membrane Usability of Delafossite-Type Cumno2 and Cumno2-Nh2 Nanostructures
(Springer, 2025) Yildirim, Rahel; Ozdemir, Sadin; Tollu, Gulsah; Gulcan, Mehmet; Filiz, Volkan; Dizge, Nadir
Membrane fouling is one of the most important issues in membrane studies and remains a current challenge. Therefore, developing composite membranes to reduce fouling is essential. In this study, delafossite-type CuMnO2 and CuMnO2-NH2 nanostructures were synthesized and characterized in detail using various instrumental tools, including SEM, SEM-Elemental Mapping, P-XRD, BET, and FTIR. The biological properties of CuMnO2 and CuMnO2-NH2 nanostructures, including antioxidant, antimicrobial, cell viability, antidiabetic activity, antibiofilm activity, and DNA fragmentation, were examined. Both materials exhibited good antioxidant, antimicrobial, and antibiofilm properties. The highest antioxidant activity for CuMnO2 was 75.93% at 100 mg/L, while the highest antioxidant activity for CuMnO2-NH2 was 92.35% at 100 mg/L. The most effective MIC value of 16 mg/L was obtained for CuMnO2 against Enterococcus hirae and Enterococcus faecalis. The highest amylase activity, at 165.2%, was observed at 100 mg/L for CuMnO2. Both CuMnO2 and CuMnO2-NH2 exhibited complete inhibition of microbial cell viability (100%) at 100 mg/L. Additionally, they demonstrated excellent biofilm inhibition activities against S. aureus and P. aureginosa. Furthermore, the use of polyethersulfone (PES) membranes coated with CuMnO2 and CuMnO2-NH2 compounds for the eradication of Escherichia coli was investigated, along with the antibacterial activities of the membrane surface and permeate.