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Öğe Biosorption of chromium(VI) ions from aqueous solution by the bacterium Bacillus thuringiensis(2005) Şahin Y.; Öztürk A.The biosorption of chromium(VI) ions from aqueous solutions on dried vegetative cell and spore-crystal mixture of Bacillus thuringiensis var. thuringiensis was tested using the batch method as a function of pH, initial metal ion concentration and temperature. The optimum adsorption pH value observed for chromium(VI) ions was 2.0. At the optimal conditions, metal ion uptake has rised with increasing initial metal ion concentration. Chromium(VI) ions uptake of B. thuringiensis' spore-crystal mixture at 250 mg l-1 was 24.1%, whereas its vegetative cell metal uptake was 18.0%. Chromium(VI) biosorption experiments were carried out at three different temperatures, 15, 25 and 35°C. The best temperature for biosorption was 25°C. Scatchard plot analysis were used to obtain more compact information about the interaction between chromium(VI) ions and biosorbents. The plot results are further studied to determine if they fit Langmuir and Freundlich models. Scatchard analysis of the equilibrium binding data for chromium(VI) ions on vegetative cell and spore-crystal mixture of B. thuringiensis gave rise to a linear plot, indicating that the Langmuir model could be applied. The adsorption data with respect to the metal provided an excellent fit to both Langmuir and Freundlich isotherms. © 2004 Elsevier Ltd. All rights reserved.Öğe Removal of nickel from aqueous solution by the bacterium Bacillus thuringiensis(2007) Öztürk A.The biosorption of the toxic metal (nickel) from aqueous solutions on dried vegetative cell and spore-crystal mixture of Bacillus thuringiensis var. thuringiensis was tested under laboratory conditions as a function of pH, initial metal ion concentration and temperature. The characteristics of the adsorption process were investigated using Scatchard analysis. Scatchard analysis of the equilibrium binding data for metal ions on vegetative cell and spore-crystal mixture of B. thuringiensis gave rise to a linear plot, indicating that the Langmuir model could be applied successfully. Adsorption behaviour of nickel(II) ion on B. thuringiensis is expressed by both Langmuir and Freundlich isotherms. The adsorption data with respect to the metal provided an excellent fit to both isotherms. Ni(II) ion uptake of B. thuringiensis's spore-crystal mixture at 250 mg l-1 was 15.7%, whereas its vegetative cell metal uptake was 10%. The best temperature for ion uptake was found to be at 35 °C. © 2007 Elsevier B.V. All rights reserved.Öğe Response of some microalgae to herbicides(1997) Dönmez G.Ç.; Öztürk A.The growth response of Scenedesmus kissi Hortob. (Scenedesmaceae), S. obliquus (Turp) Kütz. (Scenedesmaceae), Chlorella vulgaris Beyerinck (Chlorellaceae) and Synechocystis sp. Sauvageau (Cyanophyceae) to various concentrations of four different herbicides (chlorsulfuron, tribenuron-methyl, dimethylamin, isooctylester) were studied in laboratory cultures. The four herbicides were chosen as the experimental materials because of their wide use in weed control in cereal fields in Turkey. All of the herbicides tested had effects on microalgal growth depending on the concentration in a BG 11 solid medium. Of the four herbicides examined, isooctylester was commonly used herbicide around Mogan Lake. All of the species isolated from this lake were found to be tolerant issoctylester.Öğe Toxicological effect of indole and its azo dye derivatives on some microorganisms under aerobic conditions(2006) Öztürk A.; Abdullah M.I.Azo dyes are ubiquitous commercial chemicals that present unique environmental problems. The azo dyes in particular can undergo natural anaerobic degradation to potentially carcinogenic amines. They pose a major problem for water-treatment plants downstream. One strategy to remidate polluted surface contaminants is to make use of the degradative capacity of bacteria rather than using destructive chemical reactions. Therefore, pathogenic and non-pathogenic microorganisms namely; Bacillus thuringiensis, Bacillus subtilis, Bacillus megaterium, Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Saccharomyces cerevisiae have been chosen and the toxicological effect of indole and its azo dye methyl derivatives on these microorganisms was studied under aerobic conditions. While these compounds have showed remarkable activity against B. megaterium, B. subtilis, B. thuringiensis and S. aureus, they did not exhibit any activity against P. vulgaris. However, indole acted as an inhibitor on all of these compounds specially the Gram negative bacterium P. aeruginosa. © 2005 Elsevier B.V. All rights reserved.
