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    Covalent Immobilization of Candida rugosa Lipase on Epichlorohydrin-Coated Magnetite Nanoparticles: Enantioselective Hydrolysis Studies of Some Racemic Esters and HPLC Analysis
    (Springer, 2020) Cakmak, Resit; Topal, Giray; Cinar, Ercan
    In this study, a new biocatalyst was prepared by immobilizing Candida rugosa lipase epichlorohydrin-functionalized onto the surface of the nanoparticles. Magnetite nanoparticles were obtained by chemical co-precipitation method of Fe2+ and Fe3+, and then the prepared uncoated and coated nanoparticles were characterized by XRD, FT-IR and TGA. Lipase was covalently attached to activated nanoparticles. The catalytic properties of free and immobilized lipases were determined. It was found that the optimum temperature for free and immobilized lipases was 30 degrees C and 35 degrees C, respectively. The optimum pH values were found to be 7.0 and 8 for free and immobilized lipases, respectively. Immobilized lipase was found to retain significant activity even after the seventh use. In the final section of the study, optically pure compounds were obtained by carrying out the enantioselective hydrolysis studies of racemic esters by using immobilized lipase. Enantiomeric excesses of the products in the enantioselective hydrolysis of racemic ibuprofen and naproxen methyl ester and racemic butyl mandelate were determined to be 94.93, 77.30 and 68.15, respectively.
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    Öğe
    Equilibrium and thermodynamic studies on biosorption of Pb(II) onto Candida albicans biomass
    (Elsevier Science Bv, 2009) Baysal, Zuebeyde; Cinar, Ercan; Bulut, Yasemin; Alkan, Hueseyin; Dogru, Mehmet
    Biosorption of Pb(II) ions from aqueous solutions was studied in a batch system by using Candida albicans. The optimum conditions of biosorption were determined by investigating the initial metal ion concentration, contact time, temperature, biosorbent dose and pH. The extent of metal ion removed increased with increasing contact time, initial metal ion concentration and temperature. Biosorption equilibrium time was observed in 30 min. The Freundlich and Langmuir adsorption models were used for the mathematical description of biosorption equilibrium and isotherm constants were also evaluated. The maximum biosorption capacity of Pb(II) on C. albicans was determined as 828.50 +/- 1.05, 831.26 +/- 1.30 and 833.33 +/- 1.12 mg g(-1), respectively, at different temperatures (25, 35 and 45 degrees C). Biosorption showed pseudo second-order rate kinetics at different initial concentration of Pb(II) and different temperatures. The activation energy of the biosorption (E-a) was estimated as 59.04 kJ mol(-1) from Arrhenius equation. Using the equilibrium constant value obtained at different temperatures, the thermodynamic properties of the biosorption (Delta G degrees, Delta H degrees and Delta S degrees) were also determined. The results showed that biosorption of Pb(II) ions on C. albicans were endothermic and spontaneous. The optimum initial pH for Pb(II) was determined as pH 5.0. FTIR spectral analysis of Pb(II) adsorbed and unadsorbed C. albicans biomass was also discussed. (C) 2008 Elsevier B.V. All rights reserved.
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    Öğe
    Identification and quantification of phenolic and volatile constituents in five different Anatolian thyme species using LC-MS/MS and GC-MS, with biological activities
    (Elsevier, 2021) Boga, Mehmet; Ozkan, Esra Eroglu; Ersoy, Ezgi; Tuncay, Eyyup; Canturk, Yeter Yesil; Cinar, Ercan; Kara, Emel Mataraci
    Being widely used in the food industry, thyme is one of the most valuable plants in many aspects, and Turkey is one of the hotspots for thyme industry. Five thyme species, Thymus convolutus (endemic), Thymus fallax, Thymus haussknechtii Velen (endemic), Thymus kotschyanus var. kotschyanus, and Thymus sipyleus from Turkey were subjected in this study. Their essential oils and the extracts of aerial and root parts were obtained. GC-MS analyses showed that camphor was the major compound in T. convolutus (12.7%), and in T. sipyleus (13.1%) essential oils. The major volatile compound of T. fallax was bicyclogermacrene (21.5%), whereas the T. kotschyanus var. kotschyanus essential oil showed a predominance of carvacrol (48.5%), and thymol (22.5%). Carvacrol was also the major compound of T. haussknechtii with 28.2%. LC-MS/MS analyses showed that nicotiflorin (293.28-4201.15 mu g/mL), caffeic (516.41-851.28 mu g/mL), quinic (344.37-4410.94 mu g/mL), rosmarinic (1800.18-9631.71 mu g/mL), and fumaric acid (350.88-682.10 mu g/mL) were detected as the main compounds in the extracts. All extracts exerted strong antioxidant activity, and the highest radical scavenging activity was demonstrated by T. haussknechtii root extract. T. convolutus and T. haussknechtii aerial parts extracts showed significant antimicrobial activity against C. tropicalis at MIC of 19.53 mu g/mL. The extracts were found to be nontoxic against COLO205 and KM12 human colon, and UO-31, and A498 human renal cell lines. Their enzyme inhibitory activities were also evaluated against cholinesterase, tyrosinase and urease enzymes and T. fallax aerial part extract was the most effective with 34.48 +/- 0.60% in antibutyrylcholinesterase activity. These species with strong antioxidant and antifungal properties and no toxicity could be beneficial to be used as preservatives in the food processing industry.