Adil Denizli

BIOSORPTION OF CADMIUM(II), LEAD(II) AND COPPER(II) WITH THE FILAMENTOUS FUNGUS PHANEROCHAETE CHRYSOSPORIUM

The biosorption from artificial wastewaters of heavy metals (Cd(II), Pb(II) and Cu(II)) onto the dry fungal biomass of Phanerochaete chryosporium was studied in the concentration range of 5-500 mg l(-1). The maximum absorption of different heavy metal ions on the fungal biomass was obtained at pH 6.0 and the biosorption equilibrium was established after about 6 h. The experimental biosorption data for Cd(II), Pb(II) and Cu(II) ions were in good agreement with those calculated by the Langmuir model.

Dye-ligand affinity systems.

Dye-ligands have been considered as one of the important alternatives to natural counterparts for specific affinity chromatography. Dye-ligands are able to bind most types of proteins, in some cases in a remarkably specific manner. They are commercially available, inexpensive, and can easily be immobilized, especially on matrices bearing hydroxyl groups. Although dyes are all synthetic in nature, they are still classified as affinity ligands because they interact with the active sites of many proteins mimicking the structure of the substrates, cofactors, or binding agents for those proteins. A number of textile dyes, known as reactive dyes, have been used for protein purification. Most of these reactive dyes consist of a chromophore (either azo dyes, anthraquinone, or phathalocyanine), linked to a reactive group (often a mono- or dichlorotriazine ring). The interaction between the dye ligand and proteins can be by complex combination of electrostatic, hydrophobic, hydrogen bonding. Selection of the supporting matrix is the first important consideration in dye-affinity systems. There are several methods for immobilization of dye molecules onto the support matrix, in which usually several intermediate steps are followed. Both the adsorption and elution steps should carefully be optimized/designed for a successful separation. Dye-affinity systems in the form of spherical sorbents or as affinity membranes have been used in protein separation.

Batch removal of copper(II) and zinc(II) from aqueous solutions with low-rank Turkish coals

Abstract The removal of heavy-metal ions from aqueous solutions containing low-to-moderate levels of contamination using Turkish Beypazari low-rank coal was investigated. Carboxylic acid and phenolic hydroxyl functional groups present on the coal surface were the adsorption site to remove metal ions from solution via ion exchange. The equilibrium pH of the coal/solution mixture has been shown to be the principal factor controlling the extent of removal of Cu(II) and Zn(II) ions from aqueous solutions. The optimum pH was measured to be 4.0 and it was found that the adsorption reached equilibrium in 20 min. The maximum adsorption capacities of the metal ions from their single solutions were 1.62 mg for Cu(II) and 1.20 mg for Zn(II) per g of coal. The order of affinity based on a weight uptake by coal was as follows: Cu(II)>Zn(II). The same behavior was observed during the competitive adsorption, that is in the case of adsorption from their binary solutions. The adsorption phenomena appeared to follow a typical Langmuir isotherm. It was observed that use of low-rank coal was considerably effective in removing Cu(II) and Zn(II) ions from aqueous solutions. Higher amounts of adsorbed metal ions could be desorbed (up to 80%) using 25 mM EDTA. Low-rank Turkish coals are suitable for consecutive use for more than three cycles without significant loss of adsorption capacity.

Entrapment of Lentinus sajor-caju into Ca-alginate gel beads for removal of Cd(II) ions from aqueous solution: preparation and biosorption kinetics analysis

Abstract A white rot fungus species Lentinus sajor-caju biomass was entrapped into alginate gel via a liquid curing method in the presence of Ca(II) ions. The biosorption of cadmium(II) by the entrapped live and dead fungal biomass has been studied in a batch system. The heat-treatment process enhanced the biosorption capacity of the immobilized fungal biomass. The effect of initial cadmium concentration, pH and temperature on cadmium removal has been investigated. The maximum experimental biosorption capacities for entrapped live and dead fungal mycelia of L. sajur-caju were found to be 104.8±2.7 mg Cd(II) g −1 and 123.5±4.3 mg Cd(II) g −1 , respectively. The kinetics of cadmium biosorption was fast, approximately 85% of biosorption taking place within 30 min. The biosorption equilibrium was well described by Langmuir and Freundlich adsorption isotherms. The change in the biosorption capacity with time is found to fit pseudo-second-order equations. Cadmium binding properties of entrapped fungal preparations have been determined applying the Ruzic equations. Since the biosorption capacities are relatively high for both entrapped live and dead forms, they could be considered as suitable biosorbents for the removal of cadmium in wastewater treatment systems. The biosorbents were reused in three consecutive adsorption/desorption cycles without significant loss in the biosorption capacity.

Hydrolysis of sucrose by invertase immobilized onto novel magnetic polyvinylalcohol microspheres

Abstract The magnetic polyvinylalcohol (PVAL) microspheres were prepared by crosslinking glutaraldehyde. 1,1′-Carbonyldiimidazole (CDI), a carbonylating agent was used for the activation of hydroxyl groups of polyvinylalcohol, and invertase immobilized onto the magnetic PVAL microspheres by covalent bonding through the amino group. The retained activity of the immobilized invertase was 74%. Kinetic parameters were determined for immobilized invertase, as well as for the free enzyme. The K m values for immobilized invertase (55 mM sucrose) were higher than that of the free enzyme (24 mM sucrose), whereas V max values were smaller for the immobilized invertase. The optimum operational temperature was 5°C higher for immobilized enzyme than that of the free enzyme. The operational inactivation rate constant ( k opi ) of the immobilized invertase at 35°C with 200 mM sucrose was 5.83×10 −5 min −1 . Thermal and storage stabilities were found to increase with immobilization.

Lysine-Promoted Colorimetric Response of Gold Nanoparticles: A Simple Assay for Ultrasensitive Mercury(II) Detection

Although numerous methods have been reported for the analysis of toxic mercury (Hg(2+)) ions in drinking water, development of simple, rapid, inexpensive, and sensitive sensors still remains a great challenge. Here, we report a simple yet very sensitive colorimetric assay for rapid detection of Hg(2+) in water. The colorimetric assay is based on the aggregation of as-prepared citrate-capped gold nanoparticles (AuNPs) in the presence of Hg(2+) ions and the positively charged amino acid, lysine. The detection limit of this inexpensive colorimetric assay is 2.9 nM, which is below the limit value (10 nM) defined by the U.S. Environmental Protection Agency in drinkable water. Also, the colorimetric response of citrate-capped AuNPs in the presence of lysine is very selective to the Hg(2+). In addition, the colorimetric assay is very fast, and all analyses can be completed within a few minutes.

Biosorption of Cadmium, Lead, Mercury, and Arsenic Ions by the Fungus Penicillium purpurogenum

The potential use of the fungus Penicillium purpurogenum to remove cadmium, lead, mercury, and arsenic ions from aqueous solutions was evaluated. Biosorption of heavy metal ions reached equilibrium in 4 h. Heavy metal ions binding by Penicillium purpurogenum was clearly pH dependent. Heavy metal loading capacity increased with increasing pH under acidic conditions, presumably as a function of heavy metal speciation and due to the H+ competition at the same binding sites. The adsorption of heavy metal ions reached a plateau value at around pH 5.0. The maximum adsorption capacities of heavy metal ions onto the fungal biomass under noncompetitive conditions were 35.6 mg/g for As(III), 70.4 mg/g for Hg(II), 110.4 mg/g for Cd(II) and 252.8 mg/g for Pb(II). Their adsorption behavior can be described at least approximately with the Langmuir equation. The competitive adsorption capacities of the heavy metal ions were 3.4 mg/g for As(III), 15.8 mg/g for Hg(II), 13.1 mg/g for Cd(II), and 41.8 mg/g for Pb(II) at 50 mmol/L initial concentration of metal ions. The same affinity order on a molar basis was observed under noncompetitive and competitive adsorption conditions, which was as follows: Pb(II)>Cd(II)>Hg(II)>As(III). The equilibrium loading capacity of Pb(II) was greater than that of other metal ions. This fungal biomass showed a preference for binding Pb(II) over Cd(II), Hg(II), and As(III). Elution of heavy metal ions was performed using 0.5 M HCl. The fungus Penicillium purpurogenum could be used for ten cycles for biosorption.

Quartz crystal microbalance based nanosensor for lysozyme detection with lysozyme imprinted nanoparticles

The aim of this study is to prepare quartz crystal microbalance (QCM) nanosensor for the real-time detection of lysozyme. In the first part, the lysozyme imprinted (MIP) nanoparticles were prepared by mini-emulsion polymerization. The MIP nanoparticles were characterized by TEM, zeta-sizer and FTIR-ATR measurements. Particle size was found around 50 nm. The MIP nanoparticles were attached by dropping of nanoparticle solution to gold surface and then, dried at 37°C for 6h. QCM nanosensor was characterized with AFM and ellipsometer. The observations indicated that the nanoparticle film was almost monolayer. The detection limit was found as 1.2 ng/mL. The specificity of the QCM nanosensor was shown by using albumin as a competitor molecule. The results show that the QCM nanosensor has high selectivity and sensitivity with a wide range of lysozyme concentrations in both aqueous solutions (0.2-1500 μg/mL) and natural sources (egg white) (460-1500 ng/mL).

Dye-ligand and metal chelate poly(2-hydroxyethylmethacrylate) membranes for affinity separation of proteins.

Cibacron Blue F3GA was covalently immobilized onto poly(2-hydroxyethyl methacrylate) pHEMA) membranes via the nucleophilic reaction between the chloride of its triazine ring and the hydroxyl group of pHEMA. Then, Fe3+ ions were complexed by chelation with the immobilized Cibacron Blue F3GA molecules. Different amounts of Fe3+ ions were loaded on the membranes by changing the concentration of Fe3+ ions and pH of the reaction medium. Membranes with or without Fe3+ were used in the adsorption of glucose oxidase, catalase and bovine serum albumin. The adsorption capacities of these membranes were determined by changing pH and the concentration of the proteins in the adsorption medium. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The maximum capacities (qm) of the Fe3+ complexed membranes for glucose oxidase, catalase and bovine serum albumin (8.70 x 10(-3) mumol m-2, 2.15 x 10(-3) mumol m-2 and 2.21 x 10(-3) mumol m-2) were greater than those of the untreated membranes (6.79 x 10(-3) mumol m-2, 1.34 x 10(-3) mumol m-2 and 1.94 x 10(-3) mumol m-2) respectively. The nonspecific adsorption of the enzymes and the protein on the pHEMA membranes was negligible.

Cibacron Blue F3G-A-attached monosize poly(vinyl alcohol)-coated polystyrene microspheres for specific albumin adsorption

Abstract Monosize polystyrene (PS) microbeads (4 μm in diameter) were produced by phase inversion polymerization of styrene in ethanol-methoxyethanol medium. They were coated with poly(vinyl alcohol) (PVAL) by adsorption and chemical cross-linking to decrease the non-specific protein adsorption. Cibacron Blue F3G-A was then attached for specific protein adsorption. The adsorption conditions were optimized to increase the amount of PVAL by changing the initial concentration of PVAL, and using different types of salts at different ionic strengths. Higher amounts of PVAL (up to 19 mg PVAL/g PS) were loaded by increasing the PVAL initial concentration and by using NA 2 SO 4 at a higher ionic strength (0.2). Bovine serum albumin (BSA) adsorption and desorption on these PS-based microbeads were also investigated under different conditions. PVAL coating prevented the non-specific BSA adsorption. A higher amount of BSA (up to 60 mg BSA/g dye-attached PS/PVAL) was specifically adsorbed on dye-attached PS microbeads, especially around pH 5 and lower ionic strengths (0.01). About 90% of the adsorbed BSA was desorbed in 1 h by using 0.5 M NaSCN.