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Adsorption of heavy metal ions onto ethylene diamine-derived and Cibacron Blue F3GA-incorporated microporous poly(2-hydroxyethyl methacrylate) membranes
(Elsevier Science Bv, 2000) Denizli, A; Say, R; Patir, S; Arica, MY
Microporous poly( 2-hydroxyethylmethacrylate) (PHEMA) membranes carrying ethylene diamine (EDA) and Cibacron Blue F3GA were prepared for the removal of heavy metal ions (i.e. mercury, copper, lead and cadmium) from aqueous solutions containing different amounts of these ions (5-700 mu g 1(-1)) and at different pH values (2.0-8.0). The non-specific adsorption of heavy metal ions on the underived membranes was very low (3.3 mmol/m(2) for Hg(II), 0.5 mmol/m(2) for Cu(II), 1.2 mmol/m(2) for Pb(II) and 1.1 mmol/m(2) for Cd(II)). Cibacron Blue F3GA attachment significantly increased the heavy metal adsorption (16.3 mmol/m(2) for Hg(II), 19.9 mmol/m(2) for Cu(II), 23.4 mmol/m(2) for Pb(II) and 38.4 mmol/m(2) for Cd(LI)). When the heavy metal ions competed (in the case of the adsorption from a mixture) the adsorption capacities were 7.1 mmol/m(2) for Hg(II), 17.9 mmol/m(2) for Cu(II), 6.2 mmol/m(2) for Pb(II) and 9.1 mmol/m(2) for Cd(lI). The observed order in adsorption was found to be Cd(II) > Pb(II) > Cu(II) > Hg(II) for non-competitive conditions. The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 5.0. Desorption of heavy metal ions was achieved using 0.1 M HNO3. These membranes are suitable for repeated use for more than five cycles without considerable loss of adsorption capacity. (C) 2000 Elsevier Science B.V. All rights reserved.
Affinity dye-ligand poly(hydroxyethyl methacrylate)/chitosan composite membrane for adsorption lysozyme and kinetic properties
(Elsevier Science Sa, 2003) Bayramoglu, G; Yilmaz, M; Arica, MY
A composite membrane from 2-hydroxyethyl methacrylate (HEMA) and poly(hydroxyethyl methacrylate)/chitosan (pHEMA/chitosan) was synthesized via UV initiated photo-polymerization in the presence of an initiator alpha,alpha'-azoisobutyronitrile (AIBN). Procion Brown MX 5BR was then covalently immobilized onto composite membrane as a dye-ligand. The binding characteristics of a model protein (i.e. lysozyme) to the dye-ligand immobilized affinity membrane have been investigated from aqueous solution using the plain composite membrane as a control system. The experimental data was analyzed using two adsorption kinetic models, the pseudo-first-order and the pseudo-second-order, to determine the best-fit equation for the adsorption of lysozyme onto affinity composite membrane. The second-order equation for the adsorption of lysozyme on the dye-ligand membrane systems is the most appropriate equation to predict the adsorption capacity for the affinity membrane. The reversible lysozyme adsorption on the affinity membrane obeyed the Freundlich isotherm. The lysozyme adsorption capacity of the plain membrane and the dye-ligand affinity membrane were 8.3 and 121.5 mg ml(-1), respectively. (C) 2002 Elsevier Science B.V. All rights reserved.
Affinity interaction of hydroxypyruvate reductase from Methylophilus spp. with Cibacron blue F3GA-derived poly(HEMA EGDMA) microspheres: partial purification and characterization
(Elsevier Sci Ltd, 1999) Arica, MY; Halicigil, C; Alaeddinoglu, G; Denizli, A
A methylotrophic hydroxypyruvate reductase was partially purified and characterized from Methylophilus spp. using the biomimetic dye, Cibacron Blue F3FA attached to poly(HEMA-EGDMA) microspheres. The absorption capacities of the dye-affinity microspheres were determined by changing pH and the concentration of the proteins in the adsorption medium. Hydroxypyruvate reductase was desorbed from the dye-affinity support specifically with 2 mM NADH solution. The enzyme was purified 10.4-fold with 47% yield. The molecular mass and subunit molecular mass of the enzyme was estimated to be 75 kDa and 37 kDa on the basis of its mobility in polyacrylamide and SDS-polyacrylamide gels, respectively. This suggested a homogeneous dimer structure. The optimal pH was between 5.0 and 7.0, and the maximum enzyme activity was obtained at 50 degrees C. The K-m values of hydroxpyruvate reductase were 0.222 mM for hydroxpyruvate and 0.067 mM for NADH. (C) 1999 Elsevier Science Ltd. All rights reserved.
Affinity membrane chromatography: relationship of dye-ligand type to surface polarity and their effect on lysozyme separation and purification
(Elsevier, 2004) Arica, MY; Yilmaz, M; Yalcin, E; Bayramoglu, G
Two different dye-ligands, i.e. Procion Brown MX-5BR (RB-10) and Procion Green H-4G (RG-5) were immobilised onto poly(2-hydroxyethylmethacrylate) (pHEMA) membranes. The polarities of the affinity membranes were determined by contact angle measurements. Separation and purification of lysozyme from solution and egg white were investigated. The adsorption data was analysed using two adsorption kinetic models the first order and the second order to determine the best-fit equation for the separation of lysozyme using affinity membranes. The second-order equation for the adsorption of lysozyme on the RB-10 and RG-5 immobilised membranes systems is the most appropriate equation to predict the adsorption capacity for the affinity membranes. The reversible lysozyme adsorption on the RB-10 and RG-5 did not follow the Langmuir model, but obeyed the Temkin and Freundlich isotherm model. Separation and purification were monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. The purities of the eluted lysozyme, as determined by HPLC, were 76 and 92% with recovery 63 and 77% for RB-10 and RG-5 membranes, respectively. For the separation and purification of lysozyme the RG-5 immobilised membrane provided the best results. The affinity membranes are stable when subjected to sanitization with sodium hydroxide after repeated adsorption-elution cycles. (C) 2004 Elsevier B.V. All rights reserved.
Affinity microspheres and their application to lysozyme adsorption: Cibacron Blue F3GA and Cu(II) with poly(HEMA-EGDMA)
(Wiley, 1999) Denizli, F; Denizli, A; Arica, MY
Lysozyme adsorption onto Cibacron Blue F3GA attached and Cu(II) incorporated poly(2-hydroxyethyl methacrylate-ethylene glycol dimethacrylate) [poly(HEMA-EGDMA)] microspheres was investigated. The microspheres were prepared by suspension polymerization. Various amounts of Cibacron Blue F3GA were attached covalently onto the microspheres by changing the initial concentration of dye in the reaction medium. The microspheres with a swelling ratio of 65%, and carrying different amounts of dye (between 1.4 and 22.5 mu mol/g(-1)) were used in the lysozyme adsorption studies. Lysozyme adsorption on these microspheres from aqueous solutions containing different amounts of lysozyme at different pH values was investigated in batch reactors. The lysozyme adsorption capacity of the dye-metal chelated microspheres (238.2 mg g(-1)) was greater than that of the dye-attached microspheres (175.1 mg g(-1)). The maximum lyzozyme adsorption capacities (q(m)) and the dissociation constant (k(d)) values were found to be 204.9 mg g(-1) and 0.0715 mg ml(-1) with dye-attached and 270.7 mg g(-1) and 0.0583 mg ml(-1) with dye-metal chelated microspheres, respectively. More than 90% of the adsorbed lysozyme were desorbed in 60 min in the desorption medium containing 0.5 M KSCN at pH 8.0 or 25 mM. EDTA at pH 4.9. (C) 1999 Society of Chemical Industry.
Biosorption of heavy metal ions on immobilized white-rot fungus Trametes versicolor
(Elsevier, 2003) Bayramoglu, G; Bektas, S; Arica, MY
Trametes versicolor mycelia were immobilized in carboxymethylcellulose, CMC, beads via entrapment, and the bead containing immobilized fungus spores were incubated at 30 degreesC for 3 days to attain uniform growth on the bead surface. After incubation, the live and heat inactivated immobilized fungus on the CMC beads were used for the biosorption of Cu2+, Pb2+ and Zn2+ ions. Plain CMC beads were used as a control system. The biosorption of Cu2+, Pb2+ and Zn2+ ions by the CMC and both live and inactivated immobilized preparations increased as the initial concentration of Cu2+, Pb2+ and Zn2+ ions in the medium increased. The maximum biosorption capacities for both immobilized live and heat inactivated Trametes versicolor were 1.51 and 1.84 mmol Cu2+, 0.85 and 1.11 mmol Pb2+ and 1.33 and 1.67 mmol Zn2+ per g of dry biosorbents, respectively. Biosorption equilibrium was established in about 1.0h and the equilibrium was well described by Langmuir and Freundlich isotherms. A temperature change in the range of 15-45 degreesC did not affect the biosorption capacity. The affect of pH was also investigated and the maximum adsorption of Cu2+, Pb2+ and Zn2+ ions on the CMC and both live and inactivated immobilized fungal biomass was observed between pH 4.0 and 6.0. The CMC beads with the immobilized fungus can be regenerated using 10 mM HCl, with up to 97% recovery of the metal ions; the biosorbents reused up to five biosorption-desorption cycles without any major loss in the biosorption capacity. (C) 2003 Elsevier B.V. All rights reserved.
Biosorption of Hg2+, Cd2+, and Zn2+ by Ca-alginate and immobilized wood-rotting fungus Funalia trogii
(Elsevier, 2004) Arica, MY; Bayramoglu, G; Yilmaz, M; Bektas, S; Genc, O
Funalia trogii biomass was immobilized in Ca-alginate gel beads. The live and beat inactivated immobilized forms were used for the biosorption of Hg2+, Cd2+ and Zn2+ ions by using plain Ca-alginate gel beads as a control system. The effect of pH was investigated and the maximum adsorption of metal ions on the Ca-alginate and both live and inactivated immobilized fungal preparations were observed at pH 6.0. The temperature change between 15 and 45 degreesC did not affect the biosorption capacity. The biosorption of Hg2+, Cd2+ and Zn2+ ions on the Ca-alginate beads and on both immobilized forms was studied in aqueous solutions in the concentration range of 30-600 mg/L. The metal biosorption capacities of the heat inactivated immobilized E trogii for Hg2+, Cd2+ and Zn2+ were 403.2, 191.6, and 54.0 mg/g, respectively, while Hg2+, Cd2+ and Zn2+ biosorption capacities of the immobilized live form were 333.0, 164.8 and 42.1 mg/g, respectively. The same affinity order on a molar basis was observed for single or multi-metal ions (Hg2+ > Cd2+ > Zn2+). The Langmuir and the Freundlich type models were found to exhibit good fit to the experimental data. The experimental data were analyzed using the first-order (Langergren equations) and the second order (Ritchie equations). The experimental biosorption capacity with time is found to be best fit the second-order equations. The alginate-fungus system could be regenerated by washing with a solution of hydrochloride acid (10 mM). The percent desorption achieved was as high as 97. The biosorbents were reused in five biosorption-desorption cycles without significant loss of their initial biosorption capacity. (C) 2004 Elsevier B.V. All rights reserved.
Biosorption of inorganic mercury and alkylmercury species on to Phanerochaete chrysosporium mycelium
(Elsevier Sci Ltd, 1999) Saglam, N; Say, R; Denizli, A; Patir, S; Arica, MY
The biosorption of inorganic mercury (HgCl2), methyl mercury (CH3HgCl) and ethyl mercury (C2H5HgCl) onto the dry biomass of Phanerochaete chryosponum was studied from aqueous media which concentrations in the range of 5-500 mg l(-1). The surface charge density varied with pH, and the concentration of mercury species adsorbed significantly increased from pH 3.0 to maximum levels at pH 8.0. The biosorption of mercury ions by Phanerochaete chrysosporium increased as the initial concentration of Hg(II) ion increased in the adsorption medium. A biosorption equilibrium were established after about 6 h, the adsorbed Hg(II) ion did not significantly change further with time. The dissociation constant (k(d)) values were 72, 63, and 61 mg l(-1) for CH3HgCl, C2H5HgCl and for Hg(II), respectively. The maximum biosorption capacity (q(m)) at pH 7.0 was 79 mg for CH3HgCI, 67 mg for C2H5HgCl and 61 mg for Hg(II) per g of dried fungal biomass. The affinity order of mercury species was CH3HgCl > C2H5HgCl > and Hg(II). (C) 1999 Elsevier Science Ltd. All rights reserved.
Catalase adsorption onto cibacron blue F3GA and Fe(III)derivatized poly(hydroxyethyl methacrylate) membranes and application to a continuous system
(Elsevier Science Bv, 1997) Arica, MY; Denizli, A; Salih, B; Piskin, E; Hasirci, V
Poly(2-hydroxyethyl methacrylate) (poly(HEMA)) membranes were prepared by W-initiated photopolymerization of HEMA in the presence of an initiator (a-a'-azobisisobutyronitrile, AIBN). An affinity dye, i.e. Cibacron Blue F3GA (CB) was incorporated covalently and then complexed with Fe(III) ions. The polyHEMA-CB and polyHEMA-CB-Fe(III) derivatized membranes were used in the adsorption of catalase (CAT). The enzyme-loading capability of the Fe(III)-containing membrane (23.6 mu g/cm(2)) was greater than that of the poly(HEMA)-CB derivatized membrane (17.1 mu g/cm(2)). The adsorption phenomena appeared to follow a typical Langmuir isotherm. The K-m values for both immobilized catalases (poly(HEMA)-CB-CAT (22.4 mM) and poly(HEMA)-CB-Fe(III)-CAT (19.3 mM)) were higher than that of free enzyme (16.5 mM). Optimum operational temperature was 5 degrees C higher than that of the free enzyme and was significantly broader. A similar observation was made for the optimum pH. Operational, thermal and storage stabilities were found to increase with immobilization, especially in the presence of Fe(III). It was observed that enzyme could be repeatedly adsorbed and desorbed without significant loss in adsorption capacity or enzyme activity.
Characterisation of tyrosinase immobilised onto spacer-arm attached glycidyl methacrylate-based reactive microbeads
(Elsevier Sci Ltd, 2004) Arica, MY; Bayramoglu, G; Bicak, N
Immobilisation of tyrosinase onto modified poly(methyl methacrylate-glycidyl methacrylate-divinyl benzene), poly(MMA-GMA-DVB), microbeads was studied. The epoxy group containing poly(MMA-MMA-DVB) microbeads were prepared by suspension polymerisation. The epoxy groups of the poly(MMA-GMA-DVB) microbeads was converted into amino groups with either ammonia or 1,6-diaminohexane (i.e., spacer-arm). Tyrosinase was then covalently immobilised on aminated and the spacer-arm-attached poly(MMA-GMA-DVB) microbeads using glutaric dialdehyde as a coupling agent. Incorporation of the spacer-arm resulted an increase in the apparent activity of the immobilised tyrosinase with respect to the enzyme immobilised on the aminated microbeads. The activity yield of the immobilised tyrosinase on the spacer-arm-attached poly(MMA-GMA-DVB) microbeads was 68%, and this was 51% for the enzyme, which was immobilised on the aminated microbeads. Both immobilised tyrosinase preparation has resistance to temperature inactivation as compared to that of the free form. The temperature profiles were broader for both immobilised preparations than that of the free enzyme. Kinetic parameters were determined for immobilised tyrosinase preparations as well as for the free enzyme. The values of the Michaels constants (K-m) for all the immobilised tyrosinase preparations were significantly larger, indicating decreased affinity by the enzyme for its substrate, whereas V-max values were smaller for the both immobilised tyrosinase preparations. In a 40 h continuous operation with spacer-arm-attached poly(MMA-GMA-DVB) microbeads at 30degreesC, only 3% of immobilised tyrosinase activity was lost. The operational inactivation rate constant (k(opi)) of the immobilised tyrosinase was 1.25 x 10(-5) min(-1). (C) 2003 Elsevier Ltd. All rights reserved.
Characterization of β-galactosidase immobilized into poly(hydroxyethylmethacrylate) membranes
(Mbr Press Inc, 1998) Adali, O; Baran, T; Arica, MY
beta-galactosidase was immobilized into pHEMA membranes with the highest specific activity yield of 9.5%. The specific activity of the entrapped enzyme was found to be decreased as the enzyme loading increased in pHEMA membranes. The optimum pH and temperature for maximum activity of the immobilized beta-galactosidase was found to be at pH 7.5 and 50 degrees C, respectively, and were the same as native enzyme. K-m and V-max values for the free enzyme were found to be 0.256 mM and 26.6 mu mole/min/mg, respectively. K-m value of immobilized beta-galactosidase was found to be increased about 3 folds upon immobilization. Operational, thermal and storage stability of beta-galactosidase were found to increase with immobilization. Immobilized enzyme preparation was reused in 15 cycles without significant loss in activity.
Cibacron Blue F3GA and Cu(II) derived poly(2-hydroxyethylmethacrylate) membranes for lysozyme adsorption
(Elsevier Science Bv, 1998) Denizli, A; Senel, S; Arica, MY
Lysozyme adsorption onto Cibacron Blue F3GA and Cu(II) derived poly(2-hydroxyethyl methacrylate) [poly(HEMA)] membranes was investigated. Microporous poly(HEMA) membranes were prepared by photopolymerization of HEMA. The triazine dye, Cibacron Blue F3GA was attached covalently as a dye-ligand. These dye-membranes with a swelling ratio of 58% (w/w), and carrying different amounts of Cibacron Blue F3GA (between 0.35 and 1.07 mu mol cm(-2)) were used in the lysozyme adsorption studies. The effect of initial concentration and pH on the adsorption efficiency of dye-derived and metal-chelated membranes were studied in a batch reactor. The effect of Cu(II) incorporation on lysozyme adsorption was also studied. The non-specific adsorption of lysozyme on the poly(HEMA) membranes was 0.9 mu g cm(-2). Cibacron Blue F3GA attachment significantly increased the lysozyme adsorption up to 133.3 mu gcm(-2) Lysozyme adsorption capacity of the Cu(II) incorporated membranes (165.1 mu g cm(-2)) was greater than that of the Cibacron Blue F3GA-attached membranes. More than 85% of the adsorbed lysozyme was desorbed in 1 h in the desorption medium containing 0.5 M potassium thiocyanate (KSCN) at pH 8.0. (C) 1998 Elsevier Science B.V. All rights reserved.
Cibacron Blue F3GA-incorporated macroporous poly(2-hydroxyethyl methacrylate) affinity membranes for heavy metal removal
(Elsevier Science Bv, 1997) Denizli, A; Salih, B; Arica, MY; Kesenci, K; Hasirci, V; Piskin, E
Macroporous poly(2-hydroxyethyl methacrylate), poly(HEMA), membranes were prepared by UV-initiated photo-polymerization of HEMA in the presence of an initiator (azobisisobutyronitrile, AIBN). An affinity dye, i.e., Cibacron Blue F3GA was then incorporated covalently. These affinity membranes with a swelling ratio of 58%, and carrying 10.67 mmol Cibacron Blue F3GA/m(2) membrane were used in the adsorption/desorption of some selected heavy metal ions [i.e., As(III), Cd(II) and Pb(II)] from aqueous media. Very high adsorption rates were observed and adsorption equilibria were reached in about 30 min. The maximum adsorptions of heavy metal ions onto the dye-incorporated affinity membranes from their single solutions were 12.6 mmol/m(2) for As(III), 61.0 mol/m(2) for Cd(II) and 79.0 mol/m(2) for Pb(II), However, when the heavy metal ions competed (in the case of the adsorption from their mixture) the amounts of adsorption for As(III), Cd(II) and Pb(II) were quite close. Desorption of heavy metal ions was carried out by using 0.1 M HNO3 (pH 1.0). Up to 95% of the adsorbed heavy metal ions were desorbed in 60 min. Repeated adsorption/desorption cycles showed the feasibility of this novel affinity membrane for heavy metal removal.
Comparison of β-galactosidase immobilization by entrapment in and adsorption on poly(2-hydroxyethylmethacrylate) membranes
(John Wiley & Sons Ltd, 1997) Baran, T; Arica, MY; Denizli, A; Hasirci, V
beta-Galactosidase was immobilized in/on poly(2-hydroxyethyl methacrylate) (pHEMA) membranes by two different methods: adsorption on Cibacron F3GA derivatized pHEMA membranes (pHEMA-CB), and entrapment in the bulk of the pHEMA membranes. The maximum beta-galactosidase adsorption on pHEMA-CB membranes was obtained as 95.6 mu g cm(-2) in 2.0 mg cm(-3) enzyme solution. The adsorption phenomena appeared to follow a typical Langmuir isotherm. In the entrapment, an increase in beta-galactosidase loading resulted in a consistent increase in membrane activity from 3.3 x 10(-2) to 17.8 x 10(-2) U cm(-2) pHEMA membranes. The K-m values for both immobilized beta-galactosidase (adsorbed 0.32 mM and entrapped 0.81 mM) were higher than that of the free enzyme (0.26 mM). The optimum reaction temperature of the adsorbed enzyme was 5 degrees C higher than that of both the free and the entrapped enzyme. The optimum reaction pH was 7.5 for free and both immobilized preparations. After 15 successive uses the retained activity of the adsorbed and the entrapped enzymes was 80% and 95%, respectively. The storage stability of the enzyme was found to increase upon immobilization.
Controlled release of aldicarb from carboxymethyl cellulose microspheres: in vitro and field applications
(John Wiley & Sons Ltd, 1999) Kok, FN; Arica, MY; Gencer, O; Abak, K; Hasirci, V
Aldicarb is a carbamate pesticide that is widely used throughout the world in the protection Of crops (eg cotton, nuts, potatoes, onion, tobacco, sugar beet and sugar cane). In Turkey, especially in the Cukurova region, it is used for the control of the cotton white fly (Bemisia tabaci) which attacks cotton plants cultivated in this region. Aldicarb contamination in surface and ground water is a serious problem in several countries, partly due to its high water solubility. It is also highly toxic to mammals. In order to overcome these problems, microspheres of aldicarb were prepared using carboxymethyl cellulose (CMC) as the biodegradable support material cross-linked with aluminium chloride. A strong hysteresis behaviour was observed upon drying and reswelling. Encapsulation efficiency was in the range 12-23% and aldicarb contents of 5.7-10.3 mg per 100mg of microspheres was achieved. In vitro release was distinctly Fickian, and Higuchi constants were very close to 0.5. Release in pots revealed that only one sample had a release capability for more than four weeks. In the cotton plot much longer durations of release (more than seven weeks) were observed while a commercial granular formulation released its content immediately. It was thus possible to construct a controlled pesticide release system that prolonged the bioavailability to about eight weeks. (C) 1999 Society of Chemical Industry.
Controlled release of Aldicarb from carboxymethylcellulose microcapsules
(Scientific Technical Research Council Turkey, 1997) Arica, MY; Yigitoglu, M; Lale, M; Kok, FN; Hasirci, V
Sodium carboxymethyl cellulose was converted into microspheres by crosslinking with aluminum chloride. Various microsheres with different amounts of crosslinker, biopolymer of various concentrations and molecular weights, and with different pesticide (Aldicarb) contents and pesticide to polymer ratios were prepared. The pesticide encapsulation efficiencies and aldicarb release kinetics of the resultant microcapsules were investigated. It was possible to modify the release behaviour by varying the above parameters and to have drug release with half-lives longer than 100 hours in aqueous media. The release kinetics were described by first order and zero order kinetics.
Controlled release of aldicarb from lignin loaded ionotropic hydrogel microspheres
(Taylor & Francis Ltd, 1999) Kok, FN; Wilkins, RM; Cain, RB; Arica, MY; Alaeddinoglu, G; Hasirci, V
Aldicarb loaded microspheres of carboxymethyl cellulose, CMC, of various compositions were prepared with the crosslinking action of AI(III). Into these microspheres, lignin was introduced as a filler to further regulate the rate of release. The encapsulation efficiency was low (4.15-13.00%) due to the high water solubility of aldicarb. Release into aqueous media was quite rapid and almost complete within 24h. Initial stages of the release (60% of AS released) was investigated to determine the release mechanism and it was found that release from the microspheres was governed by Fickian diffusion. Among the various parameters, the ratio of lignin to CMC and aldicarb to CMC were found to be influential on the rate of release from the crosslinked CMC-lignin microspheres. The soil behaviour confirmed the delayed release effect of the controlled release formulation compared to Temik (a commercial preparation of aldicarb), especially when lignin was incorporated.
Covalent immobilisation of invertase onto a reactive film composed of 2-hydroxyethyl methacrylate and glycidyl methacrylate: properties and application in a continuous flow system
(Elsevier Science Sa, 2003) Bayramoglu, G; Akgol, S; Bulut, A; Denizli, A; Arica, MY
Invertase was covalently immobilised on the poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) (poly(HEMA-GMA)) film. The invertase immobilisation capacity of the films was increased as the GMA ratio increased in the film structure. The immobilised invertase on the poly(HEMA-GMA-3) composition exhibited an activity of 32.7 U cm(-2) film. The optimum temperature of the immobilised invertase increased by 5 degreesC, and the optimal pH values for the free and the immobilised enzymes were determined as 5.0. The retained activity of the immobilised invertase was between 53 and 85%. Kinetic parameters were determined for immobilised invertase as well as for the free enzyme. The values of the Michael's constant K-m of invertase were significantly larger, ca. 2.7 times upon immobilisation, indicating decreased affinity by the enzyme for its substrate, whereas V-max was smaller for immobilised invertase. Activity of the immobilised invertase was quite stable with respect to free counterpart. After 168 h reaction, only 8% of immobilised invertase activity was lost. The operational inactivation rate constant (k(opi)) of the immobilised invertase at 35 degreesC with 200 mM sucrose was 8.23 x 10(-6) min(-1). (C) 2002 Elsevier Science B.V. All rights reserved.
Dye affinity poly(2-hydroxyethyl methacrylate) membranes for removal of heavy metal ions
(Marcel Dekker Inc, 2000) Denizli, A; Say, R; Arica, MY
The dichlorotriazinyl dye-ligand Procion Red HE-3B-anchored poly(EGDMA-HEMA) membranes were used for removal of heavy metal ions (i.e., copper, arsenic, cadmium and mercury) from aqueous media containing different amounts of these ions (0.1-4.5 mmol/L) and at different pH values (2.0-8.0). The HE-3B-anchored membranes from their single solutions were 6.4 mmol/m(2) for Cu(II), 30.1 mmol/m(2) for As(III), 76.3 mmol/m(2) for Cd(II) and 130.3 mmol/m(2) for Hg(II). When the heavy metal ions competed tin the case of the adsorption from their mixture) the adsorption capacities were 7.8 mmol/m(2) fur Cu(II), 24.5 mmol/m(2) for As(III), 27.6 mmol/m(2) for Cd(II) and 42.3 mmol/m2 for Hg(II). The same affinity order was observed under non-competitive and competitive adsorption which was as follows: Hg(II) > Cd(II) > As(III) > Cu(IT). The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 5.0. Heavy metal ion adsorption from artificial wastewater was also studied. The adsorption capacities are 4.1 mmol/m(2) for Cu(II), 12.5 mmol/m(2) for As(III), 16.7 mmol/m(2) for Cd(II) and 21.3 mmol/m(2) for Hg(II). Desorption of heavy metal ions was achieved using 0.1 M HNO3. The Procion Red HE-3B-anchored membranes are suitable for repeated use for more than 5 cycles without noticeable loss of capacity.
Dye derived and metal incorporated affinity poly(2-hydroxyethyl methacrylate) membranes for use in enzyme immobilization
(John Wiley & Sons Ltd, 1998) Arica, MY; Denizli, A; Baran, T; Hasirci, V
Microporous poly(2-hydroxyethyl methacrylate) (PHEMA) membranes were prepared by W-initiated photopolymerization of HEMA in the presence of an initiator (alpha,alpha'-azobisisobutyronitrile, AIBN). An affinity dye Cibacron Blue F3GA (CB) was attached covalently and then Fe3+ ions incorporated. The PHEMA-CB and PHEMA-CB-Fe3+ membranes derived were used for adsorption of glucose oxidase (GOD). The adsorption capacities of these membranes were determined under conditions of different pH and with different concentrations of the adsorbate in the medium. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The glucose oxidase adsorption capacity of the Fe3+ incorporated membrane (87 mu g cm(-2)) was greater than that of the dye-derived membrane (66 mu g cm(-2)). Non-specific adsorption of the glucose oxidase on the PHEMA membranes was negligible. The K-m values for both immobilized glucose oxidase PHEMA-CB-GOD (8.3) and PHEMA-CB-Fe3+-GOD (7.6) were higher than that of the free enzyme (6.2 mM). Optimum reaction pH was 5.5 for the free and 6.0 for both immobilized preparations. The optimum reaction temperature of the adsorbed enzymes was 5 degrees C higher than that of the free enzyme and was significantly broader. After 15 successive uses the retained activity of the adsorbed enzyme was 87%. It was observed that enzymes could be repeatedly adsorbed and desorbed on the derived PHEMA membranes without significant loss in adsorption capacity or enzymic activity. (C) 1998 SCI.

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