Nadir Dizge

Biodiesel production from sunflower, soybean, and waste cooking oils by transesterification using lipase immobilized onto a novel microporous polymer.

This study aims at carrying out lipase-catalyzed synthesis of fatty acid methyl esters (biodiesel) from various vegetable oils using lipase immobilized onto a novel microporous polymeric matrix (MPPM) as a low-cost biocatalyst. The research is focused on three aspects of the process: (a) MPPM synthesis (monolithic, bead, and powder forms), (b) microporous polymeric biocatalyst (MPPB) preparation by immobilization of lipase onto MPPM, and (c) biodiesel production by MPPB. Experimental planning of each step of the study was separately carried out in accordance with design of experiment (DoE) based on Taguchi methodology. Microporous polymeric matrix (MPPM) containing aldehyde functional group was synthesized by polyHIPE technique using styrene, divinylbenzene, and polyglutaraldehyde. Thermomyces lanuginosus lipase was covalently attached onto MPPM with 80%, 85%, and 89% immobilization efficiencies using bead, powder, and monolithic forms, respectively. Immobilized enzymes were successfully used for the production of biodiesel using sunflower, soybean, and waste cooking oils. It was shown that immobilized enzymes retain their activities during 10 repeated batch reactions at 25 degrees C, each lasting 24h. Since the developed novel method is simple yet effective, it could have a potential to be used industrially for the production of chemicals requiring immobilized lipases.

Sorption of Ni(II) ions from aqueous solution by Lewatit cation-exchange resin

Ion-exchange is an alternative process for uptake of heavy metals from aqueous solutions. In the present study, the sorption of nickel(II) ions from aqueous solution was investigated by using Lewatit MonoPlus SP 112 (strongly acidic, macroporous cation-exchange resin) in a batch adsorption system as a function of pH (2.0-8.0), initial nickel concentration (50-200 mg/L), resin dosage (0.5-2.0 g/L), contact time (0.5-3h), and temperatures (298-318K). The data were analyzed on the basis of Lagergren pseudo-first order, pseudo-second order (Types 1-5), Elovich and external, Weber-Morris intraparticle, pore-surface mass diffusion models. The experimental data showed that the maximum pH for efficient sorption of nickel(II) was 6.0. At the optimal conditions, nickel(II) ions sorption on the resin was decreased when the initial metal concentration increased. The results indicated that the resin dosage strongly affected the amount of nickel(II) ions removed from aqueous solution. The adsorption process was very fast due to 80% of nickel(II) sorption was occurred within 30 min and equilibrium was reached at about 90 min. Freundlich and Langmuir adsorption isotherm models were used for sorption equilibrium data and the maximum adsorption capacity (171 mg/g) of Lewatit MonoPlus SP 112 was obtained from Langmuir isotherm. The thermodynamic parameters (DeltaG degrees, free energy change; DeltaS degrees, enthalpy change; and DeltaH degrees, entropy change) for sorption of nickel(II) ions were evaluated. The rise in temperature caused a partly increase in the value of the equilibrium constant (K(c)) for the sorption of nickel(II) ions. Moreover, column flow adsorption study was also studied. Breakthrough curves were obtained from column flow studies by using both synthetic solution and rinsing bath water of filter industry. The column regeneration was carried out for two sorption-desorption cycles. The eluant used for regeneration of the cation-exchange resin was 7% (w/w) HCl. The experimental results demonstrated that Lewatit MonoPlus SP 112 cation-exchange resin could be used effectively for the removal of nickel(II) ions from aqueous medium.

Covalent attachment of microbial lipase onto microporous styrene–divinylbenzene copolymer by means of polyglutaraldehyde

A novel method for immobilization of Thermomyces lanuginosus lipase onto polyglutaraldehyde-activated poly(styrene-divinylbenzene) (STY-DVB), which is a hydrophobic microporous support has been successfully developed. The copolymer was prepared by the polymerization of the continuous phase of a high internal phase emulsion (polyHIPE). The concentrated emulsion consists of a mixture of styrene and divinylbenzene containing a suitable surfactant and an initiator as the continuous phase and water as the dispersed phase. Lipase from T. lanuginosus was immobilized covalently with 85% yield on the internal surface of the hydrophobic microporous poly(styrene-divinylbenzene) copolymer and used as a biocatalyst for the transesterification reaction. The immobilized enzyme has been fully active 30 days in storage and retained the activity during the 15 repeated batch reactions. The properties of free and immobilized lipase were studied. The effects of protein concentration, pH, temperature, and time on the immobilization, activity, and stability of the immobilized lipase were also studied. The newly synthesized microporous poly(styrene-divinylbenzene) copolymer constitutes excellent support for lipase. It given rise to high immobilization yield, retains enzymatic activity for 30 days, stable in structure and allows for the immobilization of large amount of protein (11.4mg/g support). Since immobilization is simple yet effective, the newly immobilized lipase could be used in several application including oil hydrolysis, production of modified oils, biodiesel synthesis, and removal of fatty acids from oils.

Removal of thiocyanate from aqueous solutions by ion exchange

The adsorption kinetics and equilibrium of thiocyanate in aqueous solutions onto an anion-exchange resin (Purolite A-250) were investigated in a batch-mode operation to assess the possible use of this adsorbent. The effect of various parameters such as initial thiocyanate concentration, contact time, pH, particle size, resin dosage and temperature were studied. A comparison of four kinetic models, the pseudo-first-order, second-order, Elovich and diffusion controlled kinetic models, on the thiocyanate-resin system was used to determine the rate constants and the adsorption mechanism. The kinetic results correlated well with pseudo-second-order model. The experimental parameters had also an effect on the pore and surface diffusivities. The optimum conditions for removal of thiocyanate were found to be pH 8, 2g/l of adsorbent dosage, 355-500 microm of particle size and equilibrium time of 30 min, respectively. The column capacity and performance by the bed depth service time model using bed depth and flow rate as variables were evaluated. The adsorption isotherm data were fitted well to Langmuir and Freundlich isotherms. The adsorption capacity was calculated as 191.20mg/g at 323 K. Thermodynamics parameters such as free Delta G(0), Delta H(0) and DeltaS(0) for the adsorption were evaluated. The positive value of Delta H(0) indicated that the process was endothermic in nature.

Biodegradation characteristics and size fractionation of landfill leachate for integrated membrane treatment.

The fate of organics and nitrogen during the biological treatment with MBR and subsequent membrane filtration processes (nano filtration, NF; reverse osmosis, RO) were investigated for a landfill leachate. The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal performances of membrane bioreactor (MBR) were obtained to be around 89% and 85%, respectively. The effluent COD of MBR was measured to be 1935 mg/L (30 kDa) which is much lower than experimentally determined soluble inert COD of 3200 mg/L using 0.45 μm filter. The readily and slowly biodegradable COD fractions were estimated to be 17% and 52% of raw influent COD, respectively. The respirometry based modeling test performed on raw leachate exhibited much slower degradation kinetics compared to municipal wastewater. A unique subset of model parameters was extracted from batch respirometry by using acclimated MBR sludge. The sequential ultrafiltration (UF) experiments (particle size distribution, PSD) revealed that most of the organics was below 2 nm filter mesh size. In addition, NF/RO post treatment after MBR system was required to increase COD and total nitrogen (TN) removal performances up to 99%. Relatively lower salt rejection rates around 94% was obtained for RO system as a post treatment of MBR system.

Enzymatic activation of cellulose acetate membrane for reducing of protein fouling

In this study, the surface of cellulose acetate (CA) ultrafiltration membrane was activated with serine protease (Savinase) enzyme to reduce protein fouling. Enzyme molecules were covalently immobilized with glutaraldehyde (cross-linking agent) onto the surface of CA membranes. The membrane activation was verified using filtration experiments and morphological analysis. Scanning electron microscopy (SEM) images and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy of the activated membrane when compared with raw membrane were confirmed that the enzyme was immobilized onto the membrane surface. The immobilization efficiencies changed from 13.2 to 41.2% according to the enzyme ratios from 2.5 to 10.0 mg/mL. However, the permeability values decreased from 232±6 to 121±4 L/m(2) h bar with increasing enzyme concentration from 2.5 to 10.0 mg/mL. In fouling experiments, bovine serum albumin (BSA) was used as the protein model solution and activated sludge was used as the model biological sludge. Enzyme-activated membranes exhibited good filtration performances and protein rejection efficiencies were compared with raw CA membrane. Also the relative flux reduction (RFR) ratios of membranes were calculated as 97% and 88% for raw CA and enzyme-activated membranes (5 mg/mL savinase), respectively. The membrane activated with Savinase enzyme could be proposed as a surface treatment method before filtration to mitigate protein fouling.

Immobilization of Candida antarctica A and Thermomyces lanuginosus lipases on cotton terry cloth fibrils using polyethyleneimine

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 °C) was studied. It was found that immobilization had no effect on the optimum temperature and it was 60 °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.

A novel implementation of water recovery from whey: “forward–reverse osmosis” integrated membrane system

Abstract As a result of its emerging contribution to water recovery and clean water production, forward osmosis (FO) in integrated membrane system has recently especially been preferred by research communities on membrane science and desalination technology. In this study, the effectiveness of FO reverse osmosis (RO) integrated membrane system in whey dewatering was investigated in laboratory scale experiments in which FO and RO were utilized for whey concentration and water recovery, respectively. FO experiments were carried out at different conditions of cross-flow rate, temperature, membrane kind, membrane orientation mode, and microfiltration (MF) pretreatment. A single-step RO system was applied for water recovery from the FO draw solution. In the FO process, about 1.6 L water of 3 L whey was withdrawn into 3 M NaCl draw solution during 6 h operating time, and a sufficiently high performance in whey concentration was obtained, with the solid content being increased from 6.8 to 14.3%. However, the pro...

Multiparametric investigation of competitive and noncompetitive sorption characteristics of SMP fractions (carbohydrate and protein) on activated carbon.

Sorption characteristics of soluble microbial products (SMPs) as carbohydrate and protein on activated carbon were investigated. Batch experiments were conducted to evaluate the sorption kinetics and the equilibrium conditions. The parameters studied included initial SMP concentration (50-200mg/L), activated carbon dosage (0.25-50 g/L), contact time (0.02-4h), particle size of activated carbon used (5-75 μm, 75-850 μm, and 850-1000 μm), and presence of one or both SMP fractions. The equilibrium sorption of carbohydrate and protein were significantly affected by the presence of the second SMP fraction in the solutions. Adsorption isotherms were expressed by the Langmuir and Freundlich models. The adsorption rates under noncompetitive and competitive conditions were analyzed with kinetics-based Lagergren pseudo-first order and pseudo-second order models; and diffusion-based external diffusion and Weber-Morris intraparticle models. Both SMP fractions were removed effectively, however, sorption of protein was significantly better than that of carbohydrate in all cases. The relatively significant effect of particle size on sorption of protein indicates that protein is most likely adsorbed as a single layer on the carbon surface. For the carbohydrate, the increase in particle size did not decrease the sorption significantly indicating that carbohydrate may be adsorbed in multiple layers or may diffuse into the porous matrix more effectively.

External mass transfer analysis for simultaneous removal of carbohydrate and protein by immobilized activated sludge culture in a packed bed batch bioreactor.

External mass transfer effects were analyzed for removal of carbohydrate and protein by immobilized activated sludge culture in a packed bed bioreactor. The bioreactor was made from 52 cm glass tubing with 5.0 cm inner diameter (with a total volume of 1020 cm(3)). The microbial culture was immobilized on microporus polyurethane cut into cubic pieces of approximately 1.5 cm in length. The effect of flow rate on mass transfer and removal of carbohydrate and protein were analyzed theoretically and compared with experimental data. The rate constants were estimated using external film diffusion models at different flow rates (900, 1200, 1800 cm(3)h(-1)). Based on the experimental data, correlations between the Colburn factor (J(D)) and Reynolds number (Re) as J(D)=5.7 × Re(-0.90) and J(D)=5.7 × Re(-0.18) were found to be adequate to predict the removal of carbohydrate and protein, respectively.