Use of chitosan for removal of bisphenol A and bisphenol derivatives through tyrosinase‐catalyzed quinone oxidation

In this study, the availability of chitosan was systematically investigated for removal of bisphenol A (BPA, 2,2‐bis(hydroxyphenyl)propane) through the tyrosinase‐catalyzed quinone oxidation and subsequent quinone adsorption on chitosan beads. In particular, the process parameters, such as the hydrogen peroxide (H₂O₂)‐to‐BPA ratio, pH value, temperature, and tyrosinase dose, were discussed in detail for the enzymatic quinone oxidation. Tyrosinase‐catalyzed quinone oxidation of BPA was effectively enhanced by adding H₂O₂ and the optimum conditions for BPA at 0.3 mM were determined to be pH 7.0 and 40°C in the presence of H₂O₂ at 0.3 mM ([H₂O₂]/[BPA] = 1.0). Removal of BPA from aqueous solutions was accomplished by adsorption of enzymatically generated quinone derivatives on chitosan beads. The use of chitosan in the form of beads was found to be more effective because heterogeneous removal of BPA with chitosan beads was much faster than homogeneous removal of BPA with chitosan solutions, and the removal efficiency was enhanced by increasing the amount of chitosan beads dispersed in the BPA solutions and BPA was completely removed by quinone adsorption in the presence of chitosan beads more than 0.10 cm³/cm³. In addition, a variety of bisphenol derivatives were completely or effectively removed by the procedure constructed in this study, although the enzyme dose or the amount of chitosan beads was further increased as necessary for some of the bisphenol derivatives used. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Immobilization of horseradish peroxidase on chitosan for use in nonaqueous media

Chitosan, a natural polysaccharide, was used for the covalent immobilization of horseradish peroxidase, an enzyme of high synthetic utility, with the carbodiimide method. Of the enzyme, 62% was immobilized on chitosan when 1‐ethyl‐3‐(3‐dimethylaminopropyl carbodiimide) was used as the peptide coupling agent. The influence of different parameters, such as the enzyme concentration, carbodiimide concentration, and incubation period, on the activity retention of the immobilized enzyme was investigated. Kinetic studies using horseradish peroxidase immobilized on chitosan revealed the effects of several parameters, such as the substrate hydrophilicity and hydrophobicity, the solubility of substrates in the medium, the solvent hydrophobicity, and the support aquaphilicity, on the catalytic activity of the immobilized enzyme in nonaqueous media. General rules for the optimization of solvents for nonaqueous enzymology based on the partitioning of the solvent were not applicable for the immobilized horseradish peroxidase. The catalytic efficiency was greatest when o‐phenylene diamine was used as the substrate and least when guaiacol was used. The aquaphilicity of the support played an important role in the kinetics of the immobilized horseradish peroxidase in water‐miscible solvents. The results were promising for the future development of chitosan‐immobilized enzymes for use in organic media. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1456–1464, 2003     

Application of enzymatically gelled chitosan solutions to water‐resistant adhesives

An investigation was undertaken on the application of dilute chitosan solutions gelled by tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenethylamine (dopamine). The tyrosinase‐catalyzed reaction with dopamine conferred water‐resistant adhesive properties to the semidilute chitosan solutions. The viscosity of the chitosan solutions increased highly by the tyrosinase‐catalyzed reaction and the subsequent reactions between o‐quinone compounds and chitosan. These highly viscous, gel‐like modified chitosan materials were allowed to spread onto the surfaces of the glass slides, which were tightly lapped together and held them in water. Tensile shear adhesive strength of over 400 kPa was observed for the modified chitosan samples. The increase in the amino group concentration of the chitosan solutions and the molecular mass of the chitosan used effectively led to the increase in adhesive strength of the glass slides. In addition, in the case where the chitosan solution was gelled by the enzymatic reaction with dopamine in the presence of poly(ethylene glycol), adhesive strength sharply increased at shorter reaction times concomitantly with the increase in the viscosity of the chitosan solutions because the tyrosinase activity effectively was retained by poly(ethylene glycol). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1818–1827, 2007     

Use of chitosan for removal of bisphenol a from aqueous solutions through quinone oxidation by polyphenol oxidase

In this study, a combined use of biopolymer chitosan and oxidoreductase polyphenol oxidase (PPO) was applied to the removal of bisphenol A (BPA) as an endocrine disrupting chemical from aqueous solutions. The optimum conditions for the enzymatic quinone oxidation of BPA were determined to be pH 7.0 and 40°C. Quinone derivatives generated were chemisorbed on chitosan beads, and BPA was completely removed at 4–7 h. The removal time was shortened with an increase in the amount of dispersed chitosan beads or the PPO concentration. In addition, the initial velocity of quinone oxidation increased with an increase in the amount of chitosan beads. The use of chitosan in the form of porous beads was more effective than the use of chitosan in the form of solutions or powder. It was found that an important factor for this procedure was a high‐specific surface area of chitosan beads and heterogeneous reaction of quinone derivatives enzymatically generated with chitosan. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synergistic effects of crosslinking and chitosan molecular weight on the microstructure,molecular mobility,thermal and sorption properties of porous chitosan/gelatin/hyaluronic acid scaffolds

In this study, synergistic effects of crosslinking and chitosan molecular weight on the microstructure, molecular mobility, thermal, and sorption properties of porous chitosan/gelatin/hyaluronic acid hybrid foams are reported. Fourier transform infrared spectroscopy has been utilized to confirm the covalent attachment of hyaluronic acid to gelatin and chitosan, and covalent chemical crosslinking between gelatin and chitosan. Detailed image analysis of scanning electron microscopy images of the porous scaffold hydrids reveal that the pore size of the materials formulated using either low‐ or high‐molecular‐weight chitosan increases significantly upon crosslinking using ethyl(dimethylaminopropyl) carbodiimide/N‐Hydroxysuccinimide. These microstructural changes are even more pronounced for the crosslinked hybrid scaffolds formulated using low‐molecular‐weight chitosan, highlighting a synergistic effect between crosslinking and the use of low‐molecular‐weight chitosan. Results obtained using differential scanning calorimetry demonstrate a significant reduction in molecular mobility reduction in molecular mobility for crosslinked scaffolds formed using high‐molecular‐weight chitosan compared to non‐crosslinked hybrids and crosslinked hybrids formulated using low‐molecular‐weight chitosan. Correspondingly, dynamic vapor sorption evidenced significantly lower water vapor sorption for crosslinked scaffolds formulated using high‐molecular‐weight chitosan. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44772.     

Application of chitosan solutions gelled by melB tyrosinase to water‐resistant adhesives

An investigation was undertaken on the application of dilute chitosan solutions gelled by melB tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenethylamine (dopamine). The tyrosinase‐catalyzed reaction with dopamine conferred water‐resistant adhesive properties to the semi‐dilute chitosan solutions. The viscosity of the chitosan solutions highly increased by the tyrosinase‐catalyzed quinone conversion and the subsequent nonenzymatic reactions of o‐quinones with amino groups of the chitosan chains. The viscosity of chitosan solutions highly increased in shorter reaction times by addition of melB tyrosinase. Therefore, in this study, the gelation of a chitosan solution was carried out without poly(ethylene glycol) (PEG), which was added for the gelation of chitosan solutions using mushroom tyrosinase. The highly viscous, gel‐like modified chitosan materials were allowed to spread onto the surfaces of the glass slides, which were tightly lapped together and were held under water. Tensile shear adhesive strength of over 400 kPa was observed for the modified chitosan samples. An increase in either amino group concentration of the chitosan solutions or molecular mass of the chitosan samples used effectively led to an increase in adhesive strength of the glass slides. Adhesive strength obtained by chitosan materials gelled enzymatically was higher than that obtained by a chitosan gel prepared with glutaraldehyde as a chemical crosslinking agent. In addition, the use of melB tyrosinase led to a sharp increase in adhesive strength in shorter reaction times without other additives such as PEG. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of chitosan‐coated magnetite nanoparticles and application for immobilization of laccase

In this study, immobilization of laccase (L) enzyme on magnetite (Fe₃O₄) nanoparticles was achieved, so that the immobilized enzyme could be used repeatedly. For this purpose, Fe₃O₄ nanoparticles were coated and functionalized with chitosan (CS) and laccase from Trametes versicolor was immobilized onto chitosan‐coated magnetic nanoparticles (Fe₃O₄‐CS) by adsorption or covalent binding after activating the hydroxyl groups of chitosan with carbodiimide (EDAC) or cyanuric chloride (CC). For chitosan‐coated magnetic nanoparticles, the thickness of CS layer was estimated as 1.0–4.8 nm by TEM, isoelectric point was detected as 6.86 by zeta (ζ)‐potential measurements, and the saturation magnetization was determined as 25.2 emu g^?1 by VSM, indicating that these nanoparticles were almost superparamagnetic. For free laccase and immobilized laccase systems, the optimum pH, temperature, and kinetic parameters were investigated; and the change of the activity against repeated use of the immobilized systems were examined. The results indicated that all immobilized systems retained more than 71% of their initial activity at the end of 30 batch uses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Stabilization of penicillin V acylase from Streptomyces lavendulae by covalent immobilization

Penicillin V acylase from the actinomycete Streptomyces lavendulae ATCC 13664 has been immobilized to epoxy‐activated acrylic beads (Eupergit C®) by covalent binding. Further linkage of bovine serum albumin after enzyme immobilization was carried out in order to remove the remaining oxirane groups of the support. The obtained immobilized biocatalyst displayed double exponential deactivation kinetics at temperatures below 55 °C, while the native enzyme followed single exponential decay at the same temperatures. We concluded that soluble penicillin acylase was deactivated in one step, whereas the immobilized enzyme showed an enzymatic intermediate state which is highly thermostable. As a consequence of the immobilization process, the enzyme displayed a 10‐fold increase in its half‐life at 40 °C. At this temperature, the enzymatic intermediate state was progressively destabilized as the pH of the medium was increased. Thus, the optimum pH range for the immobilized enzyme preparation was established as being from 7.0 to 8.0. Higher pH values led to quicker enzyme deactivation. © 2001 Society of Chemical Industry     

Cinnamic ester of D‐sorbitol for immobilization of mushroom tyrosinase

Mushroom tyrosinase was immobilized by adsorption onto the totally cinnamoylated derivative of D ‐sorbitol. The polymerization and cross‐linking of the derivative initially obtained was achieved by irradiation in the ultraviolet region, where this prepolymer shows maximum sensitivity. Immobilization of tyrosinase on this support involves a process of physical adsorption and intense hydrophobic interactions between the cinnamoyl groups of the support and related groups of the enzyme. The pH value, enzyme concentration and immobilization time were all important parameters affecting immobilization efficiency; also, enzyme immobilization efficiency correlated well with the tyrosinase isoelectric point. The immobilized enzyme showed an optimum measuring pH of 3.5 and greater activity at acid and neutral pH values than the soluble enzyme. The optimal reaction temperature was 35 °C and the temperature profile was broader than that of the free enzyme or of the enzyme immobilized on other supports. The apparent Michaelis constant of mushroom tyrosinase immobilized on the SOTCN derivative acting on 4‐tert‐butylcatechol (TBC) was 0.40 ± 0.02 mmol dm^?3, which was lower than for the soluble enzyme, suggesting that the affinity of this enzyme for this substrate was greater when immobilized than when in solution. Immobilization stabilized the enzyme and made it less susceptible to activity loss during storage at pH values in the range 4–5.5, and the suicide inactivation of the immobilized tyrosinase was null or negligible in a reaction medium with 4‐tert‐butylcatechol at a concentration of 0.4 mmol dm^?3. The results show that cinnamic carbohydrate esters of D ‐sorbitol are an appropriate support for tyrosinase immobilization and could be of use for several tyrosinase applications. Copyright © 2005 Society of Chemical Industry     

Chitosaneous hydrogel beads for immobilizing neutral protease for application in the preparation of low molecular weight chitosan and chito‐oligomers

Enzyme hydrolysis with immobilized neutral protease was carried out to produce low molecular weight chitosan (LMWC) and chito‐oligomers. Neutral protease was immobilized on (CS), carboxymethyl chitosan (CMCS), and N‐succinyl chitosan (NSCS) hydrogel beads. The properties of free and immobilized neutral proteases on chitosaneous hydrogel beads were investigated and compared. Immobilization enhanced enzyme stability against changes in pH and temperature. When the three different enzyme supports were compared, the neutral protease immobilized on CS hydrogel beads had the highest thermal stability and storage stability, and the enzyme immobilized on NSCS hydrogel beads had the highest activity compared to those immobilized on the other supports, despite its lower protein loading. Immobilized neutral protease on all the three supports had a higher K_m (Michaelis‐Menten constant) than free enzyme. The V_max (maximum reaction velocity) value of neutral protease immobilized on CS hydrogel beads was lower than the free enzyme, whereas the V_max values of enzyme immobilized on CMCS and NSCS hydrogel beads were higher than that of the free enzyme. Immobilized neutral protease on CS, CMCS, and NSCS hydrogel beads retained 70.4, 78.2, and 82.5% of its initial activity after 10 batch hydrolytic cycles. The activation energy decreased for the immobilization of neutral protease on chitosaneous hydrogel beads. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3743–3750, 2006     

Semi‐interpenetrating polymer network beads of crosslinked chitosan–glycine for controlled release of chlorphenramine maleate

Spherical, semi‐interpenetrating polymer network beads of chitosan and glycine, crosslinked with different concentrations of glutaraldehyde were prepared for controlled release of drugs. The structural and morphological studies of the beads were carried out with FTIR and SEM techniques. The swelling behavior of the beads at different time intervals was monitored in solutions of different pH. Structural changes of the beads in response to solution pH were put forward using the data obtained from IR/UV spectral analysis. The release experiments were performed in solutions of pH 2.0 and pH 7.4 at 37°C, using chlorphenramine maleate as a model drug. The results indicate that, chitosan might be useful as a vehicle for controlled release of drugs. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 672–683, 2000     

Immobilization of chitosan on nylon 6,6 and pet granules through hydrolysis pretreatment

Chitosan has been increasingly studied as an adsorbent for removing heavy metal ions and organic compounds from aqueous solutions. Most of the studies used chitosan in the form of flakes, powder, or hydrogel beads. This research investigates the immobilization of chitosan on other granular materials to overcome the poor mechanical property of chitosan and offers the potential for chitosan to be used as a regenerable adsorbent. Nylon 6,6 and poly(ethylene terephthalate) (PET) granules were partially hydrolyzed under an acidic or alkaline condition to allow chitosan to be coated or immobilized on the granules' surfaces. The surface morphologies of nylon 6,6 or PET granules before and after hydrolysis and those with immobilized chitosan layer were examined by scanning electron microscopy (SEM), and their surface properties were characterized through ζ‐potential analysis and X‐ray photoelectron spectroscopy. The immobilization of chitosan on nylon 6,6 or PET granules was identified to be through the formation of the salt structure (–NH…^?OOC–) between the surfaces of hydrolyzed nylon 6,6 or PET granules and the chitosan layer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3973–3979, 2003     

Chitosan‐treated polypropylene matrix as immobilization support for lactic acid production using Lactobacillus plantarum NCIM 2084

Adsorption coupled with electrostatic interaction as an immobilization technique is an important microbial cell immobilization technique. Treatment of the polymer matrix with the cationic surface treating agent chitosan for lactic acid production has been studied. Cells of Lactobacillus plantarum NCIM 2084 were immobilized on a polypropylene (PP) matrix treated with different concentrations of chitosan. The biocatalyst adsorbed on the 1.0 g dm^?3 chitosan‐treated PP matrix proved to be most effective. Repeated batch fermentation experiments showed that the immobilized biocatalyst could be recycled effectively 11 times. Studies were also carried out in a packed bed reactor with media recirculation. A high productivity of 7.66 g dm^?3 h^?1 could be obtained with a conversion of 94% and a yield of 97% at an average residence time of 30 h. © 2001 Society of Chemical Industry     

Stability of a chitosan layer deposited onto a polyethylene surface

A two‐step procedure was applied to obtain antimicrobial films; this procedure involved a corona treatment of the polyethylene (PE) surface and its chemical activation with 1‐ethyl‐3‐[3‐dimethylaminopropyl] carbodiimide hydrochloride and N‐hydroxysuccinimide, and this led to the covalent bonding of chitosan on the PE surface. Electrochemical methods were used to investigate the stability of the deposited chitosan layer. The potentiometric and polyelectrolyte titrations showed that some amount of chitosan desorbed faster from the surface until equilibrium was reached and also that the grafted chitosan layer was more stable than the physically adsorbed one. The chitosan immobilized on the PE surface exhibited the expected antibacterial activity when tested against three bacteria, which included two Gram‐negative bacteria, Salmonella enteritidis and Escherichia coli, and one Gram‐positive bacterium, Listeria monocytogenes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2444–2457, 2013     

Fabrication of a Chitosan‐Coated Magnetic Nanobiocatalyst for Starch Hydrolysis

The preparation of chitosan‐coated magnetic nanoparticles (MNPs) and covalent immobilization of α‐amylase for starch hydrolysis was investigated. Surface morphology, chemical composition, and structural characteristics of the MNPs were analyzed by scanning electron microscopy, energy dispersion spectrometry, and X‐ray diffractometry, respectively. Surface functional groups of MNPs, chitosan‐coated MNPs, and α‐amylase‐immobilized MNPs were characterized by Fourier transform infrared spectroscopy. Response surface methodology based on three levels was implemented to optimize three immobilization conditions and a regression model was developed. α‐Amylase‐immobilized MNPs provided better stability towards pH and temperature. The prepared thermostable nanobiocatalyst is well‐suited for industrial processes involving starch hydrolysis.     

Preparation,characterization and release profiles of pH‐sensitive chitosan beads

Spherical crosslinked beads using chitosan, glycine and glutaraldehyde were prepared for controlled release formulations. Structural investigation of the beads was made with IR analysis. Morphological study of the beads was carried out by scanning electron microscopy. The swelling behaviour of the beads was monitored as a function of time in solutions of different pH. The release experiments were performed using thiamine hydrochloride (Thi‐HCl) as a model drug. These preliminary results suggest the possibility of modifying the formulations to obtain the desired controlled release of drug in an oral sustained delivery system. © 2000 Society of Chemical Industry     

Synthesis and characterization of crosslinked chitosan immobilized on bentonite and its grafted products with polyaniline

Chitosan immobilized bentonite (CIB) namely chitosan‐coated bentonite (5% chitosan content) was synthesized in 2% acetic acid solution, followed by crosslinking, using epichlorohydrien (ECH). The so‐obtained crosslinked chitosan immobilized on bentonite (CIB‐ECH) and CIB composites were grafted with polyaniline (PANI) through oxidative‐radical copolymerization using ammonium peroxydisulfate in acidic medium to produce PANI‐grafted crosslinked chitosan immobilized on bentonite (PANI‐g‐CIB‐ECH) and PANI‐grafted‐chitosan immobilized on bentonite (PANI‐g‐CIB) composites, respectively. The resultant composites were characterized by using X‐ray diffraction (XRD), thermo gravimetric analysis/differential scanning calorimetry, scanning electron microscopy, Fourier transform infrared (FTIR), and electrical conductivity. XRD and FTIR analyses indicate that chitosan was not intercalated into the silicate layer. Also the electrical conductivity elucidates that the grafted composites fall in the range required for the application as electrostatic dissipation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41078.     

Immobilization of yeast alcohol dehydrogenase by entrapment and covalent binding to polymeric supports

Yeast alcohol dehydrogenase (YADH), which catalyzes oxidoreductions of a broad spectrum of substrates, was immobilized by entrapping it into a network of a poly(acrylamide‐co‐hydroxyethyl methacrylate) copolymer and was also covalently bound onto porous chitosan beads activated through glutaraldehyde. Maximum retention of YADH activity achieved was 90 and 24% for entrapment and covalent binding, respectively. The results obtained for thermal, storage, and operational stability of entrapped and covalently bound YADH were compared with free YADH. The immobilized enzyme showed improved thermal and storage stability. The immobilized enzymes also retained 50% activity after six and eight cycles. Enzyme‐catalyzed oxidation of ethanol was observed to be diffusion‐controlled through Lineweaver–Burk plots. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1299–1305, 2001     

Elasticity of ion‐exchange resin beads in solvent mixtures

The effect of the solvent composition on the elasticity of strong and weak cation‐ and anion‐exchange resin beads was studied. Poly(styrene‐co‐divinylbenzene) resins containing sulfonic acid or quaternary ammonium groups and an acrylic acid resin crosslinked with divinylbenzene were immersed in water, NaCl solutions, or aqueous alcohol solutions and the shear modulus was measured with a uniaxial compression method. The elastic data were compared with the swelling properties. In pure water the shear moduli increased when the crosslink density, counterion valence, counterion size, and functional group size increased. Two additional phenomena in the elastic behavior were observed when the swelling degree of the resins was changed by the addition of alcohol or salt. A decrease of the modulus was observed when moving from the fully swollen state to a less swollen state, and a steep upturn of the modulus took place at a characteristic swelling region. The depth of the minimum and the location of the transition from the rubbery to the glassy state depended on the characteristics of the resins. The finite expansibility of the polymer chains and the glass transition explained these findings. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1256–1264, 2001     

Immobilization of β-galactosidase onto polymeric supports

Poly(vinyl alcohol) cross-linked with para-formaldehyde (PVA–F) and natural polysaccharide–chitosan in bead form and salicylic acid–resorcinol–formaldehyde polymeric resin (SRF) in powder form were used for immobilization of β-galactosidase through covalent linkages. Various activation processes and conditions were optimized. Immobilized enzyme showed very good storage stability at room temperature. Durability of the enzyme was also improved on immobilization. On repeated use of enzyme immobilized on chitosan beads, no loss was observed in enzyme activity even after 10 batches. Michaelis constant K_m and maximum reaction velocity V_m were calculated for free and immobilized enzyme systems. Effect of pH and temperature on enzyme activity was estimated and energy of activation (E_a) and inactivation constant (K_i) for free and immobilized enzyme were calculated. © 1995 John Wiley & Sons, Inc.