Peroxidase chemically attached on polymeric micelle and its reaction with phenolic compounds.

Horseradish peroxidase was chemically modified with comb-shaped polymaleic anhydride-alt-1-tetradecene (PMA-TD) in microemulsion systems to produce surface-active peroxidase that has capability to form micellar structures in aqueous solutions and can be concentrated at liquid/liquid interfaces without unfolding of the enzyme. For chemical modification oil-in-water (O/W) and water-in-oil (W/O) microemulsion systems composed of n-butyl acetate and a buffer solution were prepared because n-butyl acetate turned out to be less detrimental to the activity of peroxidase at high degree of modification compared to other organic solvents. The modification degree of amine groups on the surface of peroxidase by maleic anhydride groups on PMA-TD was reached at equilibrium after 1h reaction at 0°C, and 42% of amine groups were modified with 7-fold amount of PMA-TD to peroxidase (wt/wt). The activity of the PMA-TD-modified peroxidase measured with 2,4-dichlorophenol at pH 7.0 was increased by approximately 2-fold compared to native peroxidase. There was no significant shift in optimum pH after modification, and optimum pH measured with 2,4-dichlorophenol was observed at pH 7.0. For all six phenolic compounds tested, there was a significant increase in the reaction efficiency with the PMA-TD-modified peroxidase. The remarkable enhancement of the reaction efficiency by the modification was presumably because of micellar structures of PMA-TD that could concentrate hydrophobic phenolic oligomers into the core of the micelles. Overall, horseradish peroxidase chemically attached to the surface of PMA-TD micelles was found to be significantly effective for the oxidative polymerization of phenolic compounds.

Synthesis of chitosan-based polymeric surfactants and their adsorption properties for heavy metals and fatty acids.

Chitosan-based polymeric surfactants (CBPSs) were prepared by N-acylation of chitosans (chitosan 10 and 500) with several acid anhydrides such as hexanoic (C6), lauric (C12), and palmitic (C16) anhydrides. Among the CBPS samples, CBPSs having a good solubility at pH 4.0 were selected and observed for viscosity, surface tension, and adsorption of heavy metals (Cd2+, Co2+, Cr2O7(2-), and Pb2+) as well as the fatty acid (n-octanoic acid). The 1H NMR spectrum of chitosan 10 modified with C16 at the substitution ratio of 0.4 (CBPS10-C16,0.4) showed 85% of acylation in 1% DCl/D2O solutions. CBPS10 with the substitution ratio less than 0.4 showed a good solubility because of shorter repeating units and lesser amounts of hydrophobic substituents. The intrinsic viscosity of CBPS10 was slightly increased, while that of CBPS500 was decreased. As the substitution ratio and length of the carbon chain increased, the surface tension of CBPS10 tended to decrease. CBPS10-C16,0.2 had high adsorption ability for cationic metal ions such as Cd2+, Co2+, and Pb2+ comparable to chitosan. Interestingly, CBPS(10)-C(16,0.2) showed a unique pH optimum for the anionic metal ion such as Cr2O7(2-). In addition, CBPS10-C16,0.2 exhibited the highest adsorption ability for n-octanoic acid among the tested CBPS10 with different carbon chains.

Study on the recovery of phosphorus from waste-activated sludge incinerator ash.

Several batch studies that were made up of the acid extraction and the solvent extraction were performed to recover phosphorus from the waste-activated sludge (WAS) incinerator ash. In the acid extraction, the extraction efficiency of phosphorus relied on the acid type, liquid(acid)-to-solid (L(acid)S) ratio, and acid concentration. Phosphorus in the WAS incinerator ash was completely extracted by 1 M HCl at the L(acid)S ratio of 6.4:1. Subsequently, the solvent extraction was conducted to separate and concentrate phosphorus further from the acid extract. The efficiency of solvent extraction was affected mainly by the solvent type, liquid (solvent)-to-liquid (the acid extract) (L(solv)L(acid ext)) ratio, and hydrogen ion concentration. Under the appropriate condition, 76% of phosphorus in the acid extract was extracted to 1-butanol phase, which corresponded to 80.1% as the mass fraction of phosphorus to total elements. Prior to the solvent extraction, the addition of bis (2-ethylhexyl) phosphoric acid (D2EHPA), which was available for removing aluminum from the acid extract, led to an additional increase in the term of the mass fraction of phosphorus to total elements. Overall results indicated that phosphorus in the WAS incinerator ash could be efficiently recovered and be a potential renewable resource.

pH- and temperature-sensitive release behaviors from polyelectrolyte complex films composed of chitosan and PAOMA copolymer.

This paper describes the pH and temperature effects on drug release from polyelectrolyte complex (PEC) films composed of a cationic polymer, chitosan, and an anionic polymer, polyalkyleneoxide-maleic acid copolymer (PAOMA). In this study, we prepared and investigated PEC films in terms of the drug release properties as pH- and temperature-sensitive drug carriers. Drug release rates were tested at pH 3.8 and 7.2, and at 25 and 50 degrees C. Salicylic acid and phenol were selected as model drugs. An increase in pH from 3.8 to 7.2 resulted in an increase in the rate of drug release because of the repulsive forces between carboxyl groups in PAOMA and anionic groups in model drugs. When the hydrophobic PAOMA was used as a polyanion, the drug release rate increased at 50 degrees C. This is attributed to the increase of release area due to the phase transition of PAOMA and the increase of repulsive forces between carboxyl groups in PAOMA and anionic groups in model drugs.

Polyelectrolyte complex films derived from polyethyleneoxide-maleic acid copolymer and chitosan: preparation and characterization.

Polyelectrolyte complex films were prepared with polyethyleneoxide-maleic acid copolymer and chitosan using a casting/solvent evaporation method. The films were examined in terms of their IR spectra, surface and cross-section morphologies, cytotoxicity, and swelling behavior at different pH levels. To assess the potential of these films as a biomedical device, the profiles of the release of model drug from the CS/PEOMA films were examined at pH 4.8. The surface morphology of the films was quite smooth and uniform, and the cross-sectional morphology was dense and homogeneous. The swelling behaviors of CS/PEOMA films were found to depend on the pH of the solution as well as on the CS/PEOMA composition. Drug release from different CS/PEOMA films at pH 4.8 was found to be dependent on film composition. The results showed the potential applicability of CS/PEOMA film as a drug delivery vehicle.

Inhibitory effect of high molecular weight water-soluble chitosan on hypoxia-induced inflammatory cytokine production.

Chitosan is widely used to treat patients with hypoxia-induced diseases such as ischemia, neuronal death, cerebral stroke, and cerebral infarction. Using the ELISA method, we examined the effect of high molecular weight water-soluble chitosan (WSC) on inflammatory cytokine production in the desferrioxamine (DFX, known to mimic hypoxia)-stimulated human mast cell line HMC-1. DFX significantly increased interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-alpha production compared with the control in a time-dependent manner (p<0.05), but did not affect IL-1alpha production and mRNA expression. The increase in IL-6, IL-8, and TNF-alpha levels was significantly inhibited by WSC in a dose-dependent manner with IC(50) values of 0.77, 0.88, and 2.5 microg/ml, respectively. The maximal inhibition rate of IL-6, IL-8, and TNF-alpha production by WSC was 64+/-9.7%, 80+/-9.4% and 54+/-4.5%, respectively. In addition, WSC inhibited DFX-induced activation of nuclear factor (NF)-kappaB. In conclusion, these results suggest that WSC is an inhibitor of NF-kappaB under hypoxic conditions, which might explain its beneficial effect in the treatment of hypoxia-induced inflammatory diseases.

Evaluation of remediation process with plant-derived biosurfactant for recovery of heavy metals from contaminated soils.

A washing process was studied to evaluate the efficiency of saponin on remediating heavy metal contaminated soils. Three different types of soils (Andosol: soil A, Cambisol: soil B, Regosol: soil C) were washed with saponin in batch experiments. Utilization of saponin was effective for removal of heavy metals from soils, attaining 90-100% of Cd and 85-98% of Zn extractions. The fractionations of heavy metals removed by saponin were identified using the sequential extraction. Saponin was effective in removing the exchangeable and carbonated fractions of heavy metals from soils. In recovery procedures, the pH of soil leachates was increased to about 10.7, leading to separate heavy metals as hydroxide precipitates and saponin solute. In addition recycle of used saponin is considered to be effective for the subsequent utilization. The limits of Japanese leaching test were met for all of the soil residues after saponin treatment. As a whole, this study shows that saponin can be used as a cleaning agent for remediation of heavy metal contaminated soils.