Lipoprotein lipase (LPL) was covalently immobilized onto the surface of porous chitosan beads (ChB) without or with spacers of different lengths. The relative activity (RA) of the immobilized LPL was found to be high toward a small ester substrate, p-nitrophenyl laurate (pNPL). LPL immobilized with spacer gave an almost constant activity, in marked contrast with the immobilized LPL without spacer, whose activity decreased with decreasing surface concentration. Further, the RA of LPL immobilized with spacer was higher than that of LPL immobilized without a spacer. The pH, thermal, and storage stabilities of the immobilized LPL were higher than those of the free one. LPL immobilized directly to the surface of ChB without any spacer gave a higher stability than that immobilized with spacer, in spite of the lower RA. The spacer effect on RA could be explained in terms of the mobility of the immobilized LPL molecule.
The influence of treating cotton fibres with several amines on the mechanical properties, moisture sorption ability before and after graft polymerization, and on graft yields for various water-soluble and water-insoluble vinyl monomers were analysed. As compared to water, the treatment with amines, ethylenediamine (EDA) in particular, resulted in a decrease in the crystallinity and tensile strength of the cotton fibres, and an increase in the moisture sorption. The graft yields of amine-treated cotton fibres using water-soluble monomers, acrylic acid (AA), methacrylic acid (MAA) and acrylamide (AM) were greater than those observed for watertreated cotton fibres, whereas the graft yields using water-insoluble monomers, methyl acrylate (MA), methyl methacrylate (MMA) and vinyl acetate (VA) were lower. The moisture sorption ability was improved by the graft polymerization with watersoluble monomers. The improvement was enhanced for MA and MAA by treatment with sodium hydroxide to form the corresponding sodium carboxylate derivatives. The tensile strength of EDA-treated cotton was slightly reduced by grafting, while that of the water-activated cotton yarn was barely changed. These results suggest that the graft polymerization of amine-treated cotton fibres with certain vinyl monomers increased the moisture sorption ability without resulting in increased fibre rigidity.
Porous chitosan beads preparing under the wet condition showed specific capacity to adsorb lactoferrin directly from bovine milk by the partial sulfation reactions. Crosslinking of chitosan beads followed by sulfation was found to give much improved stability and the material exhibited excellent property as an adsorbent material for the affinity chromatography of lactoferrin even in case for higher degrees of sulfation. The amount of lactoferrin bound to the column of chitosan beads was effectively enhanced by increasing CSV value (salt splitting capacity per bed volume of beads) untill 100 p eq/mL.
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