Optical resolution by polymeric membranes is described in terms of molecular designs of membrane materials and permeation behaviors of optically active substrates through various polymeric membranes. Two types of polymeric membranes for optical resolution were characterized. Polymers having optically active bulky groups were reported to separate various optical isomers through chiral interactions within solid membranes. On the other hands, polymers having chiral helix in main chains are also efficient to separate optical isomers. Such polymers derived from poly (L-glutamate) s and poly (pyrrole) dextrane sulfate composite membranes were reported to apply for optical resolution.

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For the preservation of liposomes, freeze-thawing and freeze-drying have been studied by various workers with saccharides (SA) and a freeze-dried liposome preparation is now commercially available. However. the mechanism of stabilizing action of SA in these processes, especially freeze-drying, is not yet fully understood. The interaction of egg yolk phosphatidylcholine (EPC : liquid crystaline state) and DPPC (gel state) liposomes with various glucose oligomers has been studied to elucidate the role of SA in these processes. The stability and property of freeze-dried products were determined by leakage of inner maker, liposomes size and thermal behavior. In the freeze-thawing process of EPC liposome, glucose and maltose are effectively cryoprotective, the large oligomers are not. In the freeze-drying of EPC liposome, glucose is ineffective and maltose is effective, however, oligomers with more than four glucose units are ineffective. As for the DPPC liposome, glucose is less effective and maltose is effective at every SA/PC molar ratio. The large oligomers with more than three glucose units are effective at low SA/PC molar ratio, however, become less effective at higt SA/PC molar ratio. As for the DSC thermograms of freeze-dried products of DPPC and DMPC, the phase transition temperatures (T_c) at first scanning seem to be related with residual water contents of dried product. At second scanning, T_c values move to certain low temperature almost indepenent of the kind of SA. The hydrogen bonding must be formed between SA molecule and PC molecule at first scanning. Based on these results, the role of SA will be discussed focusing on the hydrophilic and hydrophobic character of SA.

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In order to estimate the effects of fouling layer and osmotic pressure on the performance of membrane separation system quantitatively, the concentration polarization equation and the membrane transport equation based on nonequilibrium thermodynamics are applied to membrane processes for liquid foods, and new mathematical models are proposed. The models are applied to some membrane processes for food industry including an ultrafiltration process for cheese whey fractionation, reverse osmosis process for fruit juice concentration, and nanofiltration process for oligosaccharides purification. The efficiency of the membrane processes could be expressed by the new models precisely, and validity of the models are demonstrated. By using these models, some membrane processes for food industry are optimized and their feasibility evaluation is described.

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A calculation method formulated on the basis of both the Donnan equilibrium and the Nernst-Planck equation of flux is presented in order to predict ionic transport across charged membranes in multi-component ionic systems. The method enables us to simulate ionic transport against its concentration gradient. The simulations and the experiments revealed that the maximum ion concentration ratio of the bulk phases at either side of the membrane depends on both the membrnae charge density and the ionic mobility in the membrane. Simulations in a model system of hemodialysis lead to new improved dialysis methods for efficient removal of serum phosphate which utilize a positively charged membrane dialyzer and/or polycation dialysate solution. The calculations of ionic transport across a bipolar membrane in multi-component ionic systems show that the ionic transport against its concentration gradient occurs in the direction either of or opposite to the concentration of the driving ions depending on the values of the mobility of the driving ions and the charge density and thickness of the negative and positive components of the membrane. The permselectivity of the membrane for ionic valence depends on the bipolar direction.

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The investigation of red cell anion exchange protein, band 3 has been at the center of two fundamental questions on functions of membrane proteins : how they regulate cell morphology, and how they regulate homeostasis in the cell and throughout the whole organism. Our recent studies on bovine hereditary band 3 deficiency, a novel disorder inherited in an autosomal dominant mode in which homozygous animals totally lack band 3 due to a nonsense mutation Arg⁶⁶⁴ → stop, have addressed the importance of band 3 in red cell morphology and homeostasis. The animals with total lack of band 3 had red cells that were also deficient in other major membrane skeletal proteins, resulting in a distorted and disrupted membrane skeletal network. Their red cell membranes, therefore, were extremely unstable and showed a continuous loss of surface area, leading to spherocyte formation and anemia. The decreased 4.1a/4.1b ratio implicated a high rate of hematopoiesis compensatory to survive. Rapid anion exchange sensitive to stilbene disulfonate was completely absent in band 3-deficient cells. The animals had slight acidosis and their blood bicarbonate concentration and total CO₂ were lower than control levels but within a normal range, suggesting that there are alternate or multiple strategies for CO₂ and pH homeostasis. These observations demonstrate that band 3 indeed contributes to red cell membrane organization, CO₂ transport, and acid-base homeostasis, but it is not always essential. A putative dominant negative effect of the mutant band 3 protein on expression of functional band 3 is also discussed.

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A diethylamino group as an anion-exchange group was introduced to the poly (glycidyl methacrylate) chain grafted onto a porous hollow-fiber membrane. Subsequently, aminoacylase was adsorbed in multilayers by the graft chains. The enzyme was crosslinked by a reaction with glutaraldehyde to prevent the leakage of the enzyme from the graft chain. Then, an acetyl-DL-methionine solution (pH 8.0) was permeated outward through the aminoacylase-immobilized porous hollow fiber at a permeation rate of 150 ml/h. At a lower feed concentration such as 10 mM, 100% conversion was attained. As the feed concentration was increased, the overall reaction was reaction-controlled. The productivity of L-methionine was maintained at 1, 500μmol/h/ml-fiber up to space velocity of 150 h^-1, where space velocity is defined as effluent volume divided by membrane volume including the lumen.

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Pervaporation separation of benzene/cyclohexane mixtures through polyamide-polyether block copolymer membranes was studied. Benzene was permeated in preference to cyclohexane. Pervaporation performance was greatly dependent not only on polyamide/polyether composition but also on kinds of blocks, polyamide and polyether.

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One of the factors to reduce the performance of a hemodialyzer during clinical treatment is membrane fouling caused by protein adsorption. Highly permeable dialysis membranes recently developed are of asymmetrical structure and the reduction in permeability after protein adsorption may vary with their asymmetrical structure. Intramembrane diffusion coefficients and rejection factor for several solutes of polysulfone membranes having asymmetrical structure were measured before and after plasma protein adsorption. Ratio of intramembrane diffusion coefficient to diffusion coefficient in water for higher molecular weight solutes is reduced after plasma protein adsorption, but that for lower molecular weight solutes is slightly reduced. Rejection factor after plasma protein adsorption increases at lower filtration flux especially for smaller molecules, but that at higher filtration flux hardly changes.

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Bio-fouling resistant RO technology capable of improving water treatment system performance dealing with biologically active surface waters and secondary/tertiary waste water effluents was developed. These bio-fouling resistant RO elements have been tested for the past two years in North America and Europe. Field performance using more than 2, 000 elements demonstrated a significant improvement in system operations. The cleaning frequency at all test locations has decreased by 100% to 300% while showing improvements in stabilized rejection. The new FILMTEC bio-fouling resistant elements are being tested in 4″ and 8″ spiral wound TFC configurations and will be commercially available later in 1998.

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