Recent ultrastructural studies have revealed certain topographical characteristics of intestinal microvillar membrane proteins. When viewed by electron microscopy of conventional thin sections prepared from isolated microvilli, the external surface of the membrane is very poorly overlaid with fuzzy structures. However, negative staining electron microscopy shows that the external surface is studded with numerous dimeric particles and sometimes with doughnut-shaped particles, which are known to be hydrolytic enzymes abundant in the microvillar membrane. The freeze-fracture faces of the microvillar membrane numerous intramembrane particles, which are presumed to represent integral membrane proteins, e.g. transporters. The large part of the present review is concerned with the hydrolytic enzymes, especially sucrase-isomaltase complex, the enzyme most studied ultrastructurally. The hydrolytic enzymes have certain common structural features. They consist of two similar or dissimlar subunits, though a few exceptions are known. The major hydrophilic part of the molecule contains the enzymic active site and protrudes from the external surface. The minor hydrophbic domain is responsible for anchoring the molecule to the membrane and located near the amino terminus of the polypeptide chain. It is likely that for the symmetric enzymes, e.g. pig aminopeptidases A and M both subunits are associated with the membrane, while for the asymmetric enzymes, e.g. sucrase-isomaltase complex and gamma-glutamylpeptidase only one subunit is bound to the membrane. The relationship between the microvillar membrane proteins and the core cytoskeleton remains to be elucidated

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During the last fifteen years, membrane technology in the world dairy industry has been developed so much that 100, 000m² area of UF membrane is used nowadays.
The main reason of this development is due to the worldwide whey problem. Also, UF cheese production by the MMV method has been successfully industrialized.
In this paper the membrane technology was birds-eye-viewed in a chart and its structure was diagrammed. According to this diagram UF and RO were reviewed. And a Japanese milk products company's whey problem and involvement in membrane technology were briefly intro-duced.

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A review on reverse osmosis membranes was carried out with over 60 references which appeared after 1980 on Journal of Applied Polymer Science, Journal of Membrane Science, Desalination, International Symposiums on this subject, and other several Journals. The topics selected were membranes derived from polyvinylalcohol, composite membranes, and cellulose acetate membranes. Morphology, membrane life and properties of cellulose acetate membrane were par-ticularly reviewed.

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The relationship between the structures of synthetic noncyclic polyether carriers and their ability of the selective ion-transport through liquid membranes has been discussed. It has been demonstrated that cation selective transport by these carriers depends largely upon the kinds of both chain structures and end groups. On the basis of the CPK model building, together with their structural information, it has been suggested that both the formations of the pseudocavity, of which size depends upon the chain structures of their polyethers, and the hydrophobic external wall formed by the stacking between the end aromatic rings are important to exhibit cation selective transport. Spectroscopic behaviors of their alkali salts have been also investigated to verify the stacking.

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Reverse osmotic concentration of aqueous propionic acid and citric acid solutions were carried out using composite membrane PEC-1000 supplied from Toray Co. Ltd.,
Separation of propionic acid and citric acid, and flux through the membrane were measured under the following conditions : concentration of propionic acid, 2.28, 4.67, 9.25, 12.3wt%, concentration of citric acid, 2, 4.3, 9, 12.3wt%, operating pressure, 2.94, 3.92, 5.49, 6.86Mpa. The measured separations of propionic acid were always above 94% and those of citric acid above 99.95%.
An analysis of data with Spiegler-Kedem's transport model shows that the value of reflection coefficient σ, soulute and hydraulic permeabilities ω and L_p for propionic acid were 0.988, 2×10^-11, 8.15×10^-8, (mol/m² pa. s), respectively, and those for citric acid 1.0, . 033×10^-11, 8.52×10^-8 (mol/m²pa. s) respectively.
Energy and membrane area required were calculated to concentrate dilute propionic acid and citric acid solutions by reverse osmosis. The energy per one kilogram of concentrated propionic acid is propotional to pressure difference and depends on the final concentration and concentration polarization, and found 0.3 and 0.7 kwh/kg-PAc at 5 and 10 MPa respectively to concentrate up to 14.7wt% from 0.5wt%. The energy of concentrated citric acid is proportional to pressure difference and independs on the concentration polarization. The area for two solutions are inversely propotional to operating pressure, and found to be 0.2-0.9m²/ (kgPAc/day), 0.06-0.2m²/ (kgCAc/day).

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The purpose of this paper is to apply the method of circuit model synthesis to a complicated system, and to simulate the irreversible process of the membrane transport system. In the circuit model, the necessary powers for the membrane transport are supplied by the idel capacitors, of which the potentials decrease during the transport process. Their potential changes are expressed from the volume, concentrations and their changes in the compartmental solution The set of transport equations derived from the circuit model and of the equations for the potential changes provides the simultaneous ordinary differential equations for the system simulations. We synthesized the circuit model of the coupled water and ionic transport system. 'Using this model, the mechanism and the role of voltage depended electro-osmosis are clarified. The irreversible processes untill the Donnan's equilibrium state were simulated with computer calculations.

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