Yasuhito Mukai

Upward Dead-End Ultrafiltration of Binary Protein Mixtures

Abstract Upward dead-end ultrafiltration of aqueous solutions of mixtures of bovine serum albumin (BSA) and egg white lysozyme was conducted using membranes which are almost completely retentive for BSA but permeable for lysozyme. The dependence of lysozyme rejection and the filtration flux rate on pH and the addition of salts has been investigated. The experimental data obtained in this study clearly demonstrate that the electrostatic interactions between dissimilar molecules may control the solute rejection and the filtration rate in upward ultrafiltration of binary protein mixtures. For instance, the BSA and lysozyme molecules have opposite electric charges at pH 7. Consequently, lysozyme rejection is large because both molecules within the filter cake pack more tightly due to heterocoagulation. On the other hand, the BSA and lysozyme molecules have the same electric charge at pH 4. Thus, lysozyme is rejected by the filter cake of the retained BSA molecules due to repulsive electrostatic interactions b...

Flux decline behavior in dead-end microfiltration of protein solutions

Constant pressure microfiltration of solutions of the protein bovine serum albumin (BSA) has been studied in a batch filtration cell without stirring. Flow resistance increased dramatically with time compared with the initial membrane resistance while most of the solutes passed through the membrane. The variation of the filtration flux rate with time during extended filtration periods could not be analysed by a unique blocking filtration law. The long-term decline in the filtration rate was accurately described by considering the variation of the value of the exponent i in the general characteristic form of the blocking filtration laws. It was found that the value of i continued to decrease with the progress of filtration. In addition, the effects on the filtration rate due to the solution pH, the filtration pressure, the fluid solute concentration, and the membrane type were described based on the general characteristic form of the blocking filtration laws.

Separation of binary protein mixtures by ultrafiltration

Ultrafiltration of aqueous solutions of mixtures of bovine serum albumin(BSA) and egg white lysozyme was conducted using membranes which were almost completely retentive for BSA, but permeable for lysozyme, in order to investigate the factors influencing the filtration rate and the lysozyme rejection. The experimental data obtained in this study clearly demonstrate that the electrostatic interactions between dissimilar molecules may control the filtration rate and solute rejection in ultrafiltration of binary protein mixtures to a significant degree. It is also shown that increasing the shear stress acting on the membrane causes an increase in the lysozyme rejection, resulting in a reduced fractionation efficiency, and that ultrasonic irradiation is quite effective for fractionation of binary protein mixtures. Furthermore, the properties of the filter cake formed on the retentive membranes in downward dead-end ultrafiltration of binary protein mixtures have been studied in a batchwise filter which has a sudden reduction in its filtration area. In the pH range where both proteins are electropositive, the filter cake becomes loose and wet, thus reducing the flow resistance, while the cake becomes compact and dry in the pH range where the two proteins have opposite electrical charges.

Fractionation Characteristics of Binary Protein Mixtures by Ultrafiltration

ABSTRACT Ultrafiltration (UF) of mixtures of bovine serum albumin (BSA) and egg white lysozyme was conducted using membranes which were almost completely retentive for BSA but permeable for lysozyme. The experimental data have clearly demonstrated that the separation properties of binary protein mixtures are largely influenced by the hydrodynamics above the membrane, the solution environment, and the adsorption of the protein solutes within the membrane. In particular, it must be noted that the increase of the shear stress acting on the membrane surface improves the filtration rate, but causes the increase of the lysozyme rejection, resulting in a reduction in the fractionation efficiency. Furthermore, the effects of ultrasonic irradiation on the UF properties have been tested experimentally. Although the filtration rate was enhanced significantly by ultrasonic irradiation, the lysozyme rejection remained unchanged. The results showed that ultrasonic irradiation is quite effective for protein fractionation.

Effect of protein charge on cake properties in dead-end ultrafiltration of protein solutions

Abstract The properties of the filter cake formed on the retentive membrane in dead-end ultrafiltration of bovine serum albumin (BSA) solutions were obtained by using a batchwise filter which had a sudden reduction in its filtration area. Moreover, the zeta potential of BSA was measured by the electrophoretic light scattering method in order to investigate the correlation with the properties of the protein cake. The experimental data clearly demonstrated that the plots of such properties of the filter cake as the average porosity ɛav and the average specific filtration resistance αav against the absolute value of the zeta potential can almost be represented by a unique curve, respectively, irrespective of the sign of the zeta potential.

Analysis of Gravity Filtration Behaviors of Waterworks Sludge Based upon Sedimentation Tests

Both gravity filtration experiments under constant pressure conditions and gravity sedimentation experiments were conducted using the municipal waterworks sludge. It was clarified from the theoretical analysis that the effect of sedimentation on the filtration rate was noticeable for the sludge used in this study. The local specific flow resistance at various sludge concentrations was determined by the sedimentation velocity method. The local porosity was related to the local solid compressive pressure by the sedimentation equilibrium method. The decline behaviors in the filtration rate in gravity filtration accompanied by sedimentation were well evaluated only from the sedimentation data based upon the sedimentation velocity method and the sedimentation equilibrium method.

APPROACH FROM PHYSICOCHEMICAL ASPECTS IN MEMBRANE FILTRATION

In membrane filtration, solution environment factors such as pH and solvent density are important in controlling the filtration rate and the rejection of the particles and/or the macromolecules. The filtration rate and the rejection in membrane filtration have been investigated from physicochemical aspects. It was shown that the properties of the filter cake formed on the membrane surface play a vital role in determining the filtration rate in mem-brane filtration. It was clearly demonstrated that such filtration behaviors as the filtration rate and the rejection are highly dependent on the electrical nature of the particles and/or the macromolecules. Furthermore, it was shown that the solvent density ρ has a large effect on the steady filtration rate in upward ultrafiltration.

Characteristics of filter cake exfoliation in upward ultrafiltration of nanoparticle suspensions.

Downward and upward ultrafiltration (UF) was performed using the suspensions of nanosized colloidal silica with different particle diameters and their filtration rates were compared. In downward UF, the filtration rate decreases as the particle diameter decreases because the specific filtration resistance of the filter cake becomes significantly higher. In contrast, the filtration rate in upward UF increases with the decrease in the particle diameter because the filter cake consisting of small particles is exfoliated much more easily under the influence of gravity than that of large ones. In order to evaluate the characteristics of the filter cake exfoliation, the steady filtration rate in the upward mode was measured. The steady filtration rate has a tendency to decrease with particle concentration as well as mean particle diameter. Therefore, when the small particles are added into a given concentration of large particle suspension, the mean particle diameter decreases and the total particle concentration increases due to the dosage of small particles. This results in a maximum of the steady filtration rate at a certain dosage of small particles. Moreover, an estimation equation was proposed for predicting the steady filtration rate in upward UF of colloidal silica suspensions with various mean particle diameters and total particle concentrations.