Characteristics of Ovalbumin Gel Layer Formed on Ceramic Microfiltration Membranes

Abstract

Ovalbumin solution, which is known to form a gel layer on membrane surfaces, was filtrated in a cross-flow mode using ceramic microfiltration membranes. The influences of pH and ionic strength of the ovalbumin solution on the properties of the gel layer and membrane permeability were studied.
At a pH near the isoelectric point of the ovalbumin solution, both the permeate flux and ovalbumin rejection showed the lowest value. The cohesion force acting among ovalbumin molecules became strongest because the electrostatic repulsion force among the molecules was weakened, and then the gel layer was tightly adsorbed onto the membrane surface. Therefore, the membrane permeate flux obtained at the pH of the isoelectric point was smaller than that obtained at the other pH. The ovalbumin rejection increased at the other pH, except for the isoelectric point, because of the electrostatic repulsion of the ovalbumin gel layer formed on the membrane surface. The influence of electric charge was also recognized in the case of the filtration of sodium L-glutamate solution using the ovalbumin gel layer.
When the ovalbumin solution was filtered with a high ionic strength, the permeate flux and the ovalbumin rejection were almost constant, independent of the solution pH.
The molecular weight cut-off values of the ovalbumin gel layer were about 200,000–300,000 as self-rejecting dynamic membranes.
The specific resistance of the ovalbumin gel layer obtained in dead-end filtration increased in pH near the isoelectric point and with increasing ionic strength of the feed solution. This tendency of the specific resistances was in good agreement with the behavior of the permeate flux of the ovalbumin solution.