MEMBRANE FOULING DURING MICROFILTRATION OF PROTEIN MIXTURES

Crossflow microfiltration is an efficient method for the clarification , stabilization and sterilization of fruit juices and other biological suspensions. One of the main problems with the application of this te chnique, however, is membrane fouling caused by the presence of protei ns and polysaccharides. The fouling behavior of four 0.2 mu m hydrophi lic microfiltration membranes (polysulfone, polycarbonate, polyvinylid ene fluoride, and cellulose acetate) is described for protein mixtures of bovine serum albumin (BSA), lysozyme (LY), and ovalbumin (OV). The study of membrane fouling was carried out using a stirred cell, and t hen analyzed with electron microscopy and with flux decline, total res istance and permeate concentration versus time plots. During the filtr ation of single protein solutions using polysulfone and polycarbonate membranes, BSA and LY displayed only internal membrane fouling for a 3 -h period, whereas OV exhibited an initial phase in which internal fou ling dominated, followed by external or surface membrane fouling. When different binary protein mixtures were filtered through the polysulfo ne and the polycarbonate membranes, the highest membrane fouling was f ound for those mixtures containing ovalbumin, Finally, the filtration of a ternary protein mixture showed different fouling behaviors, depen ding on the surface porosities of the four membranes employed; lower s urface porosities exhibited more rapid external membrane fouling.