Microfiltration (MF) membrane fouling has been a major problem in the process industry. Even though the pore sizes in MF
membranes are generally over an order of magnitude larger than the characteristic size of the protein, there is considerable
experimental evidence that severe fouling occurs and proteins play a critical role in MF fouling. A number of fouling mechanisms
may arise depending upon operational variables, feed and membrane properties. Proteins are complex molecules and a greater
understanding of their conformation, stability and interactions in different membrane environments and under conditions of
shear is crucial to understand and control fouling in these processes. The literature review reveals that protein adsorption is
the first step in the fouling process, although its effect is small on MF membranes. Pore fouling is usually the second step. Pore
fouling appears to be dominated by pore plugging most probably at the pore entrance by aggregates that are present in the feed
or those produced during processing. Protein to pore size ratio seems to be an important factor determining this step. Surface
layer formation or accumulation of protein aggregates on the membrane surface as a third step appears to follow once the MF
membrane pores are completely plugged or covered by protein deposition. The surface layer could be in the form of a gel layer, if
the protein size is much bigger than the pore size and if there are protein-protein interactions. The situation is exacerbated under
high flux conditions apparently due to concentration-induced effects.
Ch.V.V.Satyanarayana obtained PhD in Food Engineering from Massey University, New Zealand. He was a commonwealth Scholar to New Zealand.
He is presently Associate Dean at College of Agril. Engineering, Acharya N G Ranga Agril. University, Madakasira Campus in Anantapur district of
Andhra Pradesh, India.
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