Protein precipitate recovery using microporous membranes

The use of microporous membranes has been examined for the recovery of precipitated protein suspensions and related soluble protein. Membrane flux rates and soluble protein transmissions are reported for unstirred batch‐cell studies and cross‐flow experiments. The unstirred batch‐cell gave soluble protein transmissions in the range 80–100% for feeds containing either soluble protein or a mix of soluble and isoelectrically precipitated protein. In all cases a sharp decline in flux was observed which was, for example, considerably greater for soluble protein at its isoelectric point, pH 4.6, than at pH 8.8. The presence of precipitated protein led to a further decrease in flux rate. In cross‐flow studies, flux decline was eventually accompanied by a significant decline in soluble protein transmission. The flux protein‐transmission characteristics of microporous membranes are discussed in terms of the interaction of the soluble and precipitated protein with the membrane.