Combination of crossflow and electric field for microfiltration of protein/microbial cell suspensions

This work carries out experiments with BSA (Bovine serum albumin)/yeast mixtures by a flat-channel filter imposed with an electric field to investigate effects of electric field strength and electric field modes on filtration rate and protein transmission. The pseudo-steady-state filtration rate measurements were compared with a theoretical model predicted values. Experimental results indicate instantaneous and significant filtration rate changes associated with electric field addition or interruption across the filter chamber. This means that electroosmosis induced in the selected filter medium plays a major role in filtration rate enhancement. Protein transmission through the microfiltration membrane also shows significant enhancement by electric field application to induce electrophoretic migration of the protein toward the membrane.

The characteristics of electrically enhanced crossflow microfiltration for microbial suspensions with protein presence are analyzed. Both electric field strength and pH values give significant influence on filtration rate and protein transmission. For the nylon membrane used, the electroosmotic flux induced in the medium is the dominant contribution to the filtration rate of electrofiltration. In pulsed field mode, the minimum filtration rates per pulse cycle are smaller than that obtained without electric field addition, while under higher electric field strength the maximum filtration rates in pulsed cycle are larger than that obtained from continuous electric field action. When suspension pH is controlled to give an electrophoretic migration of BSA directed to the membrane, protein transmission through the microfiltration membrane enhances significantly.