Flocculation to enhance microfiltration

Tangential flow microfiltration is often used in the manufacture of biopharmaceutical products to separate the cells and cell debris from the growth medium. However, the smaller cellular debris present often fouls the membrane, therefore compromising the permeate flux and reducing the capacity of the microfiltration module. One way of improving the filterability of the feed is to flocculate it thus increasing the average particle size and hence the permeate flux. Here, results are presented for flocculation of yeast suspensions prior to microfiltration using commercially available synthetic polymeric flocculants. Cationic polymers were successful in flocculating the yeast suspensions. Flocculation prior to microfiltration leads to an increase in the permeate flux. An optimum polymer concentration, which maximized the degree of flocculation, was found. Additionally, mixing conditions during flocculation were found to affect the degree of flocculation. Results obtained here show that the average particle size may be used to determine the fouling rate constant during tangential flow microfiltration. (C) 2001 Elsevier Science B.V. All rights reserved.