YEAST SUSPENSION FILTRATION - FLUX ENHANCEMENT USING AN UPWARD GAS LIQUID SLUG FLOW - APPLICATION TO CONTINUOUS ALCOHOLIC FERMENTATION WITHCELL RECYCLE/

This study deals with the use of an upward gas/liquid slug flow to red uce tubular mineral membrane fouling. The injection of air into the fe edstream is designed to create hydrodynamic conditions that destabiliz e the cake layer over the membrane surface inside the filtration modul e complex. Experimental study was carried out by filtering a biologica l suspension (yeast) through different tubular mineral membranes. The effects of operating parameters, including the nature of the membrane, liquid and gas flowrates, and transmembrane pressure, were examined. When external fouling was the main limiting phenomenon, flux enhanceme nts of a factor of three could be achieved with gas sparging compared with single liquid phase crossflow filtration. The economic benefits o f this unsteady technique have also been examined. To investigate the possibility of long-term operation of the two-phase flow principle, de nse cell perfusion cultures of Saccharomyces cerevisiae were carried o ut in a fermenter coupled with an ultrafiltration module. The air inje ction allowed a high and stable flux to be maintained over 100 h of fe rmentation, with a final cell concentration of 150 g dry weight/L. At equal biomass level, a twofold gain in flux could be attained compared with classical steady crossflow filtration at half the cost. (C) 1998 John Wiley & Sons, Inc.