FOULING EFFECTS OF YEAST CULTURE WITH ANTIFOAM AGENTS ON MICROFILTERS

The fouling effects of yeast fermentation broths of Candida utilis in the presence of various commercial antifoam agents (PPG2000, B5600, an d G832) up to 4.0 mL/L were studied, using Millipore polyvinylidene fl uoride 0.22-mu m hydrophilic membranes (GVWP), in a stirred-cell syste m at 50 kPa and 700 rpm. PPG2000, which has a low value of work of adh esion (W-a of 0.81 mN/m), gave a steady flux of broth of 29 L/(h m(2)) and was found to have no significant fouling effect on the microfiltr ation of broth. G832, which has a high W-a, (26.0 mN/m) reduced the fl ux of the broth to 17 L(h m(2));i.e., by 42% when only 1.0 mL/L was us ed. However, B5600, which has a W-a of 14.3 mN/m, was found to enhance the flux of broth to 54 L/[h m(2)); i.e., by 86%, due to the preferen tial adsorption of the B5600 components onto the hydrophobic cell cont ents released. These results were reinforced by the depressurization e xperiments performed with both hydrophilic (GVWP) and hydrophobic (GVH P) membranes, using both young and aged broths. B5600 was found to be the optimum antifoam agent in this study in terms of membrane performa nce and defoaming efficiency. (C) 1997 John Wiley & Sons, Inc.