On-line extraction of ethanol from fermentation broths using hydrophobic adsorbents

Abstract

The effect of removing ethanol during fermentation on the batch kinetics of glucose utilization by the yeast Saccharomyces cerevisiae was examined using several hydrophobic adsorbents. The addition of the molecular sieve, silicalite, to fermentation broths greatly reduced the concentration of ethanol present, but did not increase the glucose utilization rate to the extent predicted by product-inhibition kinetic models obtained from adsorbent-free continuous culture experiments. Addition of two polymeric adsorbents (XAD-4 and XAD-7) greatly inhibited cell growth. This was due to nutrient and cell adsorption by the resin. Adsorption systems were compared to other on-line schemes (vacuferm, solvent extraction) and it was concluded that all of these currently proposed systems would not appear to confer any added advantage if integrated into a high biomass concentration fermenter system. 19 references, 7 figures, 1 table.