The production of aldehydes that are microbial inhibitors may occur when hexoses and pentoses
in an aqueous solution are exposed to temperatures above 150 °C under acidic conditions common
to acid-catalyzed lignocellulose biomass pretreatment. Concentrations greater than 0.1% of the
degradation product, furfural, strongly inhibit fermentation, as was confirmed for hydrolysate
that contained 0.5% (w/o) furfural. Methods of furfural removal that have been reported include
sulfite or alkali addition to achieve chemical reduction, ion exchange, hydrophobic adsorption,
and irreversible adsorption on activated carbon. This paper reports the removal of furfural from
biomass hydrolysate by a polymeric adsorbent, XAD-4, and desorption of the furfural to
regenerate the adsorbent using ethanol. Liquid chromatographic analysis showed that furfural
concentrations were less than 0.01 g/L compared to the initial concentrations that were in the
range of 1−5 g/L. Fermentation of the resulting biomass hydrolysate with recombinant
Escherichia coli ethanologenic strain K011 confirmed that the concentration of furfural in the
hydrolysate caused negligible inhibition. Fermentation of XAD-4-treated hydrolysate with E.
coli K011 was nearly as rapid as the control medium that was formulated with reagent-grade
sugars of the same concentration. Ethanol yields for both fermentations were 90% of theoretical.
Modeling of the adsorptive properties of this styrene-based adsorbent indicates that it is suitable
for on−off chromatography and could be useful in a continuous processing system for removing
small amounts of aldehydes that might otherwise inhibit fermentation.