Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/27/1998
Publication Date: N/A
Technical Abstract: The production of aldehydes that are microbial inhibitors may occur when hexoses and pentoses are exposed to temperatures above 150 deg C and acid pH in water. These conditions are encountered during pretreatment of biomass in water and acid hydrolysis of biomass. Concentrations of about 0.1% or higher of the degradation products, furfural and hydroxymethyl furfural, strongly inhibit fermentation. This was confirmed when fermentation of the hydrolysate that had not been treated with adsorbent failed. Methods of aldehyde removal that have been tested include sulfite addition to achieve chemical reduction, ion exchange, non-polar solvent extraction, and irreversible adsorption on activated carbon. This paper reports contacting of a polymeric adsorbent, XAS-4, with biomass hydrolysate that contains both furfural and hydroxymethyl furfural. Liquid chromatographic analysis of the remaining effluent showed that aldehyde concentrations were less than 0.01 g/L compared to the initial concentrations that were in the range of 1 to 5 g/L. Fermentation of the resulting sugars with recombinant Escherichia coli ethanologenic strain K011 confirmed that the concentration of aldehydes in the hydrolysate was at a low enough level that the inhibition effect was negligible. Fermentation of treated hydrolysate with E. coli K011 was nearly as rapid as the control medium which was formulated with reagent grade sugars. 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 for removing small amounts of aldehydes that might otherwise result in inhibition of a fermentation.