Detoxification of lignocellulose hydrolysates with ion-exchange resins

Lignocellulose hydrolysates contain fermentation inhibitors causing decreas ed ethanol production. The inhibitors include phenolic compounds, furan ald ehydes, and aliphatic acids. One of the most efficient methods for removing inhibiting compounds prior to fermentation is treatment of the hydrolysate with ion-exchange resins. The performance and detoxification mechanism of three different resins were examined: an anion exchanger, a cation exchange r, and a resin without charged groups (XAD-8). A dilute acid hydrolysate of spruce was treated with the resins at PH 5.5 and 10.0 prior to ethanolic f ermentation with Saccharomyces cerevisiae. In addition to the experiments w ith hydrolysate, the effect of the resins on selected model compounds, thre e phenolics (vanillin, guaiacol, and coniferyl aldehyde) and two furan alde hydes (furfural and hydroxymethyl furfural), was determined. The cation exc hanger increased ethanol production but to a lesser extent than XAD-8, whic h in turn was less effective than the anion exchanger. Treatment at VH 10.0 was more effective than at PH 5.5. At pH 10.0, the anion exchanger efficie ntly removed both anionic and uncharged inhibitors, the latter by hydrophob ic interactions. The importance of hydrophobic interactions was further ind icated by a substantial decrease in the concentration of model compounds, s uch as guaiacol and furfural, after treatment with XAD-8.