Native yeast is cannot ferment xylose to ethanol; this yeast can ferment xylulose and xylose to ethanol. D-xylose isomerase is used to isomerize xylose to xylulose. The chemical equilibrium for this reaction is unfavorable for xylulose production, with an equilibrium ratio of ~2:8 xylulose:xylose at pH 7.A class of complexing agents, aryl boronic acids (ABAs), can exhibit pH-dependent partitioning for aqueous and organic phases. At high pH (>7.5), ABAs exist predominantly in their conjugated base form and are able to bind with polyols to form a tetragonal ester that is significantly more water-soluble than the conjugated base form. When the pH of the aqueous medium is low (<5), the ABAs exist predominantly in the un-ionized conjugate acid form which is not able to complex with polyols. This pH-dependent complexation of ABAs to polyols and the hydrophobic/hydrophilic transition provide a method of recovery for ABAs via a two-phase extraction scheme.

Methods for simultaneous xylose isomerization and separation: Concentration of xylose and xylulose by phase switching

243rd National Meeting (2012)

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