IDENTIFICATION OF INHIBITORY COMPONENTS TOXIC TOWARD ZYMOMONAS-MOBILIS CP4(PZB5) XYLOSE FERMENTATION

Zymomonas mobilis CP4(pZB5) is a recombinant bacterium that can produc e ethanol from both xylose and glucose. The ethanol-producing efficien cy of this organism is substantially impeded by toxic substances prese nt in pretreated hydrolyzates or solid biomass substrates. Acetic acid and furfural (a pentose degradation product) are highly toxic to this organism at levels envisioned for a pretreated-hardwood liquid hydrol yzate. in addition, lignin degradation products and 5-hydroxymethylfur fural (a hexose degradation product) have a moderately toxic effect on the organism. Of the compounds studied, organic acids and aldehydes w ere found to be more inhibitory than lignin acids or the one alkaloid studied. Acetone:water and methanol extracts of solid biomass samples from red oak, white oak, and yellow poplar are toxic to Zymomonas cell growth and ethanol production, with the extracts from white oak being the most toxic.