Intracellular acidification as a mechanism for the inhibition by acid hydrolysis-derived inhibitors of xylose fermentation by yeasts

The main degradation products (furfural, hydroxymethylfurfural, acetate) derived from acid hydrolysis of hemicellulosic materials inhibit growth on and fermentation of xylose by Pachysolen tannophilus and Pichia stipitis, with the latter yeast being the more sensitive. The inhibitory effect was more severe when the inhibitors were present together in the medium. Agarose immobilization partially protected the yeasts from the deleterious effects of these compounds. Intracellular de-energization and acidification may be the mechanism by which these compounds exert their toxic effect on the yeast cells.