INTRACELLULAR ACIDIFICATION AS A MECHANISM FOR THE INHIBITION BY ACIDHYDROLYSIS-DERIVED INHIBITORS OF XYLOSE FERMENTATION BY YEASTS

The main degradation products (furfural, hydroxymethylfurfural, acetat e) derived from acid hydrolysis of hemicellulosic materials inhibit gr owth on and fermentation of xylose by Pachysolen tannophilus and Pichi a stipitis, with the latter yeast being the more sensitive. The inhibi tory effect was more severe when the inhibitors were present together in the medium. Agarose immobilization partially protected the yeasts f rom the deleterious effects of these compounds. Intracellular de-energ ization and acidification may be the mechanism by which these compound s exert their toxic effect on the yeast cells.