Differential fructose effect in Pachysolen tannophilus and Pichia stipitis

Abstract

The yeasts Pachysolen tannophilus and Pichia stipitis differed in their ability to utilize d‐xylose in the presence of d‐fructose. When P. tannophilus was grown aerobically in a fructose‐xylose mixture, the ketohexose was utilized preferentially over the pentose. However, in P. stipitis cultures, the converse was observed. The effect was associated with the ability of d‐fructose to repress the induction of xylose reductase and xylitol dehydrogenase activities in P. tannophilus but not in P. stipitis. Both yeasts grew on d‐fructose and fermented it to ethanol when it was supplied as the sole carbon source. The results suggest that there may exist some fundamental difference in the regulation of d‐fructose metabolism between P. tannophilus and P. stipitis.