The Entry of D-Ribose into some Yeasts of the Genus Pichia

Summary: The utilization of d-ribose by yeasts of the genus Pichia was examined with respect to aerobic growth, respiration and entry of ribose into the cells. Pichia etchellsii (CBS2011) could respire d-ribose, but not use it for aerobic growth. Pichiafermentans (CBS187) neither respired nor grew on d-ribose, though it entered the cells of this yeast either by simple diffusion or, possibly, by the d-glucose carrier, this having a very low affinity for d-ribose. Pichia pinus (CBS5097) respired and grew on d-ribose; kinetic evidence is given for this yeast having two ribose carriers, one inducible and the other constitutive.