D-Xylose transport by Candida succiphila and Kluyveromyces marxianus

The kinetics and regulation of D-xylose uptake were investigated in the efficient pentose fermentor Candida succiphila, and in Kluyveromyces marxianus, which assimilate but do not ferment pentose sugars. Active high affinity (Km approximately 3.8 mM; Vmax approximately 15 nmol/[mg min]) and putative facilitated diffusion low-affinity (Km approximately 140 mM; Vmax approximately 130 nmol/[mg min]) transport activities were found in C. succiphila grown, respectively, on xylose or glucose. K. marxianus showed facilitated diffusion low-affinity (Km approximately 103 mM; Vmax approximately 190 nmol/[mg min]) transport activity when grown on xylose under microaerobic conditions, and both a low-affinity and an active high-affinity (Km approximately 0.2 mM; Vmax approximately 10 nmol/[mg min]) transport activity when grown on xylose under fully aerobic conditions.