High capacity xylose transport in Candida intermedia PYCC 4715

Xylose-utilising yeasts were screened to identify strains with high xylose transport capacity. Among the fastest-growing strains in xylose medium, Candida intermedia PYCC 4715 showed the highest xylose transport capacity. Maximal specific growth rate was the same in glucose and xylose media (mu(max) = 0.5 h(-1), 30degreesC). Xylose transport showed biphasic kinetics when cells were grown in either xylose- or glucose-limited culture. The high-affinity xylose/proton symport system (K-m = 0.2 mM, V-max = 7.5 mmol h(-1) g(-1)) was more repressed by glucose than by xylose. The less specific low-affinity transport system (K = 50 mM, V-max = 11 mmol h(-1) g(-1)) appeared to operate through a facilitated-diffusion mechanism and was expressed constitutively. Inhibition experiments showed that glucose is a substrate of both xylose transport systems. (C) 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.